Mailund on the Internet

John Hawks: Are orangutans our closest living relatives?

No

My answer would be “it depends” and “some places, yes”, but that answer is a bit more complex…

We’ve been working on the orangutan genome sequence the last year – the genome paper will probably be submitted in a few months and we have a few companion papers on our work on it – and we think we have evidence that some places in the genome humans are closer related to orangutans than chimps (our closest living relatives) and gorillas (our second closests).

So as species, no orangutans are not our closest living relatives – chimps and gorillas, in that order, are closer related to us – but the picture is slightly more complex than this if we look at individual nucleotides in our genome.

It has to do with gene trees vs species trees and so called incomplete lineage sorting.

It is well known that we are mainly closest related to chimps, but quite a large fraction of the genome we are actually closer related to the gorilla. Check e.g.

• Genomic Relationships and Speciation Times of Human, Chimpanzee, and Gorilla Inferred from a Coalescent Hidden Markov Model, Hobolth et al. 2007
• Estimation of Hominoid Ancestral Population Sizes under Bayesian Coalescent Models Incorporating Mutation Rate Variation and Sequencing Errors, Burgess and Yang 2008

We think we see the same for humans and orangutans, but to a much lesser degree of course.

Our paper is still in a rough draft, so I won’t say more about it here…

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181-178=+3