The history of great apes

Nature (2013) doi:10.1038/nature12228

Great ape genetic diversity and population history

Javier Prado-Martinez et al.

Most great ape genetic variation remains uncharacterized1, 2; however, its study is critical for understanding population history3, 4, 5, 6, recombination7, selection8 and susceptibility to disease9, 10. Here we sequence to high coverage a total of 79 wild- and captive-born individuals representing all six great ape species and seven subspecies and report 88.8 million single nucleotide polymorphisms. Our analysis provides support for genetically distinct populations within each species, signals of gene flow, and the split of common chimpanzees into two distinct groups: Nigeria–Cameroon/western and central/eastern populations. We find extensive inbreeding in almost all wild populations, with eastern gorillas being the most extreme. Inferred effective population sizes have varied radically over time in different lineages and this appears to have a profound effect on the genetic diversity at, or close to, genes in almost all species. We discover and assign 1,982 loss-of-function variants throughout the human and great ape lineages, determining that the rate of gene loss has not been different in the human branch compared to other internal branches in the great ape phylogeny. This comprehensive catalogue of great ape genome diversity provides a framework for understanding evolution and a resource for more effective management of wild and captive great ape populations.

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Cultured orangutans

The is a long-standing debate about the origins of human uniqueness. Specific human adaptations (such as the use of sophisticated tools, fire, clothing, ornaments, etc.) seem to have occurred at different times. What seems to be most human, however, is language and culture. Our species, it turns out, is not the only one to have culture, i.e., transmission of know-how via non-genetic means, but we are certainly awfully good at it, aided by our ability to communicate with language.

One camp thinks that there was one or more genetic mutations that turned us from apes to humans. According to that point of view, we are genetically special, and our complex language and culture was made possible by our genetic endowment.

An alternative view is that humans are not that special genetically, or that their adaptations took hold long before the emergence of fully modern behavior during the Upper Paleolithic. According to that view, one can think of humans as kindling that took the spark of culture by accident, long after it was ready to receive it. As an analogy, we can say that Upper Paleolithic brains probably had the capacity to go to the Moon, but did not have the culture for it yet: settled agriculture, science, and the industrial revolution were needed first.

I tend to the latter view myself. If a Neandertal or even Homo heidelbergensis child were raised in a modern society, they would no doubt be able to function in it, even if they weren't very bright or if they talked/moved/looked funny. The fact that these species never developed the complex cultures that modern humans did is not in itself evidence that they were innately incapable to produce them.

In any case, the comparison of the modern human/Neandertal genomes, in conjunction with developmental studies/studies of pathological variants may yet shed more light on whether modern humans do have, after all, genetic mutations that acted as the great enablers of their cultural efflorescence.

The new study frames the debate by establishing that one part of "being human", cultural transmission across the generations isn't "only human".

Culture in Humans and Apes Has the Same Evolutionary Roots

ScienceDaily (Oct. 20, 2011) — Culture is not a trait that is unique to humans. By studying orangutan populations, a team of researchers headed by anthropologist Michael Krützen from the University of Zurich has demonstrated that great apes also have the ability to learn socially and pass them down through a great many generations. The researchers provide the first evidence that culture in humans and great apes has the same evolutionary roots, thus answering the contentious question as to whether variation in behavioral patterns in orangutans are culturally driven, or caused by genetic factors and environmental influences.

Current Biology, 10.1016/j.cub.2011.09.017

Culture and Geographic Variation in Orangutan Behavior

Michael Krützen et al.

Although geographic variation in an organism's traits is often seen as a consequence of selection on locally adaptive genotypes accompanied by canalized development [1], developmental plasticity may also play a role [2,3], especially in behavior [4]. Behavioral plasticity includes both individual learning and social learning of local innovations (“culture”). Cultural plasticity is the undisputed and dominant explanation for geographic variation in human behavior. It has recently also been suggested to hold for various primates and birds [5], but this proposition has been met with widespread skepticism [6,7,8]. Here, we analyze parallel long-term studies documenting extensive geographic variation in behavioral ecology, social organization, and putative culture of orangutans [9] (genus Pongo). We show that genetic differences among orangutan populations explain only very little of the geographic variation in behavior, whereas environmental differences explain much more, highlighting the importance of developmental plasticity. Moreover, variation in putative cultural variants is explained by neither genetic nor environmental differences, corroborating the cultural interpretation. Thus, individual and cultural plasticity provide a plausible pathway toward local adaptation in long-lived organisms such as great apes and formed the evolutionary foundation upon which human culture was built.

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