Editing Human evolution (section)

== Anatomical changes ==
Since ''[[Homo sapiens]]'' separated from its [[Chimpanzee–human last common ancestor|last common ancestor]] shared with [[chimpanzee]]s, human evolution is characterized by a number of [[Morphology (biology)|morphological]], [[Human development (biology)|developmental]], [[Human physiology|physiological]], [[Human behavior|behavioral]], and environmental changes.<ref name="Marlowe 54–67" /> Environmental (cultural) evolution discovered much later during the [[Pleistocene]] played a significant role in human evolution observed via human transitions between subsistence systems.<ref>{{Cite journal |last=Clark |first=Jamie L. |date=September 2011 |title=The evolution of human culture during the later Pleistocene: Using fauna to test models on the emergence and nature of "modern" human behavior |url= https://linkinghub.elsevier.com/retrieve/pii/S0278416511000225 |journal=Journal of Anthropological Archaeology |volume=30 |issue=3 |pages=273–291 |doi=10.1016/j.jaa.2011.04.002 |access-date=October 27, 2021 |archive-date=May 25, 2021 |archive-url= https://web.archive.org/web/20210525182055/https://linkinghub.elsevier.com/retrieve/pii/S0278416511000225 |url-status=live}}</ref><ref name="Marlowe 54–67" /> The most significant of these adaptations are bipedalism, increased brain size, lengthened [[ontogeny]] (gestation and infancy), and decreased [[sexual dimorphism]]. The relationship between these changes is the subject of ongoing debate.{{sfn|Boyd|Silk|2003|p={{Page needed|date=February 2015}}}} Other significant morphological changes included the evolution of a [[Thumb#Grips|power and precision grip]], a change first occurring in ''[[H.&nbsp;erectus]]''.{{sfn|Brues|Snow|1965|pp=[https://books.google.com/books?id=9WemAAAAIAAJ&pg=PA1 1–39]}}

=== Bipedalism ===
[[File:Akha cropped.png|thumb|upright|Bipedalism shown by a man and a woman]]

[[Bipedalism]] (walking on two legs) is the basic adaptation of the hominid and is considered the main cause behind a suite of skeletal changes shared by all bipedal hominids. The earliest hominin, of presumably primitive bipedalism, is considered to be either ''[[Sahelanthropus]]''<ref name="Brunet2002">{{cite journal |last1=Brunet |first1=M. |last2=Guy |first2=F. |last3=Pilbeam |first3=D. |last4=Mackaye |first4=H. |last5=Likius |first5=A. |last6=Ahounta |first6=D. |last7=Beauvilain |first7=A. |last8=Blondel |first8=C. |last9=Bocherens |first9=H. |last10=Boisserie |first10=J. |last11=De Bonis |first11=L. |last12=Coppens |first12=Y. |last13=Dejax |first13=J. |last14=Denys |first14=C. |last15=Duringer |first15=P. |last16=Eisenmann |first16=V. |last17=Fanone |first17=G. |last18=Fronty |first18=P. |last19=Geraads |first19=D. |last20=Lehmann |first20=T. |last21=Lihoreau |first21=F. |last22=Louchart |first22=A. |last23=Mahamat |first23=A. |last24=Merceron |first24=G. |last25=Mouchelin |first25=G. |last26=Otero |first26=O. |last27=Pelaez Campomanes |first27=P. |last28=Ponce De Leon |first28=M. |last29=Rage |first29=J. |last30=Sapanet |first30=M. |last31=Schuster |first31=M. |last32=Sudre |first32=J. |last33=Tassy |first33=P. |last34=Valentin |first34=X. |last35=Vignaud |first35=P. |last36=Viriot |first36=L. |last37=Zazzo |first37=A. |last38=Zollikofer |first38=C. |display-authors=6 |author1-link=Michel Brunet (paleontologist) |author3-link=David Pilbeam |date=July 11, 2002 |title=A new hominid from the Upper Miocene of Chad, Central Africa |journal=[[Nature (journal)|Nature]] |volume=418 |issue=6894 |pages=145–151 |doi=10.1038/nature00879 |issn=0028-0836 |pmid=12110880 |bibcode=2002Natur.418..145B |s2cid=1316969 |url= http://doc.rero.ch/record/13388/files/PAL_E190.pdf |access-date=February 20, 2023 |archive-date=February 25, 2023 |archive-url= https://web.archive.org/web/20230225204437/https://doc.rero.ch/record/13388/files/PAL_E190.pdf |url-status=live}}}{{collapsible list |title=Full list of authors |bullets=true |Michel Brunet |Franck Guy |David Pilbeam |Hassane Taisso Mackaye |Andossa Likius |Djimdoumalbaye Ahounta |Alain Beauvilain |Cécile Blondel |Hervé Bocherens |Jean-Renaud Boisserie |Louis De Bonis |Yves Coppens |Jean Dejax |Christiane Denys |Philippe Duringer |Véra Eisenmann |Gongdibé Fanone |Pierre Fronty |Denis Geraads |Thomas Lehmann |Fabrice Lihoreau |Antoine Louchart |Adoum Mahamat |Gildas Merceron |Guy Mouchelin |Olga Otero |Pablo Pelaez Campomanes |Marcia Ponce De Leon |Jean-Claude Rage |Michel Sapanet |Mathieu Schuster |Jean Sudre |Pascal Tassy |Xavier Valentin |Patrick Vignaud |Laurent Viriot |Antoine Zazzo |Christoph Zollikofer}}</ref> or ''[[Orrorin]]'', both of which arose some 6 to 7&nbsp;million years ago. The non-bipedal knuckle-walkers, the [[gorilla]]s and chimpanzees, diverged from the hominin line over a period covering the same time, so either ''Sahelanthropus'' or ''Orrorin'' may be our last shared ancestor. ''[[Ardipithecus]]'', a full biped, arose approximately 5.6&nbsp;million years ago.<ref>{{cite journal |title=Ardipithecus ramidus and the Paleobiology of Early Hominids |journal=[[Science (journal)|Science]] |volume=326 |issue=5949 |pages=75–86 |date=2009 |last1=White |first1=T. D. |last2=Asfaw |first2=B. |last3=Beyene |first3=Y. |last4=Haile-Selassie |first4=Y. |last5=Lovejoy |first5=C. O. |last6=Suwa |first6=G. |last7=Woldegabriel |first7=G. |pmid=19810190 |bibcode=2009Sci...326...75W |s2cid=20189444 |doi=10.1126/science.1175802}}</ref>

The early bipeds eventually evolved into the australopithecines and still later into the genus ''[[Homo]]''. There are several theories of the adaptation value of bipedalism. It is possible that bipedalism was favored because it freed the hands for reaching and carrying food, saved energy during locomotion,<ref name="Kwang Hyun 2015 929–934">{{Cite journal |last=Kwang Hyun |first=Ko |date=2015 |title=Origins of Bipedalism |journal=Brazilian Archives of Biology and Technology |doi=10.1590/S1516-89132015060399 |volume=58 |issue=6 |pages=929–934 |arxiv=1508.02739 |bibcode=2015arXiv150802739K |s2cid=761213}}</ref> enabled long-distance running and hunting, provided an enhanced field of vision, and helped avoid hyperthermia by reducing the surface area exposed to direct sun; features all advantageous for thriving in the new savanna and woodland environment created as a result of the East African Rift Valley uplift versus the previous closed forest habitat.<ref name="Kwang Hyun 2015 929–934" />{{sfn|DeSalle|Tattersall|2008|p=[https://books.google.com/books?id=Bf4Sitw7YaIC&pg=PA146 146]}}{{sfn|Curry|2008|pp=106–109}} A 2007 study provides support for the hypothesis that bipedalism evolved because it used less energy than quadrupedal knuckle-walking.<ref>{{cite news |date=July 17, 2007 |title=Study Identifies Energy Efficiency as Reason for Evolution of Upright Walking |work=[[ScienceDaily]] |url= https://www.sciencedaily.com/releases/2007/07/070716191140.htm |access-date=April 9, 2015 |archive-date=May 4, 2015 |archive-url= https://web.archive.org/web/20150504174649/http://www.sciencedaily.com/releases/2007/07/070716191140.htm |url-status=live}}<br />{{cite web |url= http://uanews.org/story/study-identifies-energy-efficiency-reason-evolution-upright-walking |title=Study identifies energy efficiency as reason for evolution of upright walking |date=July 16, 2007 |website=UANews |publisher=[[University of Arizona]] |location=Tucson |access-date=April 23, 2015 |archive-date=July 3, 2022 |archive-url= https://web.archive.org/web/20220703195556/http://uanews.org/story/study-identifies-energy-efficiency-reason-evolution-upright-walking |url-status=usurped}}</ref><ref>{{cite journal |last1=Sockol |first1=Michael D. |last2=Raichlen |first2=David A. |last3=Pontzer |first3=Herman |date=July 24, 2007 |title=Chimpanzee locomotor energetics and the origin of human bipedalism |journal=[[Proceedings of the National Academy of Sciences of the United States of America]] |volume=104 |issue=30 |pages=12265–12269 |doi=10.1073/pnas.0703267104 |issn=0027-8424 |pmc=1941460 |pmid=17636134 |bibcode=2007PNAS..10412265S |doi-access=free}}</ref> However, recent studies suggest that bipedality without the [[Control of fire by early humans|ability to use fire]] would not have allowed global dispersal.<ref>{{cite journal |last1=David-Barrett |first1=T. |last2=Dunbar |first2=R. I. M. |date=2016 |title=Bipedality and Hair-loss Revisited: The Impact of Altitude and Activity Scheduling |journal=Journal of Human Evolution |volume=94 |pages=72–82 |pmid=27178459 |pmc=4874949 |doi=10.1016/j.jhevol.2016.02.006}}</ref> This change in gait saw a lengthening of the legs proportionately when compared to the length of the arms, which were shortened through the removal of the need for [[brachiation]]. Another change is the shape of the big toe. Recent studies suggest that australopithecines still lived part of the time in trees as a result of maintaining a grasping big toe. This was progressively lost in habilines.

Anatomically, the evolution of bipedalism has been accompanied by a large number of skeletal changes, not just to the legs and pelvis, but also to the [[Human vertebral column|vertebral column]], feet and ankles, and skull.{{sfn|Aiello|Dean|1990}} The [[femur]] evolved into a slightly more angular position to move the center of gravity toward the geometric center of the body. The knee and ankle joints became increasingly robust to better support increased weight. To support the increased weight on each vertebra in the upright position, the human vertebral column became S-shaped and the [[lumbar vertebrae]] became shorter and wider. In the feet the big toe moved into alignment with the other toes to help in forward locomotion. The arms and forearms shortened relative to the legs making it easier to run. The [[foramen magnum]] migrated under the skull and more anterior.{{sfn|Kondo|1985}}

The most significant changes occurred in the pelvic region, where the long downward facing [[Ilium (bone)|iliac blade]] was shortened and widened as a requirement for keeping the center of gravity stable while walking;{{sfn|Srivastava|2009|p=[https://books.google.com/books?id=kCerOsM8XMwC&pg=PA87 87]}} bipedal hominids have a shorter but broader, bowl-like pelvis due to this. A drawback is that the birth canal of bipedal apes is smaller than in knuckle-walking apes, though there has been a widening of it in comparison to that of australopithecine and modern humans, thus permitting the passage of newborns due to the increase in cranial size. This is limited to the upper portion, since further increase can hinder normal bipedal movement.{{sfn|Strickberger|2000|pp=[https://books.google.com/books?id=feMItLo5gwgC&pg=PA476 475–476]}}

The shortening of the pelvis and smaller birth canal evolved as a requirement for bipedalism and had significant effects on the process of human birth, which is much more difficult in modern humans than in other primates. During human birth, because of the variation in size of the pelvic region, the fetal head must be in a transverse position (compared to the mother) during entry into the birth canal and rotate about 90 degrees upon exit.{{sfn|Trevathan|2011|p=[https://books.google.com/books?id=Potlqpl-jxgC&pg=PA20 20]}} The smaller birth canal became a limiting factor to brain size increases in early humans and prompted a shorter gestation period leading to the relative immaturity of human offspring, who are unable to walk much before 12 months and have greater [[neoteny]], compared to other primates, who are mobile at a much earlier age.{{sfn|Curry|2008|pp=106–109}} The increased brain growth after birth and the increased dependency of children on mothers had a major effect upon the female reproductive cycle,<ref>{{cite book |last=Zuk |first=Marlene |date=2014 |title=Paleofantasy: What Evolution Really Tells Us About Sex, Diet, and How We Live |publisher=W.W. Norton & Company |isbn=978-0-393-34792-0 |oclc=846889455}}{{page needed|date=December 2021}}</ref> and the more frequent appearance of [[alloparenting]] in humans when compared with other hominids.<ref>{{cite book |last=Hrdy |first=Sarah Blaffer |date=2011 |title=Mothers and Others: The Evolutionary Origins of Mutual Understanding |publisher=Harvard University Press |isbn=978-0-674-06032-6 |oclc=940575388}}{{page needed|date=December 2021}}</ref> Delayed human sexual maturity also led to the evolution of [[menopause]] with one explanation, the [[grandmother hypothesis]], providing that elderly women could better pass on their genes by taking care of their daughter's offspring, as compared to having more children of their own.<ref>{{cite journal |last=Wayman |first=Erin |date=August 19, 2013 |title=Killer whales, grandmas and what men want: Evolutionary biologists consider menopause |url= https://www.sciencenews.org/article/killer-whales-grandmas-and-what-men-want-evolutionary-biologists-consider-menopause |journal=[[Science News]] |issn=0036-8423 |access-date=April 24, 2015 |archive-date=November 6, 2014 |archive-url= https://web.archive.org/web/20141106194849/https://www.sciencenews.org/article/killer-whales-grandmas-and-what-men-want-evolutionary-biologists-consider-menopause |url-status=live}}</ref><ref>{{Cite journal |last=Blell |first=Mwenza |date=September 29, 2017 |title=Grandmother Hypothesis, Grandmother Effect, and Residence Patterns |journal=The International Encyclopedia of Anthropology |pages=1–5 |doi=10.1002/9781118924396.wbiea2162 |isbn=978-1-118-92439-6 |doi-access=free}}</ref>

=== Encephalization ===
[[File:Skull evolution.png|center|thumb|920px|Skulls of successive (or near-successive, depending on the source) human evolutionary ancestors,{{efn|There is no general agreement on the line of [[species|special]] descent of ''H. sapiens'' from ''H. erectus''. Some of the species depicted in the image may not actually represent a direct evolutionary ancestor to ''H. sapiens'', and may not directly derive from one another, namely:

* ''H. heidelbergensis'' likely did not descend from ''H. antecessor''.<ref name="Welker2020">{{Cite journal |doi=10.1038/s41586-020-2153-8 |issn=1476-4687 |volume=580 |issue=7802 |pages=235–238 |last1=Welker |first1=F. |last2=Ramos-Madrigal |first2=J. |last3=Gutenbrunner |first3=P. |display-authors=etal |title=The dental proteome of ''Homo antecessor'' |journal=[[Nature (journal)|Nature]] |date=April 1, 2020 |pmid=32269345 |pmc=7582224 |bibcode=2020Natur.580..235W |s2cid=214736611 |url= http://eprints.whiterose.ac.uk/159068/1/Welker_etal_Hominin1_AAM.docx |access-date=November 10, 2021 |archive-date=November 10, 2021 |archive-url= https://web.archive.org/web/20211110200345/https://eprints.whiterose.ac.uk/159068/1/Welker_etal_Hominin1_AAM.docx |url-status=live}}{{collapsible list |title=Full list of authors |bullets=true |Frido Welker |Jazmín Ramos-Madrigal |Petra Gutenbrunner |Meaghan Mackie |Shivani Tiwary |Rosa Rakownikow Jersie-Christensen |Cristina Chiva |Marc R. Dickinson |Martin Kuhlwilm |Marc de Manuel |Pere Gelabert |María Martinón-Torres |Ann Margvelashvili |Juan Luis Arsuaga |Eudald Carbonell |Tomas Marques-Bonet |Kirsty Penkman |Eduard Sabidó |Jürgen Cox |Jesper V. Olsen |David Lordkipanidze |Fernando Racimo |Carles Lalueza-Fox |José María Bermúdez de Castro |Eske Willerslev |Enrico Cappellini}}</ref>
* ''H. heidelbergensis'' is likely not an ancestor to ''H. sapiens'', nor is ''H. antecessor''.<ref name="Welker2020" />
* ''H. ergaster'' is often considered the next evolutionary ancestor to ''H. sapiens'' following ''H. erectus'', however, there is considerable uncertainty as to the accuracy of classifying it as a separate species from ''H. erectus'' at all.<ref>{{Cite journal |last1=Dennell |first1=Robin |last2=Roebroeks |first2=Wil |date=2005 |title=An Asian perspective on early human dispersal from Africa |journal=[[Nature (journal)|Nature]] |volume=438 |issue=7071 |pages=1099–1104 |doi=10.1038/nature04259 |pmid=16371999 |bibcode=2005Natur.438.1099D |s2cid=4405913 |url= https://www.nature.com/articles/nature04259 |access-date=November 10, 2021 |archive-date=October 31, 2021 |archive-url= https://web.archive.org/web/20211031154723/https://www.nature.com/articles/nature04259 |url-status=live}}</ref>}} up until 'modern' ''Homo sapiens''<br /> * [[Mya (unit)|Mya]] – million years ago, [[kya (unit)|kya]] – thousand years ago]]
[[File:Brain size and tooth size in hominins.jpg|thumb|upright=1.5|Brain size and tooth size in hominins]]
The human species eventually developed a much larger brain than that of other primates—typically {{convert|1330|cm3|abbr=on}} in modern humans, nearly three times the size of a chimpanzee or gorilla brain.<ref name="Schoeneman">{{cite journal |last=Schoenemann |first=P. Thomas |date=October 2006 |title=Evolution of the Size and Functional Areas of the Human Brain |journal=[[Annual Review of Anthropology]] |volume=35 |pages=379–406 |doi=10.1146/annurev.anthro.35.081705.123210 |s2cid=7611321 |issn=0084-6570}}</ref> After a period of stasis with ''Australopithecus anamensis'' and ''Ardipithecus'', species which had smaller brains as a result of their bipedal locomotion,<ref>{{cite web |last1=Brown |first1=Graham |last2=Fairfax |first2=Stephanie |last3=Sarao |first3=Nidhi |title=Tree of Life Web Project: Human Evolution |url= http://tolweb.org/treehouses/?treehouse_id=3710 |website=www.tolweb.org |access-date=August 24, 2015 |archive-date=June 6, 2020 |archive-url= https://web.archive.org/web/20200606091921/http://tolweb.org/treehouses/?treehouse_id=3710 |url-status=live}}</ref> the pattern of [[encephalization]] started with ''Homo habilis'', whose {{convert|600|cm3|abbr=on}} brain was slightly larger than that of chimpanzees. This evolution continued in ''Homo erectus'' with {{convert|800–1,100|cm3|abbr=on}}, and reached a maximum in Neanderthals with {{convert|1200–1,900|cm3|abbr=on}}, larger even than modern ''Homo sapiens''. This brain increase manifested during postnatal [[neural development|brain growth]], far exceeding that of other apes ([[heterochrony]]). It also allowed for extended periods of [[Observational learning|social learning]] and [[language acquisition]] in juvenile humans, beginning as much as 2&nbsp;million years ago. Encephalization may be due to a dependency on calorie-dense, difficult-to-acquire food.<ref>{{Cite journal |last1=Kaplan |first1=Hillard |last2=Hill |first2=Kim |last3=Lancaster |first3=Jane |last4=Hurtado |first4=Magdelena |date=August 16, 2000 |title=A Theory of Human Life History Evolution: Diet, Intelligence, and Longevity |url= https://www.unm.edu/~hkaplan/KaplanHillLancasterHurtado_2000_LHEvolution.pdf |journal=Evolutionary Anthropology |volume=9 |issue=4 |pages=156–185 |doi=10.1002/1520-6505(2000)9:4<156::AID-EVAN5>3.0.CO;2-7 |s2cid=2363289 |access-date=September 20, 2019 |archive-date=February 15, 2020 |archive-url= https://web.archive.org/web/20200215120245/http://www.unm.edu/~hkaplan/KaplanHillLancasterHurtado_2000_LHEvolution.pdf |url-status=live}}</ref>

Furthermore, the changes in the structure of [[human brain]]s may be even more significant than the increase in size.<ref name="Park2007">{{cite journal |last1=Park |first1=M. S. |last2=Nguyen |first2=A. D. |last3=Aryan |first3=H. E. |last4=U |first4=H. S. |last5=Levy |first5=M. L. |last6=Semendeferi |first6=K. |date=March 2007 |title=Evolution of the human brain: Changing brain size and the fossil record |journal=[[Neurosurgery (journal)|Neurosurgery]] |volume=60 |issue=3 |pages=555–562 |issn=0148-396X |pmid=17327801 |s2cid=19610624 |doi=10.1227/01.NEU.0000249284.54137.32}}</ref><ref name="Bruner2007">{{cite journal |last=Bruner |first=Emiliano |date=December 2007 |title=Cranial shape and size variation in human evolution: Structural and functional perspectives |citeseerx=10.1.1.391.288 |journal=Child's Nervous System |volume=23 |issue=12 |pages=1357–1365 |doi=10.1007/s00381-007-0434-2 |issn=0256-7040 |pmid=17680251 |s2cid=16163137}}</ref><ref>{{cite journal |last=Potts |first=Richard |author-link=Rick Potts |date=October 2012 |title=Evolution and Environmental Change in Early Human Prehistory |journal=Annual Review of Anthropology |volume=41 |pages=151–167 |doi=10.1146/annurev-anthro-092611-145754 |issn=0084-6570}}</ref><ref name="Leonard_2007">{{cite journal |last1=Leonard |first1=William R. |last2=Snodgrass |first2=J. Josh |last3=Robertson |first3=Marcia L. |date=August 2007 |title=Effects of brain evolution on human nutrition and metabolism |journal=[[Annual Review of Nutrition]] |volume=27 |pages=311–327 |doi=10.1146/annurev.nutr.27.061406.093659 |issn=0199-9885 |pmid=17439362 |s2cid=18869516}}</ref> Fossilized skulls shows the brain size in early humans fell within the range of modern humans 300,000 years ago, but only got its present-day brain shape between 100,000 and 35,000 years ago.<ref>{{Cite journal |title=The evolution of modern human brain shape - Science |journal=Science Advances |date=January 5, 2018 |volume=4 |issue=1 |doi=10.1126/sciadv.aao5961 |last1=Neubauer |first1=Simon |last2=Hublin |first2=Jean-Jacques |last3=Gunz |first3=Philipp |pages=eaao5961 |pmid=29376123 |pmc=5783678 |bibcode=2018SciA....4.5961N}}</ref> [[File:Students explore hominid evolution.jpg|alt=Three students hold three different skulls in front of their faces, to show the difference in size and shape compared to the modern head|left|thumb|The size and shape of the skull changed over time. The leftmost, and largest, is a replica of a modern human skull.]] The [[temporal lobe]]s, which contain centers for language processing, have increased disproportionately, as has the [[prefrontal cortex]], which has been related to complex decision-making and moderating social behavior.<ref name="Schoeneman" /> Encephalization has been tied to increased starches<ref name="NYT-20150813">{{cite news |last=Zimmer |first=Carl |author-link=Carl Zimmer |date=August 13, 2015 |title=For Evolving Brains, a 'Paleo' Diet Full of Carbs |work=The New York Times |url= https://www.nytimes.com/2015/08/13/science/for-evolving-brains-a-paleo-diet-full-of-carbs.html |url-access=limited |access-date=August 14, 2015 |archive-url= https://ghostarchive.org/archive/20220101/https://www.nytimes.com/2015/08/13/science/for-evolving-brains-a-paleo-diet-full-of-carbs.html |archive-date=January 1, 2022}}{{cbignore}}</ref> and meat<ref>{{cite journal |last=Mann |first=Neil |date=September 2007 |title=Meat in the human diet: An anthropological perspective |journal=Nutrition & Dietetics |volume=64 |issue=Supplement 4 |pages=S102–S107 |doi=10.1111/j.1747-0080.2007.00194.x |issn=1747-0080 |doi-access=free}}</ref><ref>{{cite press release |last=McBroom |first=Patricia |date=June 14, 1999 |title=Meat-eating was essential for human evolution, says UC Berkeley anthropologist specializing in diet |location=Berkeley |publisher=[[University of California Press]] |url= http://www.berkeley.edu/news/media/releases/99legacy/6-14-1999a.html |access-date=April 25, 2015 |archive-date=April 20, 2015 |archive-url= https://web.archive.org/web/20150420060844/http://www.berkeley.edu/news/media/releases/99legacy/6-14-1999a.html |url-status=live}}</ref> in the diet, however a 2022 meta study called into question the role of meat.<ref>{{Cite journal |last1=Barr |first1=W. Andrew |last2=Pobiner |first2=Briana |last3=Rowan |first3=John |last4=Du |first4=Andrew |last5=Faith |first5=J. Tyler |date=February 1, 2022 |title=No sustained increase in zooarchaeological evidence for carnivory after the appearance of ''Homo erectus'' |journal=[[Proceedings of the National Academy of Sciences of the United States of America]] |volume=119 |issue=5 |doi=10.1073/pnas.2115540119 |doi-access=free |issn=0027-8424 |pmid=35074877 |pmc=8812535 |bibcode=2022PNAS..11915540B}}</ref> Other factors are the development of cooking,<ref name="Organ_2011">{{cite journal |last1=Organ |first1=Chris |last2=Nunn |first2=Charles L. |last3=Machanda |first3=Zarin |last4=Wrangham |first4=Richard W. |author4-link=Richard Wrangham |date=August 30, 2011 |title=Phylogenetic rate shifts in feeding time during the evolution of ''Homo'' |journal=[[Proceedings of the National Academy of Sciences of the United States of America]] |volume=108 |issue=35 |pages=14555–14559 |doi=10.1073/pnas.1107806108 |issn=0027-8424 |pmc=3167533 |pmid=21873223 |bibcode=2011PNAS..10814555O |doi-access=free}}</ref> and it has been proposed that intelligence increased as a response to an increased necessity for [[Dunbar's number|solving social problems]] as human society became more complex.<ref name="David-Barrett">{{cite journal |last1=David-Barrett |first1=T. |last2=Dunbar |first2=R. I. M. |date=2013 |title=Processing Power Limits Social Group Size: Computational Evidence for the Cognitive Costs of Sociality |journal=Proceedings of the Royal Society of London B: Biological Sciences |volume=280 |issue=1765 |page=20131151 |doi=10.1098/rspb.2013.1151 |pmid=23804623 |pmc=3712454}}</ref> Changes in skull morphology, such as smaller mandibles and mandible muscle attachments, allowed more room for the brain to grow.{{sfn|Bown|Rose|1987}}

The increase in volume of the [[neocortex]] also included a rapid increase in size of the [[cerebellum]]. Its function has traditionally been associated with balance and fine motor control, but more recently with [[speech]] and [[cognition]]. The great apes, including hominids, had a more pronounced cerebellum relative to the neocortex than other primates. It has been suggested that because of its function of sensory-motor control and learning complex muscular actions, the cerebellum may have underpinned human technological adaptations, including the preconditions of speech.<ref>{{cite journal |last1=Barton |first1=Robert A. |last2=Venditti |first2=Chris |date=October 20, 2014 |title=Rapid Evolution of the Cerebellum in Humans and Other Great Apes |journal=[[Current Biology]] |volume=24 |issue=20 |pages=2440–2444 |issn=0960-9822 |doi=10.1016/j.cub.2014.08.056 |pmid=25283776 |s2cid=5041106 |doi-access=free |bibcode=2014CBio...24.2440B}}</ref><ref>{{cite journal |last1=Starowicz-Filip |first1=Anna |last2=Milczarek |first2=Olga |last3=Kwiatkowski |first3=Stanisław |last4=Bętkowska-Korpała |first4=Barbara |last5=Prochwicz |first5=Katarzyna |date=2013 |title=Cerebellar cognitive affective syndrome CCAS – a case report |journal=Archives of Psychiatry and Psychotherapy |volume=15 |issue=3 |pages=57–64 |doi=10.12740/APP/18666 |doi-access=free}}</ref><ref>{{cite journal |last1=Yu |first1=Feng |last2=Jiang |first2=Qing-jun |last3=Sun |first3=Xi-yan |last4=Zhang |first4=Rong-wei |date=August 22, 2014 |title=A new case of complete primary cerebellar agenesis: Clinical and imaging findings in a living patient |journal=[[Brain (journal)|Brain]] |doi=10.1093/brain/awu239 |issn=1460-2156 |pmid=25149410 |volume=138 |issue=Pt 6 |pages=e353 |pmc=4614135}}</ref><ref>{{cite journal |last=Weaver |first=Anne H. |date=March 8, 2005 |title=Reciprocal evolution of the cerebellum and neocortex in fossil humans |journal=[[Proceedings of the National Academy of Sciences of the United States of America]] |volume=102 |issue=10 |pages=3576–3580 |doi=10.1073/pnas.0500692102 |issn=0027-8424 |pmc=553338 |pmid=15731345 |bibcode=2005PNAS..102.3576W |doi-access=free}}</ref>

The immediate survival advantage of encephalization is difficult to discern, as the major brain changes from ''Homo erectus'' to ''Homo heidelbergensis'' were not accompanied by major changes in technology. It has been suggested that the changes were mainly social and behavioural, including increased empathic abilities,<ref>{{cite book |last=Klein |first=Stefan |date=2014 |title=Survival of the Nicest |isbn=978-1-61519-090-4 |publisher=The Experiment}}</ref><ref>{{Cite journal |title=Social Network Size Affects Neural Circuits in Macaques |journal=[[Science (journal)|Science]] |date=November 4, 2011 |issn=0036-8075 |pmid=22053054 |pages=697–700 |volume=334 |issue=6056 |doi=10.1126/science.1210027 |last1=Sallet |first1=J. |last2=Mars |first2=R. B. |last3=Noonan |first3=M. P. |last4=Andersson |first4=J. L. |last5=O'Reilly |first5=J. K. |last6=Jbabdi |first6=S. |last7=Croxson |first7=P. L. |last8=Jenkinson |first8=M. |last9=Miller |first9=K. L. |bibcode=2011Sci...334..697S |s2cid=206536017}}</ref> increases in size of social groups,<ref name="David-Barrett" /><ref>{{cite journal |last1=Dunbar |first1=R. I. M. |date=1992 |title=Neocortex size as a constraint on group size in primates |journal=Journal of Human Evolution |volume=22 |issue=6 |pages=469–493 |doi=10.1016/0047-2484(92)90081-j |doi-access=free |bibcode=1992JHumE..22..469D}}</ref><ref>{{Cite journal |title=Encephalization is not a universal macroevolutionary phenomenon in mammals but is associated with sociality |journal=[[Proceedings of the National Academy of Sciences of the United States of America]] |date=December 14, 2010 |issn=0027-8424 |pmc=3003036 |pmid=21098277 |pages=21582–21586 |volume=107 |issue=50 |doi=10.1073/pnas.1005246107 |first1=Susanne |last1=Shultz |first2=Robin |last2=Dunbar |bibcode=2010PNAS..10721582S |doi-access=free}}</ref> and increased behavioral plasticity.<ref>{{Cite journal |last=Richard |first=Potts |date=1998 |title=Environmental Hypotheses of Hominin Evolution |journal=American Journal of Physical Anthropology |volume=107 |issue=S27 |pages=93–136 |doi=10.1002/(sici)1096-8644(1998)107:27+<93::aid-ajpa5>3.0.co;2-x |pmid=9881524}}</ref> Humans are unique in the ability to acquire information through social transmission and adapt that information.<ref>{{Cite book |last=Richerson |first=Peter J. |title=Not by Genes Alone: How Culture Transformed Human Evolution |date=2006 |publisher=[[University of Chicago Press]] |isbn=0-226-71212-5 |oclc=642503808}}</ref> The emerging field of [[cultural evolution]] studies human sociocultural change from an evolutionary perspective.<ref>{{Cite journal |last1=Mesoudi |first1=Alex |last2=Whiten |first2=Andrew |last3=Laland |first3=Kevin N. |date=August 2006 |title=Towards a unified science of cultural evolution |journal=Behavioral and Brain Sciences |volume=29 |issue=4 |pages=329–347 |doi=10.1017/s0140525x06009083 |pmid=17094820 |issn=0140-525X}}</ref>

[[File:Homo skull changes.png|center|thumb|750px|Evolution of the shape, size, and contours of the human (''Homo'') skull<ref>{{cite journal |last1=Berger |first1=L. R. |last2=Hawks |first2=J. |last3=Dirks |first3=P. H. |last4=Elliott |first4=M. |last5=Roberts |first5=E. M. |title=''Homo naledi'' and Pleistocene hominin evolution in subequatorial Africa |journal=eLife |volume=6 |date=May 9, 2017 |pmid=28483041 |pmc=5423770 |doi=10.7554/elife.24234 |doi-access=free}}</ref><ref>{{cite book |url= https://www.researchgate.net/publication/278682043 |title=Analyzing Hominin Hominin Phylogeny: Cladistic Approach |last1=Strait |first1=David |last2=Grine |first2=Frederick |last3=Fleagle |first3=John |name-list-style=vanc |date=2015 |isbn=978-3-642-39978-7 |pages=1989–2014 (cladogram p. 2006) |publisher=Springer}}.</ref><!--ref name="Saylor 2015 483–488" /-->{{efn|name=habilis|The conventional estimate on the age of ''H. habilis'' is at roughly 2.1 to 2.3 million years.{{sfn|Stringer|1994|p=242}}<ref>{{cite book |last1=Schrenk |first1=F. |last2=Kullmer |first2=O. |last3=Bromage |first3=T. |chapter=Chapter 9: The Earliest Putative ''Homo'' Fossils |editor1-last=Henke |editor1-first=W. |editor2-last=Tattersall |editor2-first=I. |title=Handbook of Paleoanthropology |date=2007 |pages=1611–1631 |doi=10.1007/978-3-540-33761-4_52}}</ref> Suggestions for pushing back the age to 2.8 Mya were made in 2015 based on the discovery of [[LD 350-1|a jawbone]].<ref>{{cite journal |last1=Spoor |first1=F. |last2=Gunz |first2=P. |last3=Neubauer |first3=S. |last4=Stelzer |first4=S. |last5=Scott |first5=N. |last6=Kwekason |first6=A. |last7=Dean |first7=M. C. |title=Reconstructed ''Homo habilis'' type OH 7 suggests deep-rooted species diversity in early ''Homo'' |journal=[[Nature (journal)|Nature]] |volume=519 |issue=7541 |pages=83–6 |date=March 2015 |pmid=25739632 |doi=10.1038/nature14224 |bibcode=2015Natur.519...83S |s2cid=4470282}}</ref>}}<ref>{{cite journal |last=Schuster |first=A. M. |date=1997 |title=Earliest Remains of Genus ''Homo'' |url= http://archive.archaeology.org/9701/newsbriefs/homo.html |journal=Archaeology |volume=50 |access-date=March 5, 2015 |number=1 |archive-date=March 17, 2015 |archive-url= https://web.archive.org/web/20150317002614/http://archive.archaeology.org/9701/newsbriefs/homo.html |url-status=live}} The line to the earliest members of ''Homo'' was derived from ''[[Australopithecus]]'', a genus which had separated from the Chimpanzee–human last common ancestor by late [[Miocene]] or early [[Pliocene]] times.
<!--Why is so much of the [[Chimpanzee–human last common ancestor]] article reproduced in this footnote?
with date estimates by several specialists ranging from  13 million years ago to more recently than six million years ago.
* {{cite journal |last1=Arnason |first1=U. |last2=Gullberg |first2=A. |last3=Janke |first3=A. |title=Molecular timing of primate divergences as estimated by two nonprimate calibration points |journal=Journal of Molecular Evolution |volume=47 |issue=6 |pages=718–27 |date=December 1998 |pmid=9847414 |doi=10.1007/PL00006431 |bibcode=1998JMolE..47..718A}}
* {{cite journal |last1=Patterson |first1=N. |last2=Richter |first2=D. J. |last3=Gnerre |first3=S. |last4=Lander |first4=E. S. |last5=Reich |first5=D. |title=Genetic evidence for complex speciation of humans and chimpanzees |journal=[[Nature (journal)|Nature]] |volume=441 |issue=7097 |pages=1103–1108 |date=June 2006 |pmid=16710306 |doi=10.1038/nature04789 |bibcode=2006Natur.441.1103P}}
* {{cite journal |last=Wakeley |first=J. |title=Complex speciation of humans and chimpanzees |journal=[[Nature (journal)|Nature]] |volume=452 |issue=7184 |pages=E3-4; discussion E4 |date=March 2008 |pmid=18337768 |doi=10.1038/nature06805 |bibcode=2008Natur.452....3W}}
"Patterson et al. suggest that the apparently short divergence time between humans and chimpanzees on the X chromosome is explained by a massive interspecific hybridization event in the ancestry of these two species. However, Patterson et al. do not statistically test their own null model of simple speciation before concluding that speciation was complex, and—even if the null model could be rejected—they do not consider other explanations of a short divergence time on the X chromosome. These include natural selection on the X chromosome in the common ancestor of humans and chimpanzees, changes in the ratio of male-to-female mutation rates over time, and less extreme versions of divergence with gene flow. I therefore believe that their claim of hybridization is unwarranted." see [[CHLCA#Current estimates|current estimates regarding complex speciation]].
--></ref>{{efn|''H. erectus'' in the narrow sense (the Asian species) was extinct by 140,000 years ago, ''[[Homo erectus soloensis]]'', found in [[Java (island)|Java]], is considered the latest known survival of ''H. erectus''. Formerly dated to as late as 50,000 to 40,000 years ago, a 2011 study pushed back the date of its extinction of ''H. e. soloensis'' to 143,000 years ago at the latest, more likely before 550,000 years ago.<ref>{{cite journal |last1=Indriati |first1=E. |last2=Swisher |first2=C. C. |last3=Lepre |first3=C. |last4=Quinn |first4=R. L. |last5=Suriyanto |first5=R. A. |last6=Hascaryo |first6=A. T. |last7=Grün |first7=R. |last8=Feibel |first8=C. S. |last9=Pobiner |first9=B. L. |last10=Aubert |first10=M. |last11=Lees |first11=W. |last12=Antón |first12=S. C. |display-authors=5 |title=The age of the 20 meter Solo River terrace, Java, Indonesia and the survival of ''Homo erectus'' in Asia |journal=[[PLoS One]] |volume=6 |issue=6 |pages=e21562 |date=2011 |pmid=21738710 |pmc=3126814 |doi=10.1371/journal.pone.0021562 |bibcode=2011PLoSO...621562I |doi-access=free}}{{collapsible list |title=Full list of authors |bullets=true |Etty Indriati |Carl C. Swisher III |Christopher Lepre |Rhonda L. Quinn |Rusyad A. Suriyanto |Agus T. Hascaryo |Rainer Grün |Craig S. Feibel |Briana L. Pobiner |Maxime Aubert |Wendy Lees |Susan C. Antón}}</ref>}}<ref name=":3">{{cite journal |last1=Mondal |first1=M. |last2=Bertranpetit |first2=J. |last3=Lao |first3=O. |title=Approximate Bayesian computation with deep learning supports a third archaic introgression in Asia and Oceania |journal=Nature Communications |volume=10 |issue=1 |page=246 |date=January 2019 |pmid=30651539 |pmc=6335398 |doi=10.1038/s41467-018-08089-7 |bibcode=2019NatCo..10..246M}}</ref><ref name="Zeitoun 2003 148–156">{{cite journal |last=Zeitoun |first=V. |title=High occurrence of a basicranial feature in ''Homo erectus'': Anatomical description of the preglenoid tubercle |journal=The Anatomical Record Part B: The New Anatomist |volume=274 |issue=1 |pages=148–56 |date=September 2003 |pmid=12964205 |doi=10.1002/ar.b.10028 |doi-access=free}}</ref><ref name="Proceedings 2015">{{cite journal |last1=Dembo |first1=M. |last2=Matzke |first2=N. J. |last3=Mooers |first3=A. Ø. |last4=Collard |first4=M. |title=Bayesian analysis of a morphological supermatrix sheds light on controversial fossil hominin relationships |journal=Proceedings. Biological Sciences |volume=282 |issue=1812 |page=20150943 |date=August 2015 |pmid=26202999 |pmc=4528516 |doi=10.1098/rspb.2015.0943}}</ref><ref name=":2">{{cite journal |last1=Dembo |first1=M. |last2=Radovčić |first2=D. |last3=Garvin |first3=H. M. |last4=Laird |first4=M. F. |last5=Schroeder |first5=L. |last6=Scott |first6=J. E. |last7=Brophy |first7=J. |last8=Ackermann |first8=R. R. |last9=Musiba |first9=C. M. |last10=de Ruiter |first10=D. J. |last11=Mooers |first11=A. Ø. |last12=Collard |first12=M. |display-authors=2 |title=The evolutionary relationships and age of ''Homo naledi'': An assessment using dated Bayesian phylogenetic methods |journal=Journal of Human Evolution |volume=97 |pages=17–26 |date=August 2016 |pmid=27457542 |doi=10.1016/j.jhevol.2016.04.008 |bibcode=2016JHumE..97...17D |hdl-access=free |hdl=2164/8796}}{{collapsible list |title=Full list of authors |bullets=true |Mana Dembo |Davorka Radovčić |Heather M. Garvinc |Myra F. Laird |Lauren Schroeder |Jill E. Scott |Juliet Brophy |Rebecca R. Ackermann |Chares M. Musiba |Darryl J. de Ruiter |Arne Ø. Mooers |Mark Collard}}</ref><ref>{{cite journal |last1=Mounier |first1=A. |last2=Caparros |first2=M. |date=2015 |title=The phylogenetic status of ''Homo heidelbergensis'' – a cladistic study of Middle Pleistocene hominins |journal=BMSAP |language=fr |volume=27 |issue=3–4 |pages=110–134 |doi=10.1007/s13219-015-0127-4 |s2cid=17449909 |issn=0037-8984}}</ref><ref name=":1" /><ref>{{cite book |url= https://books.google.com/books?id=bL2XDwAAQBAJ&q=Sahelanthropus+tchadensis&pg=PA7 |title=The Origins of Europeans and Their Pre-Historic Innovations from 6 Million to 10,000 BCE: From 6 Million to 10,000 BCE |last=Harrison |first=N. |date=May 1, 2019 |publisher=Algora Publishing |isbn=978-1-62894-379-5}}</ref><ref>{{cite journal |last1=Rogers |first1=A. R. |last2=Harris |first2=N. S. |last3=Achenbach |first3=A. A. |title=Neanderthal-Denisovan ancestors interbred with a distantly related hominin |journal=Science Advances |volume=6 |issue=8 |pages=eaay5483 |date=February 2020 |pmid=32128408 |pmc=7032934 |doi=10.1126/sciadv.aay5483 |doi-access=free |bibcode=2020SciA....6.5483R}}</ref>]]

=== Sexual dimorphism ===
The reduced degree of [[sexual dimorphism in humans]] is visible primarily in the reduction of the male [[canine tooth]] relative to other ape species (except gibbons) and reduced brow ridges and general robustness of males. Another important physiological change related to [[sexuality]] in humans was the evolution of [[Concealed ovulation|hidden estrus]]. Humans are the only hominoids in which the female is fertile year round and in which no special signals of fertility are produced by the body (such as genital swelling or overt changes in proceptivity during estrus).<ref>{{cite book |last=Tanner |first=Nancy Makepeace |title=On Becoming Human |url= https://books.google.com/books?id=_j45AAAAIAAJ |date=1981 |publisher=CUP Archive |isbn=978-0-521-28028-0 |page=[https://books.google.com/books?id=_j45AAAAIAAJ&pg=PA202 202]}}</ref>

Nonetheless, humans retain a degree of sexual dimorphism in the distribution of body hair and subcutaneous fat, and in the overall size, males being around 15% larger than females.<ref>{{Cite journal |last1=Reno |first1=Philip L. |last2=Lovejoy |first2=C. Owen |date=April 28, 2015 |title=From Lucy to Kadanuumuu: Balanced analyses of ''Australopithecus afarensis'' assemblages confirm only moderate skeletal dimorphism |journal=PeerJ |volume=3 |page=e925 |doi=10.7717/peerj.925 |pmid=25945314 |pmc=4419524 |issn=2167-8359 |doi-access=free}}</ref> These changes taken together have been interpreted as a result of an increased emphasis on [[pair bond]]ing as a possible solution to the requirement for increased parental investment due to the prolonged infancy of offspring.<ref>{{Cite journal |last=Lovejoy |first=C. Owen |date=October 2, 2009 |title=Reexamining Human Origins in Light of Ardipithecus ramidus |journal=[[Science (journal)|Science]] |volume=326 |issue=5949 |pages=74–74e8 |doi=10.1126/science.1175834 |issn=0036-8075 |bibcode=2009Sci...326...74L |url= http://doc.rero.ch/record/211449/files/PAL_E4439.pdf |pmid=19810200 |s2cid=42790876 |access-date=December 6, 2019 |archive-date=February 24, 2021 |archive-url= https://web.archive.org/web/20210224110943/http://doc.rero.ch/record/211449/files/PAL_E4439.pdf |url-status=live}}</ref>

=== Ulnar opposition ===
[[File:Erpurua eta hatz txikia.jpg|thumb|120px|Only the human is able to touch the little finger with the thumb.]]
The ulnar opposition—the contact between the thumb and the tip of the [[little finger]] of the same hand—is unique to the [[Homo|genus ''Homo'']],<ref>{{Cite journal |last=Young |first=Richard W. |date=January 2003 |title=Evolution of the human hand: The role of throwing and clubbing |journal=Journal of Anatomy |volume=202 |issue=1 |pages=165–174 |doi=10.1046/j.1469-7580.2003.00144.x |issn=0021-8782 |pmc=1571064 |pmid=12587931}}</ref> including Neanderthals, the [[Atapuerca Mountains|Sima de los Huesos]] [[Hominini|hominins]] and [[Homo sapiens|anatomically modern humans]].<ref name="Miriam">{{cite book |last=Ittyerah |first=Miriam |title=Hand Preference and Hand Ability: Evidence from studies in Haptic Cognition |publisher=[[John Benjamins Publishing]] |date=2013 |pages=37–38 |isbn=978-90-272-7164-8}}</ref><ref>{{cite web |last=Wilson |first=Frank R. |url= https://www.nytimes.com/books/first/w/wilson-hand.html |title=The Hand How Its Use Shapes the Brain, Language, and Human Culture |work=The New York Times |access-date=July 2, 2017 |archive-date=August 28, 2017 |archive-url= https://web.archive.org/web/20170828024550/http://www.nytimes.com/books/first/w/wilson-hand.html |url-status=live}}</ref> In other primates, the thumb is short and unable to touch the little finger.<ref name="Miriam" /> The ulnar opposition facilitates the precision grip and power grip of the human hand, underlying all the skilled manipulations.

=== Other changes ===
A number of other changes have also characterized the evolution of humans, among them an increased reliance on vision rather than smell (highly reduced [[olfactory bulb]]); a longer juvenile developmental period and higher infant dependency;<ref name="Kuzawa2014">{{cite journal |last1=Kuzawa |first1=Christopher W. |last2=Chugani |first2=Harry T. |last3=Grossman |first3=Lawrence I. |last4=Lipovich |first4=Leonard |last5=Muzik |first5=Otto |last6=Hof |first6=Patrick R. |last7=Wildman |first7=Derek E. |last8=Sherwood |first8=Chet C. |last9=Leonard |first9=William R. |last10=Lange |first10=Nicholas |date=August 25, 2014 |title=Metabolic costs and evolutionary implications of human brain development |journal=[[Proceedings of the National Academy of Sciences of the United States of America]] |volume=111 |issue=36 |pages=13010–13015 |doi=10.1073/pnas.1323099111 |pmid=25157149 |pmc=4246958 |bibcode=2014PNAS..11113010K |doi-access=free}}</ref> a smaller gut and small, misaligned teeth; faster basal metabolism;<ref name="Pontzer2016">{{Cite journal |last1=Pontzer |first1=Herman |last2=Brown |first2=Mary H. |last3=Raichlen |first3=David A. |last4=Dunsworth |first4=Holly |last5=Hare |first5=Brian |last6=Walker |first6=Kara |last7=Luke |first7=Amy |last8=Dugas |first8=Lara R. |last9=Durazo-Arvizu |first9=Ramon |last10=Schoeller |first10=Dale |last11=Plange-Rhule |first11=Jacob |last12=Bovet |first12=Pascal |last13=Forrester |first13=Terrence E. |last14=Lambert |first14=Estelle V. |last15=Thompson |first15=Melissa Emery |last16=Shumaker |first16=Robert W. |last17=Ross |first17=Stephen P. |date=May 4, 2016 |title=Metabolic acceleration and the evolution of human brain size and life history |journal=[[Nature (journal)|Nature]] |volume=533 |issue=7603 |pages=390–392 |bibcode=2016Natur.533..390P |doi=10.1038/nature17654 |pmid=27144364 |pmc=4942851}}</ref> loss of body hair;<ref name="MarkusJRantala2007">{{cite journal |last1=Rantala |first1=Markus J. |date=August 20, 2007 |title=Evolution of nakedness in ''Homo sapiens'' |url= https://zslpublications.onlinelibrary.wiley.com/doi/full/10.1111/j.1469-7998.2007.00295.x |journal=[[Journal of Zoology]] |volume=273 |issue=1 |pages=1–7 |doi=10.1111/j.1469-7998.2007.00295.x |access-date=November 5, 2022 |archive-date=November 5, 2022 |archive-url= https://web.archive.org/web/20221105183758/https://zslpublications.onlinelibrary.wiley.com/doi/full/10.1111/j.1469-7998.2007.00295.x |url-status=live}}</ref> an increase in
[[eccrine sweat gland]] density that is ten times higher than any other [[catarrhini]]an primates,<ref>[https://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1010614 Differential modularity of the mammalian Engrailed 1 enhancer network directs sweat gland development]</ref> yet humans use 30% to 50% less water per day compared to chimps and gorillas;<ref>[https://today.duke.edu/2021/03/humans-evolved-be-water-saving-ape Humans Evolved to Be the Water-Saving Ape | Duke Today]</ref> more [[Rapid eye movement sleep|REM sleep]] but less sleep in total;<ref>[https://www.smithsonianmag.com/science-nature/why-humans-sleep-less-than-their-primate-relatives-180980018/ Why Humans Sleep Less Than Their Primate Relatives]</ref> a change in the shape of the dental arcade from u-shaped to parabolic; development of a [[chin]] (found in ''Homo sapiens'' alone); [[Temporal styloid process|styloid processes]]; and a descended [[larynx]]. As the human hand and arms adapted to the making of tools and were used less for climbing, the shoulder blades changed too. As a side effect, it allowed human ancestors to throw objects with greater force, speed and accuracy.<ref>{{Cite web |last=Potter |first=Lisa Marie |title=Shouldering the Burden of Evolution |work=UCSF News Center |publisher=[[University of California San Francisco]] |date=September 8, 2015 |url= https://www.ucsf.edu/news/2015/09/131526/shouldering-burden-evolution |url-status=live |access-date=May 8, 2023 |archive-url= https://web.archive.org/web/20230508132136/https://www.ucsf.edu/news/2015/09/131526/shouldering-burden-evolution |archive-date=May 8, 2023}}</ref>