Difference between revisions of "Evolutionary origin of human traits"

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== Rationale ==
 
== Rationale ==
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=== Hypotheses ===
  
 
There are conflicting hypotheses to explain why the traits that so clearly distinguish humans from other primates originally evolved. One idea is that the ancestors of humans came to live in a different kind of environment than the ancestors of chimpanzees and gorillas, and hence experienced different selection pressures and obtained a suite of unique traits as adaptations to the new environment. What that new environment was and which selection pressures were most important has been debated, however, and a number of hypotheses based on ideas other than environmental adaptation have also been proposed. To date, general discussion on the topic seems mostly to have focused on finding merit or flaws in one hypothesis at a time. The purpose of this page is to provide a structured forum for the general evaluation and comparison of the different hypotheses on human origins.
 
There are conflicting hypotheses to explain why the traits that so clearly distinguish humans from other primates originally evolved. One idea is that the ancestors of humans came to live in a different kind of environment than the ancestors of chimpanzees and gorillas, and hence experienced different selection pressures and obtained a suite of unique traits as adaptations to the new environment. What that new environment was and which selection pressures were most important has been debated, however, and a number of hypotheses based on ideas other than environmental adaptation have also been proposed. To date, general discussion on the topic seems mostly to have focused on finding merit or flaws in one hypothesis at a time. The purpose of this page is to provide a structured forum for the general evaluation and comparison of the different hypotheses on human origins.
 +
 +
Below you can find a list of hypotheses explaining different traits that separate humans from other great apes. They were a part of a survey done on people's understanding about the reasons behind human traits, answered by paleontologist, biologists, medical professionals, and other people with professional understanding about evolution (human or in general) or how human bodies work. Some analysis done on the survey answers can be found below. Some hypotheses much discussed in literature in the last years are missing from the survey (and thus he list below), such as the [[:en:Bipedalism#Postural feeding hypothesis|postural feeding hypothesis]], stating bipedalism originally arose as a feeding posture and not as a way of locomotion, and the expensive tissue hypothesis, which suggests the energy needed for building a big brain came from reducing some other expensive tissue in our body, namely the gut. A literary review was done on the same hypotheses asked about in the survey to find out whether the understanding about human evolution the answerers had was the same that could be gotten from scientific literature published in the last decades. Some analysis on the literary review results is found on this page.
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The short version of the hypotheses in the list below are the ones used to refer to them in the analysis.
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 +
{| {{prettytable}}
 +
|+'''Hypotheses and their shorter versions
 +
|---
 +
! For short !! Hypothesis
 +
|---
 +
|colspan="2"| '''Bipedalism
 +
|---
 +
| Energy efficiency || When covering long distances on the ground, walking or running erect on two legs is energetically more efficient than walking or running on four legs.
 +
|---
 +
| Thinner branches || In the canopy, walking erect facilitates using multiple supports (as in orangutans) and hence makes it possible to move on thinner branches than when brachiating or moving quadrupedally.
 +
|---
 +
| Wading || In a littoral habitat, walking erect allows wading in deeper water with the nostrils above the surface (apes cross water bodies bipedally), and the same posture increases streamlining when swimming and diving for food (as in penguins).
 +
|---
 +
| Thermoregulation-b || Walking erect helps in thermoregulation in the savanna by exposing less skin to the midday sun and more skin to cooling wind.
 +
|---
 +
| Better view || Walking erect makes it possible to see above the savanna grass and hence spot danger from further away.
 +
|---
 +
| Foraging || Walking erect makes foraging more efficient, because hands are not needed for locomotion.
 +
|---
 +
| Carrying food || Walking erect makes it easier for a male to carry high-quality food such as meat to the female and infants.
 +
|---
 +
| Carrying baby || Walking erect makes it possible for a female to carry its offspring in its arms.
 +
|---
 +
| Tool use || Walking erect makes it easier to use tools and weapons.
 +
|---
 +
| Genitals || Walking erect is favored by sexual selection, as it makes the genitals more visible.
 +
|---
 +
|colspan="2"| '''Big brain
 +
|---
 +
| Meat || A shift in diet towards eating more meat triggers encephalization, because meat is rich in energy.
 +
|---
 +
| Fish || A shift in diet towards eating more fish and other seafood triggers encephalization, because seafood is rich in both energy and the omega-3 fatty acids that are an essential component of brain tissue.
 +
|---
 +
| Cooking || The use of fire triggers encephalization, because cooking increases the nutritional value of plant foods.
 +
|---
 +
| Social || Complex social organization causes pressure for greater intelligence and hence triggers encephalization.
 +
|---
 +
| Collaborative hunting || Collaborative hunting causes pressure for greater intelligence and hence triggers encephalization.
 +
|---
 +
| Language || Spoken language causes pressure for greater intelligence and hence triggers encephalization.
 +
|---
 +
| Warfare || Warfare causes pressure for greater intelligence and hence triggers encephalization.
 +
|---
 +
| Neoteny || Encephalization is a secondary effect of neoteny (the retention of juvenile features into adulthood), which is advantageous when specialized adult morphology adapted to one environment has become maladaptive in a new environment.
 +
|---
 +
| Bipedalism-b || Encephalization is triggered by bipedalism, which changes the blood circulation and provides a cooling mechanism for the larger brain.
 +
|---
 +
| Nakedness || Encephalization is triggered by nakedness, which provides a cooling mechanism for the larger brain.
 +
|---
 +
|colspan="2"| '''Nakedness
 +
|---
 +
| Skin contact baby || Direct skin-to-skin contact strengthens the emotional bond between a female and its nursing offspring.
 +
|---
 +
| Skin contact sex || Direct skin-to-skin contact makes sex more enjoyable, and is favored by sexual selection.
 +
|---
 +
| Cleanliness || In animals that feed messily on carrion, naked skin stays cleaner than hairy skin (or feather-covered skin as in vultures).
 +
|---
 +
| Ectoparasites || In mammals that live in permanent nests, naked skin helps to avoid a high ectoparasite load.
 +
|---
 +
| Drag || In mammals that live partly or entirely entirely in water, fur is often lost because it causes drag when swimming but fails to provide efficient insulation when wet (e.g. walrus, hippopotamuses, dolphins).
 +
|---
 +
| Thermoregulation-h || In mammals that hunt on the savanna, naked skin dissipates heat more efficiently and reduces the risk of becoming overheated.
 +
|---
 +
| Large mammal || Large mammals can regulate their body temperature without investing in hair, and humans are relatively large compared to other primates.
 +
|---
 +
| Clothes || Once the use of clothes has become common, fur becomes unnecessary.
 +
|---
 +
|colspan="2"| '''Subcutaneous fat
 +
|---
 +
| Energy supply || In conditions of variable food supply, subcutaneous fat can store energy for times of food scarcity, and in infants it secures the development of the large brain.
 +
|---
 +
| Insulation || In wet conditions, subcutaneous fat provides more efficient insulation than hair does, and it makes swimming easier by increasing buoyancy and streamlining of the body.
 +
|---
 +
| Savannah thermoregulation || Subcutaneous fat is an adaptation to thermoregulation in the savanna, together with nakedness and sweating.
 +
|---
 +
| Body shape || Subcutaneous fat defines the body shape and its evolution is driven by sexual selection.
 +
|---
 +
|colspan="2"| '''Descended larynx
 +
|---
 +
| Articulation || Articulate speech requires a descended larynx, because this makes it possible to produce a wider variety of sounds.
 +
|---
 +
| Impressive voice || A descended larynx makes the voice stronger and more impressive, and can evolve through sexual selection (as in the males of some deer).
 +
|---
 +
| Diving-l || A descended larynx can evolve as an adaptation to diving (as in some aquatic mammals), because it makes it possible to close the air passages when under water and to inhale rapidly through the mouth when surfacing.
 +
|---
 +
|colspan="2"| '''Speech
 +
|---
 +
| Larynx || Speech is triggered by the descended larynx, which allows making a wider variety of sounds.
 +
|---
 +
| Diving-s || Speech requires voluntary breath control, which can evolve as an adaptation to diving. In water, visual and olfactory cues are inadequate and therefore liable to be replaced by vocal communication (as in whales).
 +
|---
 +
| Bipedalism-s || Speech requires voluntary breath control, which can evolve after bipedalism frees breathing from the constraint posed by the mechanics of locomotion.
 +
|---
 +
| Reassurance || Speech provides a means for females to reassure their offspring who have to be put down while foraging.
 +
|---
 +
| Sociality || Social pressure for more elaborate communication triggers evolution of speech.
 +
|---
 +
| Hunting || Collective hunting requires a means of effective communication and therefore triggers evolution of speech.
 +
|---
 +
| Culture || Transmitting cultural tradition (e.g., how to cope with unusually severe droughts) from one generation to the next requires a means of effective communication and therefore triggers evolution of speech.
 +
|---
 +
|colspan="2"| '''Other traits that could be explained by an aquatic phase in human evolution
 +
|---
 +
| Baby swimming || Human babies can be taken for a swim long before they can walk. They are comfortable in water and capable of holding their breath when submerged.
 +
|---
 +
| Nose || Unlike apes, humans have an arched nose and flexible nostrils. These help prevent water from entering the respiratory tract when diving.
 +
|---
 +
| Smell || Humans have a relatively weak sense of smell, as aquatic mammals often do.
 +
|---
 +
| Webbing || Humans have partial webbing between their fingers and toes. Webbed feet are common among semi-aquatic animals (such as otters and ducks), but are not found in non-human primates.
 +
|---
 +
| Eccrine glands || Cooling sweat is excreted from eccrine glands in humans but from apocrine glands in other primates. Apocrine glands could have lost their thermoregulatory function in human ancestors during a period when dip-cooling replaced sweat-cooling.
 +
|---
 +
| Sweating || Humans sweat more profusely than any other primate. Since this can lead to fatal loss of water and electrolytes in a few hours, the trait probably evolved in conditions of abundant water and salt supply.
 +
|---
 +
| Diving-o || Compared to other primates, humans are stronger swimmers and can dive both deeper and further.
 +
|---
 +
| Apnea || The diving reflex (slowing down of heartbeat and oxygen usage in water) increases the resistance of the brain to apnea, and its magnitude in human divers is comparable to that in semi-aquatic mammals such as otters and beavers.
 +
|---
 +
| Fond of water || Compared to other primates, humans are unusually fond of immersing themselves in water. This is manifested in the popularity of beach holidays, swimming and bathing.
 +
|}
  
 
The answerers' opinions should be used as continuous [0,1] variables in such a way that each answer is transformed into its quantile of all answers to that question. Then neural networks, Bayesian belief network analyzers (such as B-source), or other statistical tools can be applied.
 
The answerers' opinions should be used as continuous [0,1] variables in such a way that each answer is transformed into its quantile of all answers to that question. Then neural networks, Bayesian belief network analyzers (such as B-source), or other statistical tools can be applied.
  
 
For single answer analyses, multinomial regression models should be applied.
 
For single answer analyses, multinomial regression models should be applied.
 +
 +
In the following sections, we will present results about support to different hypotheses explaining the traits studied. We have two sources of information and three graphs for each hypothesis: Survey to authors of relevant journals, with ca. 1200 responses; and authors of articles about human evolution and the traits of interest (272 individual authors). The survey graphs on the left show the repondents' views on how likely each hypothesis is. The middle graphs show the same information separated by the expertise of the respondent (and for visibility, we assumed the X axis to be continous so that we could draw probability densities). The graphs on the right show the support from article authors in the literature review. Each hypothesis has one row of graphs, and they are ordered by the trait the hypotheses explain.
 +
 +
==== Bipedalism ====
 +
 +
{| class="wikitable collapsible collapsed"
 +
! Show details
 +
|----
 +
| [[File:human_energy_efficiency_survey.png|400px]] || [[File:human_energy_efficiency_expertise.png|400px]] || [[File:human_energy_efficiency_author.png|400px]]
 +
|---
 +
| [[File:human_thinner_branches_survey.png|400px]] || [[File:human_thinner_branches_expertise.png|400px]] || [[File:human_thinner_branches_author.png|400px]]
 +
|---
 +
| [[File:human_wading_survey.png|400px]] || [[File:human_wading_expertise.png|400px]] || [[File:human_wading_author.png|400px]]
 +
|---
 +
| [[File:human_thermoregulation-b_survey.png|400px]] || [[File:human_thermoregulation-b_expertise.png|400px]] || [[File:human_thermoregulation-b_author.png|400px]]
 +
|---
 +
| [[File:human_better_view_survey.png|400px]] || [[File:human_better_view_expertise.png|400px]] || [[File:human_better_view_author.png|400px]]
 +
|---
 +
| [[File:human_foraging_survey.png|400px]] || [[File:human_foraging_expertise.png|400px]] || [[File:human_foraging_author.png|400px]]
 +
|---
 +
| [[File:human_carrying_food_survey.png|400px]] || [[File:human_carrying_food_expertise.png|400px]] || [[File:human_carrying_food_author.png|400px]]
 +
|---
 +
| [[File:human_carrying_baby_survey.png|400px]] || [[File:human_carrying_baby_expertise.png|400px]] || [[File:human_carrying_baby_author.png|400px]]
 +
|---
 +
| [[File:human_tool_use_survey.png|400px]] || [[File:human_tool_use_expertise.png|400px]] || [[File:human_tool_use_author.png|400px]]
 +
|---
 +
| [[File:human_genitals_survey.png|400px]] || [[File:human_genitals_expertise.png|400px]] ||
 +
|---
 +
|}
 +
 +
==== Brain ====
 +
 +
{| class="wikitable collapsible collapsed"
 +
! Show details
 +
|---
 +
| [[File:human_meat_survey.png|400px]] || [[File:human_meat_expertise.png|400px]] || [[File:human_meat_author.png|400px]]
 +
|---
 +
| [[File:human_fish_survey.png|400px]] || [[File:human_fish_expertise.png|400px]] || [[File:human_fish_author.png|400px]]
 +
|---
 +
| [[File:human_cooking_survey.png|400px]] || [[File:human_cooking_expertise.png|400px]] || [[File:human_cooking_author.png|400px]]
 +
|---
 +
| [[File:human_social_survey.png|400px]] || [[File:human_social_expertise.png|400px]] || [[File:human_social_author.png|400px]]
 +
|---
 +
| [[File:human_collaborative_hunting_survey.png|400px]] || [[File:human_collaborative_hunting_expertise.png|400px]] || [[File:human_collaborative_hunting_author.png|400px]]
 +
|---
 +
| [[File:human_language_survey.png|400px]] || [[File:human_language_expertise.png|400px]] || [[File:human_language_author.png|400px]]
 +
|---
 +
| [[File:human_warfare_survey.png|400px]] || [[File:human_warfare_expertise.png|400px]] || [[File:human_warfare_author.png|400px]]
 +
|---
 +
| [[File:human_neoteny_survey.png|400px]] || [[File:human_neoteny_expertise.png|400px]] || [[File:human_neoteny_author.png|400px]]
 +
|---
 +
| [[File:human_bipedalism-b_survey.png|400px]] || [[File:human_bipedalism-b_expertise.png|400px]] ||
 +
|---
 +
| [[File:human_nakedness_survey.png|400px]] || [[File:human_nakedness_expertise.png|400px]] || [[File:human_nakedness_author.png|400px]]
 +
|---
 +
|}
 +
 +
==== Nakedness ====
 +
 +
{| class="wikitable collapsible collapsed"
 +
! Show details
 +
|---
 +
| [[File:human_skin_contact_baby_survey.png|400px]] || [[File:human_skin_contact_baby_expertise.png|400px]] || [[File:human_skin_contact_baby_author.png|400px]]
 +
|---
 +
| [[File:human_skin_contact_sex_survey.png|400px]] || [[File:human_skin_contact_sex_expertise.png|400px]] || [[File:human_skin_contact_sex_author.png|400px]]
 +
|---
 +
| [[File:human_cleanliness_survey.png|400px]] || [[File:human_cleanliness_expertise.png|400px]] ||
 +
|---
 +
| [[File:human_ectoparasites_survey.png|400px]] || [[File:human_ectoparasites_expertise.png|400px]] || [[File:human_ectoparasites_author.png|400px]]
 +
|---
 +
| [[File:human_drag_survey.png|400px]] || [[File:human_drag_expertise.png|400px]] || [[File:human_drag_author.png|400px]]
 +
|---
 +
| [[File:human_thermoregulation-h_survey.png|400px]] || [[File:human_thermoregulation-h_expertise.png|400px]] || [[File:human_thermoregulation-h_author.png|400px]]
 +
|---
 +
| [[File:human_large_mammal_survey.png|400px]] || [[File:human_large_mammal_expertise.png|400px]] ||
 +
|---
 +
| [[File:human_clothes_survey.png|400px]] || [[File:human_clothes_expertise.png|400px]] || [[File:human_clothes_author.png|400px]]
 +
|---
 +
|}
 +
 +
==== Subcutaneous fat ====
 +
 +
{| class="wikitable collapsible collapsed"
 +
! Show details
 +
|---
 +
| [[File:human_energy_supply_survey.png|400px]] || [[File:human_energy_supply_expertise.png|400px]] || [[File:human_energy_supply_author.png|400px]]
 +
|---
 +
| [[File:human_insulation_survey.png|400px]] || [[File:human_insulation_expertise.png|400px]] || [[File:human_insulation_author.png|400px]]
 +
|---
 +
| [[File:human_savannah_thermoregulation_survey.png|400px]] || [[File:human_savannah_thermoregulation_expertise.png|400px]] || [[File:human_savannnah_thermoregulation_author.png|400px]]
 +
|---
 +
| [[File:human_body_shape_survey.png|400px]] || [[File:human_body_shape_expertise.png|400px]] || [[File:human_body_shape_author.png|400px]]
 +
|---
 +
|}
 +
 +
==== Larynx ====
 +
 +
{| class="wikitable collapsible collapsed"
 +
! Show details
 +
|---
 +
| [[File:human_articulation_survey.png|400px]] || [[File:human_articulation_expertise.png|400px]] || [[File:human_articulation_author.png|400px]]
 +
|---
 +
| [[File:human_impressive_voice_survey.png|400px]] || [[File:human_impressive_voice_expertise.png|400px]] || [[File:human_impressive_voice_author.png|400px]]
 +
|---
 +
| [[File:human_diving-l_survey.png|400px]] || [[File:human_diving-l_expertise.png|400px]] ||
 +
|---
 +
|}
 +
 +
==== Speech ====
 +
 +
{| class="wikitable collapsible collapsed"
 +
! Show details
 +
|---
 +
| [[File:human_larynx_survey.png|400px]] || [[File:human_larynx_expertise.png|400px]] || [[File:human_larynx_author.png|400px]]
 +
|---
 +
| [[File:human_diving-s_survey.png|400px]] || [[File:human_diving-s_expertise.png|400px]] || [[File:human_diving-s_author.png|400px]]
 +
|---
 +
| [[File:human_bipedalism-s_survey.png|400px]] || [[File:human_bipedalism-s_expertise.png|400px]] || [[File:human_bipedalism-s_author.png|400px]]
 +
|---
 +
| [[File:human_reassurance_survey.png|400px]] || [[File:human_reassurance_expertise.png|400px]] || [[File:human_reassurance_author.png|400px]]
 +
|---
 +
| [[File:human_sociality_survey.png|400px]] || [[File:human_sociality_expertise.png|400px]] || [[File:human_sociality_author.png|400px]]
 +
|---
 +
| [[File:human_hunting_survey.png|400px]] || [[File:human_hunting_expertise.png|400px]] || [[File:human_hunting_author.png|400px]]
 +
|---
 +
| [[File:human_culture_survey.png|400px]] || [[File:human_culture_expertise.png|400px]] || [[File:human_culture_author.png|400px]]
 +
|---
 +
|}
 +
 +
==== Other traits ====
 +
 +
{| class="wikitable collapsible collapsed"
 +
|+'''Other traits that could be explained by a waterside hypothesis
 +
! Show details
 +
|---
 +
| [[File:human_baby_swimming_survey.png|400px]] || [[File:human_baby_swimming_expertise.png|400px]] ||
 +
|---
 +
| [[File:human_nose_survey.png|400px]] || [[File:human_nose_expertise.png|400px]] || [[File:human_nose_author.png|400px]]
 +
|---
 +
| [[File:human_smell_survey.png|400px]] || [[File:human_smell_expertise.png|400px]] || [[File:human_smell_author.png|400px]]
 +
|---
 +
| [[File:human_webbing_survey.png|400px]] || [[File:human_webbing_expertise.png|400px]] ||
 +
|---
 +
| [[File:human_eccrine_glands_survey.png|400px]] || [[File:human_eccrine_glands_expertise.png|400px]] ||
 +
|---
 +
| [[File:human_sweating_survey.png|400px]] || [[File:human_sweating_expertise.png|400px]] || [[File:human_sweating_author.png|400px]]
 +
|---
 +
| [[File:human_diving-o_survey.png|400px]] || [[File:human_diving-o_expertise.png|400px]] || [[File:human_diving-o_author.png|400px]]
 +
|---
 +
| [[File:human_apnea_survey.png|400px]] || [[File:human_apnea_expertise.png|400px]] ||
 +
|---
 +
|[[File:human_fond_of_water_survey.png|400px]] || [[File:human_fond_of_water_expertise.png|400px]] ||
 +
|}
 +
 +
===Survey===
  
 
[[File:human_evoluion_survey_correlations.png|800px]]
 
[[File:human_evoluion_survey_correlations.png|800px]]
  
−
Correlations in the answers in the survey data between different hypotheses.
+
The graph above shows the results for correlations done from the survey answers between all different hypotheses. In most cases the correlations were quite small, and almost always positive. There are only a few negative correlations in these answers, and in them the correlations are very small, -0.14 being the strongest negative correlation. The most notable correlations are between the hypotheses that suggest a semi-aquatic ancestor. If one believes in one, then all the water-relates hypotheses seem likely, and if one doesn't, they seem unlikely. Interestingly, eating of fish and other sea food enabling brain growth does not correlate with the rest of the water-related hypotheses, even though if fish was needed for brain growth, it indicades humans lived on shores, fishing and wading, thus probably spending a significant time in water, which is also the basis for all the other waterside hypotheses. The fish hypothesis does however have a correlation with eating meat being a major step toward bigger brains, as well as cooking the food, which makes it possible to get more energy from it.
 +
 
 +
The graph below shows the results for principal components analysis done on the survey data. All the water-related hypotheses (except eating fish) are at the top right corner, and the rest are at the bottom. This means those people who have an opinion about one water-related hypothesis are more or less the same opinion about the rest of them. What people thought about the water-related hypotheses doesn't seem to have much of a connection to their opinions about the rest of the hypotheses.
 +
 
 +
For other hypotheses it seems that the idea that brain developed as a response to hairlessness convinces the same people as the hypotheses of hairlessness evolving to enhance skin contact and bipedalism to show off genitals. Completely different people were the people who found it convincing that the brain developed to enable speaking or hunting and that the subcutaneous fat layer developed as an energy supply.
 +
 
 +
The sizes for the dots tell about how likely the hypothesis was found to explain the trait in the survey. The bigger the dot, the more likely people thought it was. The numbers from the scaling were gotten by calculating the average answer (1 being very likely and 5 being very unlikely), and subtracting that from 5 (to get the likeliest ones with the highest values instead of the lowest).
 +
 
 +
[[File:human_evolution_poca.png|700px]]
 +
 
 +
===Literary review===
 +
 
 +
Hidden below you can find a summary of the articles found in a literary review on the evolution of human traits done in the summer 2016 to find out, which hypothesis on which human traits are currently discussed in scientific articles, and which according to them seem the most likely ways the human traits have evolved. F, A and N in the last column stand for For, Against and Neutral, according to which point of view is argued in the article about the hypothesis in question.
 +
 
 +
{{hidden|1=
 +
 
 +
<t2b name="Literary review summary" index="Article,Year,Type,Hypothesis,Trait" obs="For Against Neutral" unit="-">
 +
Ko 2015-1|2015|Review article|Better view|Bipedalism|A
 +
Videan & McGrew 2002|2002|Research article|Better view|Bipedalism|A
 +
Bender et al. 2007|2007|Review article|Better view|Bipedalism|A
 +
Sutou 2012|2012|Essay|Carrying baby|Bipedalism|F
 +
Watson et al. 2008|2008|Research article|Carrying baby|Bipedalism|A
 +
David-Barret & Dunbar 2016|2016|Research article|Carrying food|Bipedalism|A
 +
Ko 2015-1|2015|Review article|Carrying food|Bipedalism|F
 +
Videan & McGrew 2002|2002|Research article|Carrying food|Bipedalism|F
 +
Carvalho et al. 2012|2012|Comment|Carrying food|Bipedalism|F
 +
Sutou 2012|2012|Essay|Carrying food|Bipedalism|F
 +
Lieberman 2011|2011|Essay|Energy efficiency|Bipedalism|F
 +
Rodman & McHenry 1980|1980|Research article|Energy efficiency|Bipedalism|F
 +
David-Barret & Dunbar 2016|2016|Research article|Energy efficiency|Bipedalism|N
 +
Sockol et al. 2007|2007|Research article|Energy efficiency|Bipedalism|F
 +
Leonard & Robertson 1995|1995|Comment|Energy efficiency|Bipedalism|F
 +
Leonard & Robertson 2001|2001|Comment|Energy efficiency|Bipedalism|F
 +
Isbell & Young 1996|1996|Review article|Energy efficiency|Bipedalism|F
 +
Pontzer et al. 2009|2009|Research article|Energy efficiency|Bipedalism|F
 +
Pickford 2002|2002|Review article|Energy efficiency|Bipedalism|F
 +
Halsey & White 2012|2012|Research article|Energy efficiency|Bipedalism|A
 +
Wang et al. 2003|2003|Research article|Energy efficiency|Bipedalism|A
 +
Steudel 1996|1996|Research article|Energy efficiency|Bipedalism|A
 +
Taylor & Rowntree 1973|1973|Comment|Energy efficiency|Bipedalism|A
 +
Steudel-Numbers 2003|2003|Research article|Energy efficiency|Bipedalism|A
 +
Crompton et al. 1998|1998|Research article|Energy efficiency|Bipedalism|A
 +
Wheeler 1984|1984|Review article|Energy efficiency|Bipedalism|N
 +
Carey & Crompton 2005|2005|Research article|Energy efficiency|Bipedalism|N
 +
Videan & McGrew 2002|2002|Research article|Foraging|Bipedalism|F
 +
David-Barret & Dunbar 2016|2016|Research article|Thermoregulation-b|Bipedalism|N
 +
Wheeler 1984|1984|Review article|Thermoregulation-b|Bipedalism|F
 +
Morgan 1993|1993|Review article|Thermoregulation-b|Bipedalism|A
 +
Porter 1993|1993|Comment|Thermoregulation-b|Bipedalism|F
 +
Wheeler 1994|1994|Comment|Thermoregulation-b|Bipedalism|F
 +
Wheeler 1991-1|1991|Research article|Thermoregulation-b|Bipedalism|F
 +
Wheeler 1991-2|1991|Research article|Thermoregulation-b|Bipedalism|F
 +
Ruxton & Wilkinson 2011|2011|Research article|Thermoregulation-b|Bipedalism|A
 +
Ko 2015-1|2015|Review article|Thermoregulation-b|Bipedalism|A
 +
Chaplin et al. 1994|1994|Research article|Thermoregulation-b|Bipedalism|A
 +
Bender et al. 2007|2007|Review article|Thermoregulation-b|Bipedalism|A
 +
Roberts & Thorpe  2014|2014|Review article|Thinner branches|Bipedalism|F
 +
Stanford 2006|2006|Research article|Thinner branches|Bipedalism|F
 +
Crompton et al. 2010|2010|Review article|Thinner branches|Bipedalism|F
 +
Sigmon 1971|1971|Research article|Thinner branches|Bipedalism|F
 +
Stanford 2002|2002|Brief communication|Thinner branches|Bipedalism|F
 +
Senut 2006|2006|Book section|Thinner branches|Bipedalism|F
 +
Thorpe 2009|2009|Research article|Thinner branches|Bipedalism|F
 +
Tuttle 1981|1981||Thinner branches|Bipedalism|F
 +
Preuschoft 2004|2004|Review article|Thinner branches|Bipedalism|F
 +
Thorpe et al. 2007-1|2007|Report|Thinner branches|Bipedalism|F
 +
Thorpe et al. 2014|2014|Debate|Thinner branches|Bipedalism|F
 +
Crompton et al. 2003|2003||Thinner branches|Bipedalism|F
 +
Gebo 1996|1996|Research article|Thinner branches|Bipedalism|A
 +
Begun et al. 2007|2007|Comment|Thinner branches|Bipedalism|A
 +
Thorpe et al. 2007-2|2007|Comment|Thinner branches|Bipedalism|F
 +
Wheeler 1984|1984|Review article|Tool use|Bipedalism|A
 +
Harcourt‐Smith 2007|2007|Book section|Tool use|Bipedalism|A
 +
Bender et al. 1997|1997||Wading|Bipedalism|F
 +
Morgan 1993|1993|Review article|Wading|Bipedalism|F
 +
Wrangham et al. 2009|2009|Research article|Wading|Bipedalism|F
 +
Niemitz 2010|2010|Review article|Wading|Bipedalism|F
 +
Kuliukas 2002|2002|Research article|Wading|Bipedalism|F
 +
Kuliukas 2009|2009|Review article|Wading|Bipedalism|F
 +
Kuliukas et al. 2009|2009|Research article|Wading|Bipedalism|F
 +
Bender et al. 2007|2007|Review article|Wading|Bipedalism|F
 +
Isler & van Schaik 2014|2014|Review article|Collaborative hunting|Brain|F
 +
Carmody & Wrangham 2009|2009|Research article|Cooking|Brain|N
 +
Joordens et al. 2014|2014|Research article|Fish|Brain|F
 +
Broadhurst et al. 2002|2002|Review article|Fish|Brain|F
 +
Broadhurst et al. 1998|1998|Review article|Fish|Brain|F
 +
Cunnane 2007|2007|Comment|Fish|Brain|F
 +
Cunnane et al. 2007|2007|Short report|Fish|Brain|F
 +
Cunnane & Crawford 2003|2003|Review article|Fish|Brain|F
 +
Cunnane et al. 1993|1993|Research article|Fish|Brain|F
 +
Cunnane & Crawford 2014|2014|Research article|Fish|Brain|F
 +
Verhaegen 1995|1995|Brief communication|Fish|Brain|F
 +
Braun et al. 2010|2010|Research article|Fish|Brain|F
 +
Carlson & Kingston 2007-1|2007|Research article|Fish|Brain|A
 +
Carlson & Kingston 2007-2|2007|Comment|Fish|Brain|A
 +
Langdon 2006|2006|Review article|Fish|Brain|A
 +
Lakatos & Janka 2008|2008||Language|Brain|F
 +
Brown & Greenhood 1991|1991|Review article|Language|Brain|F
 +
Falk 1980|1980|Review article|Language|Brain|F
 +
Previc 2002|2002|Brief communication|Meat|Brain|F
 +
Speth 1989|1989|Research article|Meat|Brain|A
 +
Ibraimov 2007|2007|Review article|Nakedness|Brain|N
 +
Shea 1989|1989|Review article|Neoteny|Brain|A
 +
Sandel et al. 2016|2016|Research article|Social|Brain|F
 +
Shultz & Dunbar 2010|2010|Research article|Social|Brain|F
 +
Shultz & Dunbar 2007|2007|Review article|Social|Brain|F
 +
Navarrete et al. 2011|2011|Letter|Social|Brain|F
 +
Dunbar 1992|1992|Research article|Social|Brain|F
 +
Dunbar 1998|1998|Research article|Social|Brain|F
 +
Dunbar 2003|2003|Review article|Social|Brain|F
 +
Allman 1999|1999|Book section|Social|Brain|A
 +
Falk 1980|1980|Review article|Warfare|Brain|A
 +
Pitt 1978|1978|Review article|Warfare|Brain|F
 +
Pawlowski 1999|1999||Body shape|Fat|N
 +
Cunnane & Crawford 2003|2003|Review article|Energy supply|Fat|F
 +
Wells 2006|2006|Research article|Energy supply|Fat|F
 +
Correia et al. 2004|2004|Research article|Energy supply|Fat|F
 +
Rebora 2010|2010|Review article|Insulation|Fat|A
 +
Wheeler 1984|1984|Review article|Savannah thermoregulation|Fat|F
 +
Pawlowski 1998|1998||Savannah thermoregulation|Fat|F
 +
Pawlowski 1999|1999||Savannah thermoregulation|Fat|F
 +
Rantala 2007|2007|Review article|Clothes|Hairlessness|A
 +
Pagel & Bomder 2003|2003|Letter|Clothes|Hairlessness|N
 +
Pagel & Bomder 2004|2004|Book section|Clothes|Hairlessness|N
 +
Rebora 2010|2010|Review article|Clothes|Hairlessness|A
 +
Kushlan 1985|1985|Review article|Clothes|Hairlessness|N
 +
Glass 1966|1966|Letter|Clothes|Hairlessness|F
 +
Hershkovitz 1966|1966|Letter|Clothes|Hairlessness|A
 +
Brace et al. 1966|1966|Letter|Clothes|Hairlessness|A
 +
Rantala 2007|2007|Review article|Drag|Hairlessness|A
 +
Pagel & Bomder 2003|2003|Letter|Drag|Hairlessness|A
 +
Rebora 2010|2010|Review article|Drag|Hairlessness|A
 +
Wheeler 1985|1985|Review article|Drag|Hairlessness|A
 +
Rantala 2007|2007|Review article|Ectoparasites|Hairlessness|F
 +
Pagel & Bomder 2003|2003|Letter|Ectoparasites|Hairlessness|F
 +
Rantala 1999|1999|Discussion|Ectoparasites|Hairlessness|F
 +
Dean & Siva-Jothy 2012|2012|Letter|Ectoparasites|Hairlessness|F
 +
Pagel & Bomder 2004|2004|Book section|Ectoparasites|Hairlessness|F
 +
Dunn 1966|1966|Comment|Ectoparasites|Hairlessness|A
 +
Rebora 2010|2010|Review article|Ectoparasites|Hairlessness|A
 +
Giles 2011|2011|Review article|Skin contact baby|Hairlessness|F
 +
Giles 2011|2011|Review article|Skin contact sex|Hairlessness|F
 +
Rantala 2007|2007|Review article|Skin contact sex|Hairlessness|A
 +
Wheeler 1984|1984|Review article|Thermoregulation-h|Hairlessness|F
 +
Ruxton & Wilkinson 2011|2011|Research article|Thermoregulation-h|Hairlessness|F
 +
Ibraimov 2007|2007|Review article|Thermoregulation-h|Hairlessness|F
 +
Rantala 2007|2007|Review article|Thermoregulation-h|Hairlessness|A
 +
Pagel & Bomder 2003|2003|Letter|Thermoregulation-h|Hairlessness|A
 +
Rebora 2010|2010|Review article|Thermoregulation-h|Hairlessness|A
 +
Wheeler 1985|1985|Review article|Thermoregulation-h|Hairlessness|F
 +
Schwarts & Rosenblum 2005|2005|Research article|Thermoregulation-h|Hairlessness|F
 +
Lupi 2008|2008|Review article|Thermoregulation-h|Hairlessness|F
 +
Wheeler 1996|1996|Comment|Thermoregulation-h|Hairlessness|F
 +
Wheeler 1992|1992|Research article|Thermoregulation-h|Hairlessness|F
 +
Ebling 1985|1985|Review article|Thermoregulation-h|Hairlessness|F
 +
Kushlan 1985|1985|Review article|Thermoregulation-h|Hairlessness|F
 +
Brace et al. 1966|1966|Letter|Thermoregulation-h|Hairlessness|F
 +
Amaral 1996|1966|Review article|Thermoregulation-h|Hairlessness|N
 +
Davidson 2003|2003|Review article|Articulation|Larynx|F
 +
Shprintzen 2003|2003|Comment|Articulation|Larynx|A
 +
Nishimura et al. 2006|2006|Research article|Articulation|Larynx|A
 +
Frey et al. 2011|2011||Impressive voice|Larynx|F
 +
Frey et al. 2015|2015|Research article|Impressive voice|Larynx|F
 +
Hombert 2010|2010|Book section|Impressive voice|Larynx|F
 +
Fitch & Reby 2001|2001|Research article|Impressive voice|Larynx|F
 +
Fitch 2002|2002|Review article|Impressive voice|Larynx|F
 +
Apicella & Feinberg 2009|2009|Research article|Impressive voice|Larynx|N
 +
Apicella et al. 2007|2007|Letter|Impressive voice|Larynx|N
 +
Falhman & Schagatey 2014|2014|Review article|Diving-o|Other|F
 +
Schagatey 2011|2011|Book section|Diving-o|Other|F
 +
Verhaegen 1993|2013|Review article|Nose|Other|F
 +
Mladina et al. 2009|2009|Review article|Nose|Other|N
 +
Verhaegen 1995|1995|Brief communication|Smell|Other|F
 +
Verhaegen et al. 2007|2007|Book section|Smell|Other|F
 +
Wheeler 1991-2|1991|Research article|Sweating|Other|A
 +
Wheeler 1992|1992|Research article|Sweating|Other|A
 +
MacLarnon & Hewitt 1999|1999|Research article|Bipedalism-s|Speech|A
 +
Stout & Chaminade 2012|2012|Review article|Culture|Speech|F
 +
Corballis 2009|2009|Book section|Culture|Speech|F
 +
Verhaegen 1995|1995|Brief communication|Diving-s|Speech|F
 +
Verhaegen et al. 2002|2002|Opinion|Diving-s|Speech|F
 +
MacLarnon & Hewitt 1999|1999|Research article|Diving-s|Speech|A
 +
Lieberman 1973|1973|Review article|Hunting|Speech|N
 +
Shprintzen 2003|2003|Comment|Larynx|Speech|A
 +
Nishimura et al. 2006|2006|Research article|Larynx|Speech|A
 +
Falk 2004|2004|Review article|Reassurance|Speech|F
 +
Brown & Greenhood 1991|1991|Review article|Sociality|Speech|F
 +
Dunbar 1993|1993||Sociality|Speech|F
 +
Hamilton 1974|1974|Review article|Sociality|Speech|F
 +
Kurland & Beckerman 1985|1985||Sociality|Speech|F
 +
Locke 2001|2001|Review article|Sociality|Speech|F
 +
Ko 2015-2|2015|Review article|Sociality|Speech|N
 +
</t2b>
 +
 
 +
}}
  
−
[[File:Graph of human trait evolution hypotheses.png|400px]]
+
There are may histograms drawn from the review data to show how many of the found articles support or argue against all of the different hypotheses. They also show which hypotheses are the most talked about in the literature. Another set of histograms were drawn from the amount of authors writing the articles about each of the hypotheses. For this, all the authors for all articles were listed and plotted the same way as he articles, being for, against or writing something neural about the hypothesis. Before drawing the histograms the data was processed so that one author was counted only once to support or oppose a certain hypothesis, even if they had authored more than one article on the topic. You can see the histograms by trait from the authors below. Green color means supporting, red opposing and blue writing something neutral about the topic. All of the histograms can be found [http://en.opasnet.org/en-opwiki/index.php?title=Special:RTools&id=SzNHyHUMgpeJgNnn here] and [http://en.opasnet.org/en-opwiki/index.php?title=Special:RTools&id=gGXQ8bD1mlQe1QJD here]. Note that not all of the hypotheses in the survey were discussed at all in any of the articles in the literature review.
  
−
The relations between writers and hypotheses. How the different writers wrote about hypotheses. Green lines means supporting, red lines mean arguing against, and grey lines means writing something on the topic, but not being clearly for or against the hypothesis.
+
[[File:human_evolution_authors_all.png|700px]]
 +
 
 +
[[File:Graph of human trait evolution hypotheses.png|600px]]
 +
 
 +
The lower graph above shows relations between writers (small dots) and hypotheses (bubbles), or how the different writers wrote about hypotheses. Green lines mean supporting, red lines mean arguing against, and grey lines mean writing something on the topic, but not being clearly for or against the hypothesis. It shows us which hypotheses are discussed by the same authors, and whether the author supported both, opposed both, or whether they're hypotheses that one person doesn't think likely to both be true.
 +
 
 +
Several observations can be made from the graph. First, most authors only discussed a single hypothesis. The maximum number of different hypothesis discussed by a single author was six {{comment|# |CHECK THE DATA|--[[User:Jouni|Jouni]] ([[User talk:Jouni|talk]]) 12:48, 4 September 2016 (UTC)}}, but few authors discussed more than two hypotheses.
 +
 
 +
Second, some areas, notably nakedness, stimulated many authors to discuss several possible hypotheses. Another similar area was bipedalism, where, interestingly, authors supporting thinner branch hypothesis simultaneously opposed energy efficiency hypothesis. However, in the survey data these two hypotheses were not correlated.
 +
 
 +
Third, there are some isolated hypotheses such as neoteny, culture, and impressive voice, where the authors of these topics did not discuss any of the other hypotheses, and also none of the other authors discussed these hypotheses.
 +
 
 +
It can be concluded that there is no single study that would systematically look at the evolution of important human traits and evaluate strengths and weaknesses of related hypotheses.
 +
 
 +
=== Student survey ===
 +
 
 +
[[File:Bipedalism student survey.png|300px|thumb|Hypotheses and reasonings related to bipedalism.]]A questionnaire was sent to students to study whether they found the reasoning of each hypothesis convincing.
 +
 
 +
{{hidden|
 +
<t2b name="Student survey" index="Trait,Hypothesis,Reasoning" obs="For Against Neutral" unit="-">
 +
Bipedalism|Better view|You see further when on two legs|F
 +
Bipedalism|Carrying items|Chimps carry food in hands|F
 +
Bipedalism|Carrying items|Females prefer males that can carry food|F
 +
Bipedalism|Carrying items|Hairless mothers had to carry babies|F
 +
Bipedalism|Carrying items|Carrying baby on either side uses energy|A
 +
Bipedalism|Carrying items|First tools date 1.5 M years after bipedalism|A
 +
Bipedalism|Energy efficiency|Knuckle walk is least energy efficient|F
 +
Bipedalism|Energy efficiency|Bipedalism is at least as efficient as tetrapedalism|F
 +
Bipedalism|Energy efficiency|Easy to develop efficient bipedalism|F
 +
Bipedalism|Energy efficiency|For chimps bipedalism is less efficient than on knuckles|A
 +
Bipedalism|Energy efficiency|Bipedalism is not more efficient than tetrapedalism|A
 +
Bipedalism|Energy efficiency|Knees-bent bipedalism is not efficient|A
 +
Bipedalism|Foraging|Current primates walk on two legs when eating from bushes|F
 +
Bipedalism|Foraging|First apes have structures for forging but not for long-distance walk|F
 +
Bipedalism|Foraging|On two legs you can reach higher|F
 +
Bipedalism|Foraging|During foraging, bipedalism is efficient|F
 +
Bipedalism|Foraging|There was no reason to focus on standing-height foods|A
 +
Bipedalism|Thermoregulation-b|Smaller surface area|F
 +
Bipedalism|Thermoregulation-b|Longer operation times on savannah|F
 +
Bipedalism|Thermoregulation-b|No other savannah animals are bipedalists|A
 +
Bipedalism|Thermoregulation-b|There are easier ways to thermoregulate|A
 +
Bipedalism|Thermoregulation-b|Humans did not actually develop on savannah|A
 +
Bipedalism|Thinner branches|This is how orangutangs walk|F
 +
Bipedalism|Thinner branches|Chimps cannot extend their legs like humans and orangutangs|F
 +
Bipedalism|Thinner branches|Human scapula resembles that of orangutangs|F
 +
Bipedalism|Thinner branches|Chimp climbing is like bipedalism|F
 +
Bipedalism|Thinner branches|Many attachment points help moving on thinner branches|F
 +
Bipedalism|Thinner branches|First erect humans had thumb-like pollux|F
 +
Bipedalism|Thinner branches|Wrist bone association with knuckle walk is false|F
 +
Bipedalism|Thinner branches|If gorilla and chimp ancestors walk on knuckles, so did human ancestors|A
 +
Bipedalism|Thinner branches|Orangutangs are poor walkers on two legs.|A
 +
Bipedalism|Thinner branches|If human-oranguntang ancestors walked on trees, that should be seen in chimps and gorillas|A
 +
Bipedalism|Tools use|Bipedalism helps carrying tools around|F
 +
Bipedalism|Wading|Apes walk on two legs when wading|F
 +
Bipedalism|Wading|Two other primate species waded|F
 +
Bipedalism|Wading|Shallow waters offer a lot of food|F
 +
Bipedalism|Wading|Boyance helps bipedalism|F
 +
Bipedalism|Wading|Bipedalism makes body streamlined for swimming|F
 +
Bipedalism|Wading|Primates usually don't go to water|A
 +
Bipedalism|Wading|From trees to ground is more parsimonious than trees-water-ground|A
 +
</t2b>
 +
}}
 +
 
 +
<rcode graphics=1>
 +
library(OpasnetUtils)
 +
library(ggplot2)
 +
library(igraph)
 +
dat <- opbase.data("Op_en5865",subset="Student survey")
 +
 
 +
#order <- c("F", "N", "A")
 +
 
 +
#dat$Result <- factor(dat$Result, levels=order)
 +
 
 +
for(i in 1:ncol(dat)) {dat[[i]] <- as.character(dat[[i]])}
 +
 
 +
edg <- data.frame(
 +
  from = c(dat$Reasoning, dat$Trait),
 +
  to = rep(dat$Hypothesis, 2),
 +
  Etype = c(rep("If then", nrow(dat)), rep("Makes relevant", nrow(dat))),
 +
  FAN = c(dat$Result, rep("", nrow(dat)))
 +
)
 +
edg <- edg[!duplicated(paste(edg$from, edg$to)) , ]
 +
 
 +
ver <- data.frame(
 +
    name = c(dat$Reasoning, dat$Trait, dat$Hypothesis),
 +
    Vtype = rep(c("Reasoning", "Trait", "Hypothesis"), each = nrow(dat))
 +
)
 +
 
 +
ver <- ver[!duplicated(ver$name) , ]
 +
 
 +
dag <- graph.data.frame(edg, directed = TRUE, vertices = ver)
 +
 
 +
colo <- c("Red", "Blue", "Pink", "Orange", "Brown", "Yellow", "Purple")
 +
 
 +
plot(
 +
  dag,
 +
  vertex.label.cex = 0.8,
 +
  vertex.size = ifelse(V(dag)$Vtype == "Hypothesis", 6, 3),
 +
  vertex.label.family = "Helvetica",
 +
  vertex.color = ifelse(V(dag)$Vtype == "Hypothesis",
 +
                        colo[as.factor(V(dag)$Trait)],
 +
                        "SkyBlue2"
 +
  ),
 +
  vertex.label = V(dag)$name, #ifelse(V(dag)$Vtype == "Hypothesis", V(dag)$name, NA),
 +
  edge.color = c("Gray", "Red", "Green")[as.factor(E(dag)$FAN)],
 +
  edge.arrow.size = 0.3,
 +
  layout = layout.fruchterman.reingold,
 +
  asp = 0.7
 +
)
 +
 
 +
</rcode>
  
 
=== Calculations ===
 
=== Calculations ===
Line 213: Line 800:
 
==== Histograms ====
 
==== Histograms ====
  
−
'''A code for drawing histograms from the literary review data showing the number of articles supporting and arguing against different hypotheses.
+
'''A code for drawing histograms from the literary review data showing the number of articles and and authors supporting and arguing against different hypotheses.
 +
You can see all the histograms by clicking "Run code".
 +
* Model run [http://en.opasnet.org/en-opwiki/index.php?title=Special:RTools&id=fCPaFIASXqpRCjW5 13.9.2016]
  
 
<rcode graphics="1">
 
<rcode graphics="1">
Line 222: Line 811:
 
authors <- opbase.data("Op_en5865",subset="Literary review authors")
 
authors <- opbase.data("Op_en5865",subset="Literary review authors")
  
−
#levels(summary_data$Article)
 
−
#levels(authors$Article)
 
−
 
−
#oprint(authors)
 
  
 
authors_summary <- merge(summary_data, authors,by="Article") # Merged tables
 
authors_summary <- merge(summary_data, authors,by="Article") # Merged tables
−
 
−
#oprint(authors_summary)
 
  
 
authors_short <- authors_summary[,c("Trait","Hypothesis","Result.x","Result.y")] # Irrelevant columns taken out
 
authors_short <- authors_summary[,c("Trait","Hypothesis","Result.x","Result.y")] # Irrelevant columns taken out
−
 
−
#oprint(authors_short)
 
  
 
authors_uniq <- unique(authors_short) # A list of authors only defending of attacking one hypothesis once.
 
authors_uniq <- unique(authors_short) # A list of authors only defending of attacking one hypothesis once.
−
 
−
#oprint(authors_uniq)
 
  
 
#ggplot(data=summary_data, aes(summary_data$Result)) + geom_histogram()
 
#ggplot(data=summary_data, aes(summary_data$Result)) + geom_histogram()
  
−
ggplot(summary_data, aes(Result, fill = Hypothesis)) + geom_histogram() # eri hypoteesit eri värillä
+
#ggplot(summary_data, aes(Result, fill = Hypothesis)) + geom_histogram() # eri hypoteesit eri värillä
  
−
ggplot(summary_data, aes(Hypothesis, fill = Result)) + geom_histogram() # F/A/N eri värillä hypoteeseittain.
+
#ggplot(summary_data, aes(Hypothesis, fill = Result)) + geom_histogram() # F/A/N eri värillä hypoteeseittain.
  
−
# Tässä lyhennetty koodia, koska 'data=' ei tarvita ja data.framen nimeä ei tarvita mainita aes:n sisällä vaan riittää sarakkeen nimi.
+
hypothesis.order <- c("Tool use","Foraging","Better view","Energy efficiency","Carrying baby","Carrying food","Thermoregulation-b","Wading","Thinner branches","Genitals","Social","Language","Collaborative hunting","Warfare","Meat","Neoteny","Fish","Cooking","Bipedalism-b","Nakedness","Thermoregulation-h","Ectoparasites","Large mammal","Clothes","Drag","Cleanliness","Skin contact sex","Skin contact baby","Energy supply","Savannah thermoregulation","Insulation","Body shape","Articulation","Impressive voice","Diving-l","Sociality","Hunting","Culture","Larynx","Bipedalism-s","Reassurance","Diving-s","Baby swimming","Sweating","Diving-o","Apnea","Nose","Fond of water","Smell","Webbing","Eccrine glands")
  
−
# Tästä eteenpäin bipedalismi hypoteeseja
+
authors_uniq$Hypothesis <- factor(authors_uniq$Hypothesis, levels=hypothesis.order)
  
−
#ggplot(summary_data[summary_data$Hypothesis == "Carrying baby",], aes(Result)) + geom_histogram(fill="blue") + labs(title="Carrying baby") + labs(x="", y="Count") + theme_grey(base_size=24)
 
  
−
#ggplot(summary_data[summary_data$Hypothesis == "Carrying food",], aes(Result)) + geom_histogram(fill="blue") + labs(title="Carrying food") + labs(x="", y="Count") + theme_grey(base_size=24)
+
## histograms per trait in articles
  
−
#ggplot(summary_data[summary_data$Hypothesis == "Energy efficiency",], aes(Result)) + geom_histogram(fill="blue") + labs(title="Energy efficiency") + labs(x="", y="Count") + theme_grey(base_size=24)
+
for(i in unique(summary_data$Trait)){
 +
trait2 <- ggplot(summary_data[summary_data$Trait == i,], aes(Hypothesis, fill = Result)) +
 +
geom_histogram() +
 +
labs(x="", y="Count", title= paste(i, "in articles")) +  
 +
theme_grey(base_size=24)
  
−
#ggplot(summary_data[summary_data$Hypothesis == "Thermoregulation-b",], aes(Result)) + geom_histogram(fill="blue") + labs(title="Thermoregulation") + labs(x="", y="Count") + theme_grey(base_size=24)
+
print(trait2)
  
−
#ggplot(summary_data[summary_data$Hypothesis == "Thinner branches",], aes(Result)) + geom_histogram(fill="blue") + labs(title="Thinner branches") + labs(x="", y="Count") + theme_grey(base_size=24)
+
}
  
−
biped <- ggplot(summary_data[summary_data$Trait == "Bipedalism",], aes(Result)) + geom_histogram(fill="blue") + labs(x="", y="Count") + labs(title="Bipedalism in articles") + theme_grey(base_size=24)
+
## histograms per trait by author
  
−
biped + facet_wrap(~Hypothesis, ncol=3)
+
for(i in unique(authors_uniq$Trait)){
 +
authors2 <- ggplot(authors_uniq[authors_uniq$Trait == i,], aes(Hypothesis, fill = Result.x)) +
 +
geom_histogram() +
 +
labs(x="", y="Count", title= paste(i, "by author")) +
 +
theme_grey(base_size=24)
  
−
biped_authors <- ggplot(authors_uniq[authors_uniq$Trait == "Bipedalism",], aes(Result.x)) + geom_histogram(fill="blue") + labs(x="", y="Count") + labs(title="Bipedalism by author") + theme_grey(base_size=24)
+
print(authors2)
  
−
biped_authors + facet_wrap(~Hypothesis, ncol=3)
+
}
  
−
ggplot(summary_data[summary_data$Trait == "Bipedalism",], aes(Hypothesis, fill = Result)) + geom_histogram() + labs(title="Bipedalism in articles") + labs(x="", y="Count") + theme_grey(base_size=24)
+
order <- c("F", "N", "A")
  
−
ggplot(authors_uniq[authors_uniq$Trait == "Bipedalism",], aes(Hypothesis, fill = Result.x)) + geom_histogram() + labs(title="Bipedalism by author") + labs(x="", y="Count") + theme_grey(base_size=24)
+
authors_uniq$Result.x <- factor(authors_uniq$Result.x, levels=order)
 +
summary_data$Result <- factor(summary_data$Result, levels=order)
  
−
#ggplot(summary_data[c((summary_data$Trait=="Bipedalism",),(summary_data$Year>1999,)], aes(Hypothesis, fill = Result)) + geom_histogram() + labs(title="Bipedalism by author") + labs(x="", y="Count") + theme_grey(base_size=24) # Ei toimi!
 
  
−
# Tästä eteenpäin aivohypoteeseja
+
## Histograms wrapped by trait in articles
  
−
#ggplot(summary_data[summary_data$Hypothesis == "Fish",], aes(Result)) + geom_histogram(fill="blue") + labs(title="Eating fish") + labs(x="", y="Count") + theme_grey(base_size=24)
+
for(i in unique(summary_data$Trait)) {
  
−
#ggplot(summary_data[summary_data$Hypothesis == "Social",], aes(Result)) + geom_histogram(fill="blue") + labs(title="Social brain") + labs(x="", y="Count") + theme_grey(base_size=24)
+
trait <- ggplot(summary_data[summary_data$Trait == i,], aes(Result)) +  
 +
geom_histogram(fill="blue") +
 +
labs(x = "", y = "count", title = paste(i, " in articles")) +
 +
theme_grey(base_size=24) +
 +
facet_wrap(~Hypothesis)
  
−
brain <- ggplot(summary_data[summary_data$Trait == "Brain",], aes(Result)) + geom_histogram(fill="blue") + labs(x="", y="Count") + labs(title="Brain in articles") + theme_grey(base_size=24)
+
print(trait)
 +
}
  
−
brain + facet_wrap(~Hypothesis, ncol=3)
 
  
−
brain_authors <- ggplot(authors_uniq[authors_uniq$Trait == "Brain",], aes(Result.x)) + geom_histogram(fill="blue") + labs(x="", y="Count") + labs(title="Brain by author") + theme_grey(base_size=24)
+
## Histograms wrapped by trait by authors
  
−
brain_authors + facet_wrap(~Hypothesis, ncol=3)
+
for(i in unique(authors_uniq$Trait)) {
 +
authors <- ggplot(authors_uniq[authors_uniq$Trait == i,], aes(Result.x)) +
 +
geom_histogram(fill="blue") +
 +
labs(x="", y="Count", title = paste(i, " by author")) +
 +
theme_grey(base_size=24) +
 +
facet_wrap(~Hypothesis)
  
−
ggplot(summary_data[summary_data$Trait == "Brain",], aes(Hypothesis, fill = Result)) + geom_histogram() + labs(title="Brain in articles") + labs(x="", y="Count") + theme_grey(base_size=24)
+
print(authors)
  
−
ggplot(authors_uniq[authors_uniq$Trait == "Brain",], aes(Hypothesis, fill = Result.x)) + geom_histogram() + labs(title="Brain by authors") + labs(x="", y="Count") + theme_grey(base_size=24)
+
}
  
−
# Tästä eteenpäin rasvahypoteeseja
 
  
−
fat <- ggplot(summary_data[summary_data$Trait == "Fat",], aes(Result)) + geom_histogram(fill="blue") + labs(x="", y="Count") + labs(title="Subcutaneous fat in articles") + theme_grey(base_size=24)
+
###Summary graphs
  
−
fat + facet_wrap(~Hypothesis, ncol=3)
+
authors_all <- ggplot(authors_uniq, aes (Hypothesis, fill = Result.x)) + geom_histogram() + labs(x="", y="count") + theme_grey(base_size=20) + theme(axis.text.x=element_text(angle=90,hjust=1,vjust=0.4))
  
−
fat_authors <- ggplot(authors_uniq[authors_uniq$Trait == "Fat",], aes(Result.x)) + geom_histogram(fill="blue") + labs(x="", y="Count") + labs(title="Subcutaneous fat by author") + theme_grey(base_size=24)
+
authors_all + facet_wrap(~Trait, ncol=4, scales="free_x")
  
−
fat_authors + facet_wrap(~Hypothesis, ncol=3)
+
#all <- ggplot(summary_data, aes(Hypothesis, fill=Result)) + geom_histogram() + labs(x="", y="count")
  
−
ggplot(summary_data[summary_data$Trait == "Fat",], aes(Hypothesis, fill = Result)) + geom_histogram() + labs(title="Subcutaneous fat in articles") + labs(x="", y="Count") + theme_grey(base_size=24)
+
#all + facet_wrap(~Trait, ncol=4, scales="free_x)
  
−
ggplot(authors_uniq[authors_uniq$Trait == "Fat",], aes(Hypothesis, fill = Result.x)) + geom_histogram() + labs(title="Subcutaneous fat by author") + labs(x="", y="Count") + theme_grey(base_size=24)
 
  
−
#Tästä eteenpäin karvattomuushypoteeseja
+
## All hypotheses separately
  
−
#ggplot(summary_data[summary_data$Hypothesis == "Clothes",], aes(Result)) + geom_histogram(fill="blue") + labs(title="Clothes") + labs(x="", y="Count") + theme_grey(base_size=24)
+
for(i in unique(authors_uniq$Hypothesis)) {
 +
authors_uniq$weight <- ifelse(authors_uniq$Hypothesis == i, 1, 0)
  
−
#ggplot(summary_data[summary_data$Hypothesis == "Ectoparasites",], aes(Result)) + geom_histogram(fill="blue") + labs(title="Ectoparasites") + labs(x="", y="Count") + theme_grey(base_size=24)
+
temp <- ggplot(authors_uniq, aes(x=Result.x, weight=weight)) +  
 +
geom_bar(fill="blue") +
 +
labs(x = "", y = "count", title = paste(i, " by authors")) +
 +
theme_grey(base_size=24) +
 +
coord_cartesian(ylim = c(0, 25))
  
−
#ggplot(summary_data[summary_data$Hypothesis == "Thermoregulation-h",], aes(Result)) + geom_histogram(fill="blue") + labs(title="Thermoregulation") + labs(x="", y="Count") + theme_grey(base_size=24)
+
print(temp)
−
 
+
}
−
hair <- ggplot(summary_data[summary_data$Trait == "Hairlessness",], aes(Result)) + geom_histogram(fill="blue") + labs(x="", y="Count") +  labs(title="Hairlessness in articles") + theme_grey(base_size=24)
 
−
 
 
−
hair + facet_wrap(~Hypothesis, ncol=3)
 
−
 
 
−
hair_authors <- ggplot(authors_uniq[authors_uniq$Trait == "Hairlessness",], aes(Result.x)) + geom_histogram(fill="blue") + labs(x="", y="Count") + labs(title="Hairlessness by author") + theme_grey(base_size=24)
 
−
 
 
−
hair_authors + facet_wrap(~Hypothesis, ncol=3)
 
−
 
 
−
ggplot(summary_data[summary_data$Trait == "Hairlessness",], aes(Hypothesis, fill = Result)) + geom_histogram() + labs(title="Hairlessness in articles") + labs(x="", y="Count") + theme_grey(base_size=24)
 
−
 
 
−
ggplot(authors_uniq[authors_uniq$Trait == "Hairlessness",], aes(Hypothesis, fill = Result.x)) + geom_histogram() + labs(title="Hairlessness by authors") + labs(x="", y="Count") + theme_grey(base_size=24)
 
−
 
 
−
# Tästä eteenpäin kurkunpäähypoteeseja
 
−
 
 
−
larynx <- ggplot(summary_data[summary_data$Trait == "Larynx",], aes(Result)) + geom_histogram(fill="blue") + labs(x="", y="Count") + labs(title="Larynx in articles") + theme_grey(base_size=24)
 
−
 
 
−
larynx + facet_wrap(~Hypothesis, ncol=3)
 
−
 
 
−
larynx_authors <- ggplot(authors_uniq[authors_uniq$Trait == "Larynx",], aes(Result.x)) + geom_histogram(fill="blue") + labs(x="", y="Count") + labs(title="Larynx by author") + theme_grey(base_size=24)
 
−
 
 
−
larynx_authors + facet_wrap(~Hypothesis, ncol=3)
 
−
 
 
−
ggplot(summary_data[summary_data$Trait == "Larynx",], aes(Hypothesis, fill = Result)) + geom_histogram() + labs(title="Larynx in articles") + labs(x="", y="Count") + theme_grey(base_size=24)
 
−
 
 
−
ggplot(authors_uniq[authors_uniq$Trait == "Larynx",], aes(Hypothesis, fill = Result.x)) + geom_histogram() + labs(title="Larynx by authors") + labs(x="", y="Count") + theme_grey(base_size=24)
 
−
 
 
−
#Tästä eteenpäin puhehypoteeseja
 
−
 
 
−
speech <- ggplot(summary_data[summary_data$Trait == "Speech",], aes(Result)) + geom_histogram(fill="blue") + labs(x="", y="Count", title="Speech in articles") + theme_grey(base_size=24)
 
−
 
 
−
speech + facet_wrap(~Hypothesis, ncol=3)
 
−
 
 
−
speech_authors <- ggplot(authors_uniq[authors_uniq$Trait == "Speech",], aes(Result.x)) + geom_histogram(fill="blue") + labs(x="", y="Count") + labs(title="Speech by author") + theme_grey(base_size=24)
 
−
 
 
−
speech_authors + facet_wrap(~Hypothesis, ncol=3)
 
−
 
 
−
ggplot(summary_data[summary_data$Trait == "Speech",], aes(Hypothesis, fill = Result)) + geom_histogram() + labs(title="Speech in articles") + labs(x="", y="Count") + theme_grey(base_size=24)
 
−
 
 
−
ggplot(authors_uniq[authors_uniq$Trait == "Speech",], aes(Hypothesis, fill = Result.x)) + geom_histogram() + labs(title="Speech by authors") + labs(x="", y="Count") + theme_grey(base_size=24)
 
−
 
 
−
#Tästä eteenpäin muita hypoteeseja
 
−
 
 
−
other <- ggplot(summary_data[summary_data$Trait == "Other",], aes (Result)) + geom_histogram(fill="blue") + labs(x="", y="Count") + labs (title="Other human traits in articles") + theme_grey(base_size=24)
 
−
 
 
−
other + facet_wrap(~Hypothesis, ncol=3)
 
−
 
 
−
other_authors <- ggplot(authors_uniq[authors_uniq$Trait == "Other",], aes (Result.x)) + geom_histogram(fill="blue") + labs(x="", y="Count") + labs (title="Other human traits by author") + theme_grey(base_size=24)
 
  
−
other_authors + facet_wrap(~Hypothesis, ncol=3)
 
  
 
#oprint(odag)
 
#oprint(odag)
Line 367: Line 917:
 
#odag()
 
#odag()
  
−
authors_for <- authors_uniq[authors_uniq$Result.x == "F",]
+
#authors_for <- authors_uniq[authors_uniq$Result.x == "F",]
  
−
oprint(authors_for)
+
#oprint(authors_for)
  
−
authors_against <- authors_uniq[authors_uniq$Result.x == "A",]
+
#authors_against <- authors_uniq[authors_uniq$Result.x == "A",]
  
−
oprint(authors_against)
+
#oprint(authors_against)
  
 
edg <- data.frame(
 
edg <- data.frame(
Line 402: Line 952:
 
   dag,
 
   dag,
 
   vertex.label.cex = 0.4,
 
   vertex.label.cex = 0.4,
−
   vertex.size = ifelse(V(dag)$Type == "Hypothesis", 6, 3),,
+
   vertex.size = ifelse(V(dag)$Type == "Hypothesis", 6, 3),
 +
  vertex.label.family = "Helvetica",
 
   vertex.color = ifelse(V(dag)$Type == "Hypothesis",  
 
   vertex.color = ifelse(V(dag)$Type == "Hypothesis",  
 
                         colo[as.factor(V(dag)$Trait)],
 
                         colo[as.factor(V(dag)$Trait)],
Line 413: Line 964:
 
   asp = 0.7
 
   asp = 0.7
 
)
 
)
 +
  
 
</rcode>
 
</rcode>
−
 
−
=== Literary review summary ===
 
−
 
−
Hidden below you can find a summary of the articles found in a literary review on the evolution of human traits done in the summer 2016 to find out, which hypothesis on which human traits are currently discussed in scientific articles, and which according to them seem the most likely ways the human traits have evolved. F, A and N in the last column stand for For, Against and Neutral, according to which point of view is argued in the article about the hypothesis in question.
 
−
 
−
{{hidden|1=
 
−
 
−
Tämä alla oleva koodi luo uuden sarakkeen observation ja sijoittaa siihen Result-sarakkeiden nimet. Tässä tapauksessa on vain yksi Result-sarake FAN.
 
−
 
−
index="...Trait,observation" locations="FAN"
 
−
 
−
Niitä voisi olla useita, esim kolme saraketta vuosille 2014, 2015, 2016. Tällöin nämä nimet laitettaisiin locationsiin, ja ne sijoitettaisiin allekkain tietokantaan sarakkeeksi Result.
 
−
 
−
index="...Trait,Year" locations="2014,2015,2016"
 
−
 
−
Tämä puolestaan ei luo uutta saraketta vaan näyttää wikisivulla Result-sarakkeen nimenä FAN, vaikka se tallentuukin tietokantaan nimellä Result. Korjaan taulukon tämän mukaiseksi.
 
−
 
−
index="...Trait" obs="FAN"
 
−
 
−
<t2b name="Literary review summary" index="Article,Year,Type,Hypothesis,Trait" obs="For Against Neutral" unit="-">
 
−
Ko 2015-1|2015|Review article|Better view|Bipedalism|A
 
−
Videan & McGrew 2002|2002|Research article|Better view|Bipedalism|A
 
−
Bender et al. 2007|2007|Review article|Better view|Bipedalism|A
 
−
Sutou 2012|2012|Essay|Carrying baby|Bipedalism|F
 
−
Watson et al. 2008|2008|Research article|Carrying baby|Bipedalism|A
 
−
David-Barret & Dunbar 2016|2016|Research article|Carrying food|Bipedalism|A
 
−
Ko 2015-1|2015|Review article|Carrying food|Bipedalism|F
 
−
Videan & McGrew 2002|2002|Research article|Carrying food|Bipedalism|F
 
−
Carvalho et al. 2012|2012|Comment|Carrying food|Bipedalism|F
 
−
Sutou 2012|2012|Essay|Carrying food|Bipedalism|F
 
−
Lieberman 2011|2011|Essay|Energy efficiency|Bipedalism|F
 
−
Rodman & McHenry 1980|1980|Research article|Energy efficiency|Bipedalism|F
 
−
David-Barret & Dunbar 2016|2016|Research article|Energy efficiency|Bipedalism|N
 
−
Sockol et al. 2007|2007|Research article|Energy efficiency|Bipedalism|F
 
−
Leonard & Robertson 1995|1995|Comment|Energy efficiency|Bipedalism|F
 
−
Leonard & Robertson 2001|2001|Comment|Energy efficiency|Bipedalism|F
 
−
Isbell & Young 1996|1996|Review article|Energy efficiency|Bipedalism|F
 
−
Pontzer et al. 2009|2009|Research article|Energy efficiency|Bipedalism|F
 
−
Pickford 2002|2002|Review article|Energy efficiency|Bipedalism|F
 
−
Halsey & White 2012|2012|Research article|Energy efficiency|Bipedalism|A
 
−
Wang et al. 2003|2003|Research article|Energy efficiency|Bipedalism|A
 
−
Steudel 1996|1996|Research article|Energy efficiency|Bipedalism|A
 
−
Taylor & Rowntree 1973|1973|Comment|Energy efficiency|Bipedalism|A
 
−
Steudel-Numbers 2003|2003|Research article|Energy efficiency|Bipedalism|A
 
−
Crompton et al. 1998|1998|Research article|Energy efficiency|Bipedalism|A
 
−
Wheeler 1984|1984|Review article|Energy efficiency|Bipedalism|N
 
−
Carey & Crompton 2005|2005|Research article|Energy efficiency|Bipedalism|N
 
−
Videan & McGrew 2002|2002|Research article|Foraging|Bipedalism|F
 
−
David-Barret & Dunbar 2016|2016|Research article|Thermoregulation-b|Bipedalism|N
 
−
Wheeler 1984|1984|Review article|Thermoregulation-b|Bipedalism|F
 
−
Morgan 1993|1993|Review article|Thermoregulation-b|Bipedalism|A
 
−
Porter 1993|1993|Comment|Thermoregulation-b|Bipedalism|F
 
−
Wheeler 1994|1994|Comment|Thermoregulation-b|Bipedalism|F
 
−
Wheeler 1991-1|1991|Research article|Thermoregulation-b|Bipedalism|F
 
−
Wheeler 1991-2|1991|Research article|Thermoregulation-b|Bipedalism|F
 
−
Ruxton & Wilkinson 2011|2011|Research article|Thermoregulation-b|Bipedalism|A
 
−
Ko 2015-1|2015|Review article|Thermoregulation-b|Bipedalism|A
 
−
Chaplin et al. 1994|1994|Research article|Thermoregulation-b|Bipedalism|A
 
−
Bender et al. 2007|2007|Review article|Thermoregulation-b|Bipedalism|A
 
−
Roberts & Thorpe  2014|2014|Review article|Thinner branches|Bipedalism|F
 
−
Stanford 2006|2006|Research article|Thinner branches|Bipedalism|F
 
−
Crompton et al. 2010|2010|Review article|Thinner branches|Bipedalism|F
 
−
Sigmon 1971|1971|Research article|Thinner branches|Bipedalism|F
 
−
Stanford 2002|2002|Brief communication|Thinner branches|Bipedalism|F
 
−
Senut 2006|2006|Book section|Thinner branches|Bipedalism|F
 
−
Thorpe 2009|2009|Research article|Thinner branches|Bipedalism|F
 
−
Tuttle 1981|1981||Thinner branches|Bipedalism|F
 
−
Preuschoft 2004|2004|Review article|Thinner branches|Bipedalism|F
 
−
Thorpe et al. 2007-1|2007|Report|Thinner branches|Bipedalism|F
 
−
Thorpe et al. 2014|2014|Debate|Thinner branches|Bipedalism|F
 
−
Crompton et al. 2003|2003||Thinner branches|Bipedalism|F
 
−
Gebo 1996|1996|Research article|Thinner branches|Bipedalism|A
 
−
Begun et al. 2007|2007|Comment|Thinner branches|Bipedalism|A
 
−
Thorpe et al. 2007-2|2007|Comment|Thinner branches|Bipedalism|F
 
−
Wheeler 1984|1984|Review article|Tool use|Bipedalism|A
 
−
Harcourt‐Smith 2007|2007|Book section|Tool use|Bipedalism|A
 
−
Bender et al. 1997|1997||Wading|Bipedalism|F
 
−
Morgan 1993|1993|Review article|Wading|Bipedalism|F
 
−
Wrangham et al. 2009|2009|Research article|Wading|Bipedalism|F
 
−
Niemitz 2010|2010|Review article|Wading|Bipedalism|F
 
−
Kuliukas 2002|2002|Research article|Wading|Bipedalism|F
 
−
Kuliukas 2009|2009|Review article|Wading|Bipedalism|F
 
−
Kuliukas et al. 2009|2009|Research article|Wading|Bipedalism|F
 
−
Bender et al. 2007|2007|Review article|Wading|Bipedalism|F
 
−
Isler & van Schaik 2014|2014|Review article|Collaborative hunting|Brain|F
 
−
Carmody & Wrangham 2009|2009|Research article|Cooking|Brain|N
 
−
Joordens et al. 2014|2014|Research article|Fish|Brain|F
 
−
Broadhurst et al. 2002|2002|Review article|Fish|Brain|F
 
−
Broadhurst et al. 1998|1998|Review article|Fish|Brain|F
 
−
Cunnane 2007|2007|Comment|Fish|Brain|F
 
−
Cunnane et al. 2007|2007|Short report|Fish|Brain|F
 
−
Cunnane & Crawford 2003|2003|Review article|Fish|Brain|F
 
−
Cunnane et al. 1993|1993|Research article|Fish|Brain|F
 
−
Cunnane & Crawford 2014|2014|Research article|Fish|Brain|F
 
−
Verhaegen 1995|1995|Brief communication|Fish|Brain|F
 
−
Braun et al. 2010|2010|Research article|Fish|Brain|F
 
−
Carlson & Kingston 2007-1|2007|Research article|Fish|Brain|A
 
−
Carlson & Kingston 2007-2|2007|Comment|Fish|Brain|A
 
−
Langdon 2006|2006|Review article|Fish|Brain|A
 
−
Lakatos & Janka 2008|2008||Language|Brain|F
 
−
Brown & Greenhood 1991|1991|Review article|Language|Brain|F
 
−
Falk 1980|1980|Review article|Language|Brain|F
 
−
Previc 2002|2002|Brief communication|Meat|Brain|F
 
−
Speth 1989|1989|Research article|Meat|Brain|A
 
−
Ibraimov 2007|2007|Review article|Nakedness|Brain|N
 
−
Shea 1989|1989|Review article|Neoteny|Brain|A
 
−
Sandel et al. 2016|2016|Research article|Social|Brain|F
 
−
Shultz & Dunbar 2010|2010|Research article|Social|Brain|F
 
−
Shultz & Dunbar 2007|2007|Review article|Social|Brain|F
 
−
Navarrete et al. 2011|2011|Letter|Social|Brain|F
 
−
Dunbar 1992|1992|Research article|Social|Brain|F
 
−
Dunbar 1998|1998|Research article|Social|Brain|F
 
−
Dunbar 2003|2003|Review article|Social|Brain|F
 
−
Allman 1999|1999|Book section|Social|Brain|A
 
−
Falk 1980|1980|Review article|Warfare|Brain|A
 
−
Pitt 1978|1978|Review article|Warfare|Brain|F
 
−
Pawlowski 1999|1999||Body shape|Fat|N
 
−
Cunnane & Crawford 2003|2003|Review article|Energy supply|Fat|F
 
−
Wells 2006|2006|Research article|Energy supply|Fat|F
 
−
Correia et al. 2004|2004|Research article|Energy supply|Fat|F
 
−
Rebora 2010|2010|Review article|Insulation|Fat|A
 
−
Wheeler 1984|1984|Review article|Savannah thermoregulation|Fat|F
 
−
Pawlowski 1998|1998||Savannah thermoregulation|Fat|F
 
−
Pawlowski 1999|1999||Savannah thermoregulation|Fat|F
 
−
Rantala 2007|2007|Review article|Clothes|Hairlessness|A
 
−
Pagel & Bomder 2003|2003|Letter|Clothes|Hairlessness|N
 
−
Pagel & Bomder 2004|2004|Book section|Clothes|Hairlessness|N
 
−
Rebora 2010|2010|Review article|Clothes|Hairlessness|A
 
−
Kushlan 1985|1985|Review article|Clothes|Hairlessness|N
 
−
Glass 1966|1966|Letter|Clothes|Hairlessness|F
 
−
Hershkovitz 1966|1966|Letter|Clothes|Hairlessness|A
 
−
Brace et al. 1966|1966|Letter|Clothes|Hairlessness|A
 
−
Rantala 2007|2007|Review article|Drag|Hairlessness|A
 
−
Pagel & Bomder 2003|2003|Letter|Drag|Hairlessness|A
 
−
Rebora 2010|2010|Review article|Drag|Hairlessness|A
 
−
Wheeler 1985|1985|Review article|Drag|Hairlessness|A
 
−
Rantala 2007|2007|Review article|Ectoparasites|Hairlessness|F
 
−
Pagel & Bomder 2003|2003|Letter|Ectoparasites|Hairlessness|F
 
−
Rantala 1999|1999|Discussion|Ectoparasites|Hairlessness|F
 
−
Dean & Siva-Jothy 2012|2012|Letter|Ectoparasites|Hairlessness|F
 
−
Pagel & Bomder 2004|2004|Book section|Ectoparasites|Hairlessness|F
 
−
Dunn 1966|1966|Comment|Ectoparasites|Hairlessness|A
 
−
Rebora 2010|2010|Review article|Ectoparasites|Hairlessness|A
 
−
Giles 2011|2011|Review article|Skin contact baby|Hairlessness|F
 
−
Giles 2011|2011|Review article|Skin contact sex|Hairlessness|F
 
−
Rantala 2007|2007|Review article|Skin contact sex|Hairlessness|A
 
−
Wheeler 1984|1984|Review article|Thermoregulation-h|Hairlessness|F
 
−
Ruxton & Wilkinson 2011|2011|Research article|Thermoregulation-h|Hairlessness|F
 
−
Ibraimov 2007|2007|Review article|Thermoregulation-h|Hairlessness|F
 
−
Rantala 2007|2007|Review article|Thermoregulation-h|Hairlessness|A
 
−
Pagel & Bomder 2003|2003|Letter|Thermoregulation-h|Hairlessness|A
 
−
Rebora 2010|2010|Review article|Thermoregulation-h|Hairlessness|A
 
−
Wheeler 1985|1985|Review article|Thermoregulation-h|Hairlessness|F
 
−
Schwarts & Rosenblum 2005|2005|Research article|Thermoregulation-h|Hairlessness|F
 
−
Lupi 2008|2008|Review article|Thermoregulation-h|Hairlessness|F
 
−
Wheeler 1996|1996|Comment|Thermoregulation-h|Hairlessness|F
 
−
Wheeler 1992|1992|Research article|Thermoregulation-h|Hairlessness|F
 
−
Ebling 1985|1985|Review article|Thermoregulation-h|Hairlessness|F
 
−
Kushlan 1985|1985|Review article|Thermoregulation-h|Hairlessness|F
 
−
Brace et al. 1966|1966|Letter|Thermoregulation-h|Hairlessness|F
 
−
Amaral 1996|1966|Review article|Thermoregulation-h|Hairlessness|N
 
−
Davidson 2003|2003|Review article|Articulation|Larynx|F
 
−
Shprintzen 2003|2003|Comment|Articulation|Larynx|A
 
−
Nishimura et al. 2006|2006|Research article|Articulation|Larynx|A
 
−
Frey et al. 2011|2011||Impressive voice|Larynx|F
 
−
Frey et al. 2015|2015|Research article|Impressive voice|Larynx|F
 
−
Hombert 2010|2010|Book section|Impressive voice|Larynx|F
 
−
Fitch & Reby 2001|2001|Research article|Impressive voice|Larynx|F
 
−
Fitch 2002|2002|Review article|Impressive voice|Larynx|F
 
−
Apicella & Feinberg 2009|2009|Research article|Impressive voice|Larynx|N
 
−
Apicella et al. 2007|2007|Letter|Impressive voice|Larynx|N
 
−
Falhman & Schagatey 2014|2014|Review article|Diving-o|Other|F
 
−
Schagatey 2011|2011|Book section|Diving-o|Other|F
 
−
Verhaegen 1993|2013|Review article|Nose|Other|F
 
−
Mladina et al. 2009|2009|Review article|Nose|Other|N
 
−
Verhaegen 1995|1995|Brief communication|Smell|Other|F
 
−
Verhaegen et al. 2007|2007|Book section|Smell|Other|F
 
−
Wheeler 1991-2|1991|Research article|Sweating|Other|A
 
−
Wheeler 1992|1992|Research article|Sweating|Other|A
 
−
MacLarnon & Hewitt 1999|1999|Research article|Bipedalism-s|Speech|A
 
−
Stout & Chaminade 2012|2012|Review article|Culture|Speech|F
 
−
Corballis 2009|2009|Book section|Culture|Speech|F
 
−
Verhaegen 1995|1995|Brief communication|Diving-s|Speech|F
 
−
Verhaegen et al. 2002|2002|Opinion|Diving-s|Speech|F
 
−
MacLarnon & Hewitt 1999|1999|Research article|Diving-s|Speech|A
 
−
Lieberman 1973|1973|Review article|Hunting|Speech|N
 
−
Shprintzen 2003|2003|Comment|Larynx|Speech|A
 
−
Nishimura et al. 2006|2006|Research article|Larynx|Speech|A
 
−
Falk 2004|2004|Review article|Reassurance|Speech|F
 
−
Brown & Greenhood 1991|1991|Review article|Sociality|Speech|F
 
−
Dunbar 1993|1993||Sociality|Speech|F
 
−
Hamilton 1974|1974|Review article|Sociality|Speech|F
 
−
Kurland & Beckerman 1985|1985||Sociality|Speech|F
 
−
Locke 2001|2001|Review article|Sociality|Speech|F
 
−
Ko 2015-2|2015|Review article|Sociality|Speech|N
 
−
</t2b>
 
−
 
−
}}
 
  
 
== See also ==
 
== See also ==

Latest revision as of 20:20, 13 November 2016



Question

Why and how did humans become so different from other apes?

Answer

Rationale

Hypotheses

There are conflicting hypotheses to explain why the traits that so clearly distinguish humans from other primates originally evolved. One idea is that the ancestors of humans came to live in a different kind of environment than the ancestors of chimpanzees and gorillas, and hence experienced different selection pressures and obtained a suite of unique traits as adaptations to the new environment. What that new environment was and which selection pressures were most important has been debated, however, and a number of hypotheses based on ideas other than environmental adaptation have also been proposed. To date, general discussion on the topic seems mostly to have focused on finding merit or flaws in one hypothesis at a time. The purpose of this page is to provide a structured forum for the general evaluation and comparison of the different hypotheses on human origins.

Below you can find a list of hypotheses explaining different traits that separate humans from other great apes. They were a part of a survey done on people's understanding about the reasons behind human traits, answered by paleontologist, biologists, medical professionals, and other people with professional understanding about evolution (human or in general) or how human bodies work. Some analysis done on the survey answers can be found below. Some hypotheses much discussed in literature in the last years are missing from the survey (and thus he list below), such as the postural feeding hypothesis, stating bipedalism originally arose as a feeding posture and not as a way of locomotion, and the expensive tissue hypothesis, which suggests the energy needed for building a big brain came from reducing some other expensive tissue in our body, namely the gut. A literary review was done on the same hypotheses asked about in the survey to find out whether the understanding about human evolution the answerers had was the same that could be gotten from scientific literature published in the last decades. Some analysis on the literary review results is found on this page.

The short version of the hypotheses in the list below are the ones used to refer to them in the analysis.

Hypotheses and their shorter versions
For short Hypothesis
Bipedalism
Energy efficiency When covering long distances on the ground, walking or running erect on two legs is energetically more efficient than walking or running on four legs.
Thinner branches In the canopy, walking erect facilitates using multiple supports (as in orangutans) and hence makes it possible to move on thinner branches than when brachiating or moving quadrupedally.
Wading In a littoral habitat, walking erect allows wading in deeper water with the nostrils above the surface (apes cross water bodies bipedally), and the same posture increases streamlining when swimming and diving for food (as in penguins).
Thermoregulation-b Walking erect helps in thermoregulation in the savanna by exposing less skin to the midday sun and more skin to cooling wind.
Better view Walking erect makes it possible to see above the savanna grass and hence spot danger from further away.
Foraging Walking erect makes foraging more efficient, because hands are not needed for locomotion.
Carrying food Walking erect makes it easier for a male to carry high-quality food such as meat to the female and infants.
Carrying baby Walking erect makes it possible for a female to carry its offspring in its arms.
Tool use Walking erect makes it easier to use tools and weapons.
Genitals Walking erect is favored by sexual selection, as it makes the genitals more visible.
Big brain
Meat A shift in diet towards eating more meat triggers encephalization, because meat is rich in energy.
Fish A shift in diet towards eating more fish and other seafood triggers encephalization, because seafood is rich in both energy and the omega-3 fatty acids that are an essential component of brain tissue.
Cooking The use of fire triggers encephalization, because cooking increases the nutritional value of plant foods.
Social Complex social organization causes pressure for greater intelligence and hence triggers encephalization.
Collaborative hunting Collaborative hunting causes pressure for greater intelligence and hence triggers encephalization.
Language Spoken language causes pressure for greater intelligence and hence triggers encephalization.
Warfare Warfare causes pressure for greater intelligence and hence triggers encephalization.
Neoteny Encephalization is a secondary effect of neoteny (the retention of juvenile features into adulthood), which is advantageous when specialized adult morphology adapted to one environment has become maladaptive in a new environment.
Bipedalism-b Encephalization is triggered by bipedalism, which changes the blood circulation and provides a cooling mechanism for the larger brain.
Nakedness Encephalization is triggered by nakedness, which provides a cooling mechanism for the larger brain.
Nakedness
Skin contact baby Direct skin-to-skin contact strengthens the emotional bond between a female and its nursing offspring.
Skin contact sex Direct skin-to-skin contact makes sex more enjoyable, and is favored by sexual selection.
Cleanliness In animals that feed messily on carrion, naked skin stays cleaner than hairy skin (or feather-covered skin as in vultures).
Ectoparasites In mammals that live in permanent nests, naked skin helps to avoid a high ectoparasite load.
Drag In mammals that live partly or entirely entirely in water, fur is often lost because it causes drag when swimming but fails to provide efficient insulation when wet (e.g. walrus, hippopotamuses, dolphins).
Thermoregulation-h In mammals that hunt on the savanna, naked skin dissipates heat more efficiently and reduces the risk of becoming overheated.
Large mammal Large mammals can regulate their body temperature without investing in hair, and humans are relatively large compared to other primates.
Clothes Once the use of clothes has become common, fur becomes unnecessary.
Subcutaneous fat
Energy supply In conditions of variable food supply, subcutaneous fat can store energy for times of food scarcity, and in infants it secures the development of the large brain.
Insulation In wet conditions, subcutaneous fat provides more efficient insulation than hair does, and it makes swimming easier by increasing buoyancy and streamlining of the body.
Savannah thermoregulation Subcutaneous fat is an adaptation to thermoregulation in the savanna, together with nakedness and sweating.
Body shape Subcutaneous fat defines the body shape and its evolution is driven by sexual selection.
Descended larynx
Articulation Articulate speech requires a descended larynx, because this makes it possible to produce a wider variety of sounds.
Impressive voice A descended larynx makes the voice stronger and more impressive, and can evolve through sexual selection (as in the males of some deer).
Diving-l A descended larynx can evolve as an adaptation to diving (as in some aquatic mammals), because it makes it possible to close the air passages when under water and to inhale rapidly through the mouth when surfacing.
Speech
Larynx Speech is triggered by the descended larynx, which allows making a wider variety of sounds.
Diving-s Speech requires voluntary breath control, which can evolve as an adaptation to diving. In water, visual and olfactory cues are inadequate and therefore liable to be replaced by vocal communication (as in whales).
Bipedalism-s Speech requires voluntary breath control, which can evolve after bipedalism frees breathing from the constraint posed by the mechanics of locomotion.
Reassurance Speech provides a means for females to reassure their offspring who have to be put down while foraging.
Sociality Social pressure for more elaborate communication triggers evolution of speech.
Hunting Collective hunting requires a means of effective communication and therefore triggers evolution of speech.
Culture Transmitting cultural tradition (e.g., how to cope with unusually severe droughts) from one generation to the next requires a means of effective communication and therefore triggers evolution of speech.
Other traits that could be explained by an aquatic phase in human evolution
Baby swimming Human babies can be taken for a swim long before they can walk. They are comfortable in water and capable of holding their breath when submerged.
Nose Unlike apes, humans have an arched nose and flexible nostrils. These help prevent water from entering the respiratory tract when diving.
Smell Humans have a relatively weak sense of smell, as aquatic mammals often do.
Webbing Humans have partial webbing between their fingers and toes. Webbed feet are common among semi-aquatic animals (such as otters and ducks), but are not found in non-human primates.
Eccrine glands Cooling sweat is excreted from eccrine glands in humans but from apocrine glands in other primates. Apocrine glands could have lost their thermoregulatory function in human ancestors during a period when dip-cooling replaced sweat-cooling.
Sweating Humans sweat more profusely than any other primate. Since this can lead to fatal loss of water and electrolytes in a few hours, the trait probably evolved in conditions of abundant water and salt supply.
Diving-o Compared to other primates, humans are stronger swimmers and can dive both deeper and further.
Apnea The diving reflex (slowing down of heartbeat and oxygen usage in water) increases the resistance of the brain to apnea, and its magnitude in human divers is comparable to that in semi-aquatic mammals such as otters and beavers.
Fond of water Compared to other primates, humans are unusually fond of immersing themselves in water. This is manifested in the popularity of beach holidays, swimming and bathing.

The answerers' opinions should be used as continuous [0,1] variables in such a way that each answer is transformed into its quantile of all answers to that question. Then neural networks, Bayesian belief network analyzers (such as B-source), or other statistical tools can be applied.

For single answer analyses, multinomial regression models should be applied.

In the following sections, we will present results about support to different hypotheses explaining the traits studied. We have two sources of information and three graphs for each hypothesis: Survey to authors of relevant journals, with ca. 1200 responses; and authors of articles about human evolution and the traits of interest (272 individual authors). The survey graphs on the left show the repondents' views on how likely each hypothesis is. The middle graphs show the same information separated by the expertise of the respondent (and for visibility, we assumed the X axis to be continous so that we could draw probability densities). The graphs on the right show the support from article authors in the literature review. Each hypothesis has one row of graphs, and they are ordered by the trait the hypotheses explain.

Bipedalism

Brain

Nakedness

Subcutaneous fat

Larynx

Speech

Other traits

Survey

Error creating thumbnail: Unable to save thumbnail to destination

The graph above shows the results for correlations done from the survey answers between all different hypotheses. In most cases the correlations were quite small, and almost always positive. There are only a few negative correlations in these answers, and in them the correlations are very small, -0.14 being the strongest negative correlation. The most notable correlations are between the hypotheses that suggest a semi-aquatic ancestor. If one believes in one, then all the water-relates hypotheses seem likely, and if one doesn't, they seem unlikely. Interestingly, eating of fish and other sea food enabling brain growth does not correlate with the rest of the water-related hypotheses, even though if fish was needed for brain growth, it indicades humans lived on shores, fishing and wading, thus probably spending a significant time in water, which is also the basis for all the other waterside hypotheses. The fish hypothesis does however have a correlation with eating meat being a major step toward bigger brains, as well as cooking the food, which makes it possible to get more energy from it.

The graph below shows the results for principal components analysis done on the survey data. All the water-related hypotheses (except eating fish) are at the top right corner, and the rest are at the bottom. This means those people who have an opinion about one water-related hypothesis are more or less the same opinion about the rest of them. What people thought about the water-related hypotheses doesn't seem to have much of a connection to their opinions about the rest of the hypotheses.

For other hypotheses it seems that the idea that brain developed as a response to hairlessness convinces the same people as the hypotheses of hairlessness evolving to enhance skin contact and bipedalism to show off genitals. Completely different people were the people who found it convincing that the brain developed to enable speaking or hunting and that the subcutaneous fat layer developed as an energy supply.

The sizes for the dots tell about how likely the hypothesis was found to explain the trait in the survey. The bigger the dot, the more likely people thought it was. The numbers from the scaling were gotten by calculating the average answer (1 being very likely and 5 being very unlikely), and subtracting that from 5 (to get the likeliest ones with the highest values instead of the lowest).

Error creating thumbnail: Unable to save thumbnail to destination

Literary review

Hidden below you can find a summary of the articles found in a literary review on the evolution of human traits done in the summer 2016 to find out, which hypothesis on which human traits are currently discussed in scientific articles, and which according to them seem the most likely ways the human traits have evolved. F, A and N in the last column stand for For, Against and Neutral, according to which point of view is argued in the article about the hypothesis in question.



There are may histograms drawn from the review data to show how many of the found articles support or argue against all of the different hypotheses. They also show which hypotheses are the most talked about in the literature. Another set of histograms were drawn from the amount of authors writing the articles about each of the hypotheses. For this, all the authors for all articles were listed and plotted the same way as he articles, being for, against or writing something neural about the hypothesis. Before drawing the histograms the data was processed so that one author was counted only once to support or oppose a certain hypothesis, even if they had authored more than one article on the topic. You can see the histograms by trait from the authors below. Green color means supporting, red opposing and blue writing something neutral about the topic. All of the histograms can be found here and here. Note that not all of the hypotheses in the survey were discussed at all in any of the articles in the literature review.

Error creating thumbnail: Unable to save thumbnail to destination
Error creating thumbnail: Unable to save thumbnail to destination

The lower graph above shows relations between writers (small dots) and hypotheses (bubbles), or how the different writers wrote about hypotheses. Green lines mean supporting, red lines mean arguing against, and grey lines mean writing something on the topic, but not being clearly for or against the hypothesis. It shows us which hypotheses are discussed by the same authors, and whether the author supported both, opposed both, or whether they're hypotheses that one person doesn't think likely to both be true.

Several observations can be made from the graph. First, most authors only discussed a single hypothesis. The maximum number of different hypothesis discussed by a single author was six --# : CHECK THE DATA --Jouni (talk) 12:48, 4 September 2016 (UTC), but few authors discussed more than two hypotheses.

Second, some areas, notably nakedness, stimulated many authors to discuss several possible hypotheses. Another similar area was bipedalism, where, interestingly, authors supporting thinner branch hypothesis simultaneously opposed energy efficiency hypothesis. However, in the survey data these two hypotheses were not correlated.

Third, there are some isolated hypotheses such as neoteny, culture, and impressive voice, where the authors of these topics did not discuss any of the other hypotheses, and also none of the other authors discussed these hypotheses.

It can be concluded that there is no single study that would systematically look at the evolution of important human traits and evaluate strengths and weaknesses of related hypotheses.

Student survey

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Hypotheses and reasonings related to bipedalism.
A questionnaire was sent to students to study whether they found the reasoning of each hypothesis convincing.



+ Show code

Calculations

calc1

+ Show code


number of X column (1-25):

number of fill column (empty = all):

Encryption key:

+ Show code

Histograms

A code for drawing histograms from the literary review data showing the number of articles and and authors supporting and arguing against different hypotheses. You can see all the histograms by clicking "Run code".

+ Show code

See also

Human evolution hypotheses described in Wikipedia:

Keywords

Human evolution, Bipedalism, Brain, Hairnessless, Subcutaneous fat, Speech

References


Related files

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