Editing Humanzee (section)

== Evidence for early hominin hybridization ==
{{main|Hominini|Chimpanzee–human last common ancestor}}
{{further|Archaic human admixture with modern humans }}

There is evidence for a complex speciation process  for the [[Chimpanzee–human last common ancestor|''Pan''–''Homo'' split]] which may include hybridization,<ref name="McCarthy-2008" /> or what is known as [[reticulate evolution]].<ref name="Caparros-2021" /><ref name="Arnold-2006" /><ref name="Winder-2014" /> Different chromosomes appear to have split at different times, suggesting that  large-scale hybridization  may have taken place over a period of as much as four million years leading up to the emergence of the distinct human and chimpanzee lineages as late as six million years ago.<ref name="complex">{{cite journal |vauthors=Patterson N, Richter DJ, Gnerre S, Lander ES, Reich D |title=Genetic evidence for complex speciation of humans and chimpanzees |journal=Nature |volume=441 |issue=7097 |pages=1103–8 |date=June 2006 |pmid=16710306 |doi=10.1038/nature04789 |bibcode = 2006Natur.441.1103P |s2cid=2325560 }}</ref>

The similarity of the [[X chromosome]] in humans and chimpanzees might suggest hybridization taking place as late as four million years ago. However, other mechanisms such as natural selection on the X chromosome in the chimpanzee–human last common ancestor may also explain the apparent short divergence time in the X chromosome.<ref>{{cite journal |author=Wakeley J |title=Complex speciation of humans and chimpanzees |journal=Nature |volume=452 |issue=7184 |pages=E3–4; discussion E4 |date=March 2008 |pmid=18337768 |doi=10.1038/nature06805 |bibcode = 2008Natur.452....3W |s2cid=4367089 }}
"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."
Wade, Nicholas. [https://www.nytimes.com/2006/05/18/science/18evolve.html?ex=1171515600&en=50ac61aa1c998951&ei=5070 "Two Splits Between Human and Chimp Lines Suggested"], ''The New York Times'', 18 May 2006. For a chromosomal homology map between these species see. {{cite journal|last=Pratas|first=D|author2=Silva, R|author3=Pinho, A|author4=Ferreira, P|title=An alignment-free method to find and visualise rearrangements between pairs of DNA sequences.|journal=Scientific Reports|date=May 18, 2015|volume=5|pmid=25984837|doi=10.1038/srep10203|page=10203|pmc=4434998|bibcode=2015NatSR...510203P}}</ref>

It is hypothesized that the peculiar features of ''[[Homo naledi]]'' may be due to them being descendants of a relatively recent hybridization event between ''Homo'' and ''[[Australopithecus]]''.<ref>{{cite journal |last1=Berger |first1=L.R. |author1-link=Lee Rogers Berger |last2=Hawks |first2=J.D. |author-link2=John D. Hawks |last3=Dirks |first3=P.H.G.M. |last4=Elliott |first4=M. |last5=Roberts |first5=E.M. |year=2017 |title=''Homo naledi'' and Pleistocene hominin evolution in subequatorial Africa |journal=[[eLife]] |volume=6 |doi=10.7554/eLife.24234 |pmid=28483041 |pmc=5423770 |doi-access=free }}</ref>