Editing Human evolution (section)

=== Divergence of the human clade from other great apes ===
[[File:016 Alpha male chimpanzee walking at Kibale forest National Park Photo by Giles Laurent.jpg|thumb|upright|Genetic data suggest that [[chimpanzee]]s and humans may have diverged from a common ancestor between 9 and 7 million years ago.<ref>{{cite news |title=Scientists observe chimpanzees using human-like warfare tactic |url=https://www.reuters.com/science/scientists-observe-chimpanzees-using-human-like-warfare-tactic-2023-11-02/ |work=Reuters |date=3 November 2023}}</ref>]]
Species close to the last common ancestor of gorillas, chimpanzees and humans may be represented by ''[[Nakalipithecus]]'' fossils found in Kenya and ''[[Ouranopithecus]]'' found in Greece. Molecular evidence suggests that between 8 and 4&nbsp;million years ago, first the gorillas, and then the chimpanzees (genus ''Pan'') split off from the line leading to the humans. Human DNA is approximately 98.4% identical to that of chimpanzees when comparing single nucleotide polymorphisms (see [[human evolutionary genetics]]). The fossil record, however, of gorillas and chimpanzees is limited; both poor preservation – rain forest soils tend to be acidic and dissolve bone – and [[sampling bias]] probably contribute to this problem.

Other hominins probably adapted to the drier environments outside the equatorial belt; and there they encountered antelope, hyenas, dogs, pigs, elephants, horses, and others. The equatorial belt contracted after about 8&nbsp;million years ago, and there is very little fossil evidence for the split—thought to have occurred around that time—of the hominin lineage from the lineages of gorillas and chimpanzees. The earliest fossils argued by some to belong to the human lineage are ''Sahelanthropus tchadensis'' (7 Ma) and ''Orrorin tugenensis'' (6 Ma), followed by ''Ardipithecus'' (5.5–4.4 Ma), with species ''Ar. kadabba'' and ''[[Ar. ramidus]]''.

It has been argued in a study of the life history of ''Ar. ramidus'' that the species provides evidence for a suite of anatomical and behavioral adaptations in very early hominins unlike any species of extant great ape.<ref name="aramidus">{{Cite journal |last1=Clark |first1=G. |last2=Henneberg |first2=M. |title=The life history of Ardipithecus ramidus: A heterochronic model of sexual and social maturation |journal=[[Anthropological Review]] |volume=78 |issue=2 |pages=109–132 |date=June 2015 |doi=10.1515/anre-2015-0009 |s2cid=54900467 |doi-access=free}}</ref> This study demonstrated affinities between the skull morphology of ''Ar. ramidus'' and that of infant and juvenile chimpanzees, suggesting the species evolved a juvenalised or [[paedomorphic]] craniofacial morphology via [[Heterochrony|heterochronic]] dissociation of growth trajectories. It was also argued that the species provides support for the notion that very early hominins, akin to bonobos (''Pan paniscus'') the less aggressive species of the genus ''Pan'', may have evolved via the process of [[self-domestication]]. Consequently, arguing against the so-called "chimpanzee referential model"<ref name="sayers" /> the authors suggest it is no longer tenable to use chimpanzee (''Pan troglodytes'') social and mating behaviors in models of early hominin social evolution. When commenting on the absence of aggressive canine morphology in ''Ar. ramidus'' and the implications this has for the evolution of hominin social psychology, they wrote:

{{blockquote|Of course ''Ar. ramidus'' differs significantly from bonobos, bonobos having retained a functional canine honing complex. However, the fact that ''Ar. ramidus'' shares with bonobos reduced sexual dimorphism, and a more paedomorphic form relative to chimpanzees, suggests that the developmental and social adaptations evident in bonobos may be of assistance in future reconstructions of early hominin social and sexual psychology. In fact the trend towards increased maternal care, female mate selection and self-domestication may have been stronger and more refined in ''Ar. ramidus'' than what we see in bonobos.{{r|aramidus|page1=128}}}}

The authors argue that many of the basic human adaptations evolved in the ancient forest and woodland ecosystems of late [[Miocene]] and early [[Pliocene]] Africa. Consequently, they argue that humans may not represent evolution from a chimpanzee-like ancestor as has traditionally been supposed. This suggests many modern human adaptations represent [[Phylogeny|phylogenetically]] deep traits and that the behavior and morphology of chimpanzees may have evolved subsequent to the split with the common ancestor they share with humans.