Final piece in the puzzle: scientists complete the genome of the bonobo - the last great ape to be sequenced
An international team of scientists has successfully sequenced the genome of the bonobo (Pan paniscus), which is, along with the chimpanzee (Pan troglodytes), one of man's closest relatives.
Although they are similar in many respects, bonobos and chimpanzees differ from each other in striking ways and the study shows that 3% of the human genome is more closely related to either the bonobo or the chimpanzee genome than these are to each other.
The study, published in the journal Nature, brought together researchers from Austria, the Democratic Republic of Congo, Denmark, Germany, Italy, Japan, Kenya, Spain, Turkey, Uganda, the United Kingdom and the United States.
The sequencing was carried out by researchers at the Max Planck Institute for Evolutionary Anthropology in Germany and who were supported by the EU-funded TWOPAN ('Genomic and phenotypic evolution of bonobos, chimpanzees and humans') project. TWOPAN, which began in 2009 and runs until 2014, is funded to the tune of EUR 2,199,996 by a European Research Council (ERC) Advanced Grant, part of the 'Ideas' Theme of the EU's Seventh Framework Programme (FP7).
The study results shed light on the ancestry of the two ape species and might eventually help scientists understand the genetic basis of traits that humans share with one or the other ape species.
Scientists have long noted that to understand the extensive variation seen in gene expression within humans it is essential to know the extent of variation within closely related species. Therefore, before any assumptions can be made about how humans evolved, comparative data from both bonobos and chimpanzees are needed. The TWOPAN sequencers have completed the puzzle by sequencing the bonobo genome, the last great ape to remain unsequenced. As well as the chimpanzee, genome sequences have previously been generated from all other great apes, including the orang-utan and the gorilla.
While the lineage connecting humans to both the bonobo and chimpanzee split five to seven million years ago, the bonobo and chimpanzee lineages only split around one million years ago; despite such a recent divergence, the two ape species exhibit remarkable phenotypic differences: bonobos are known for their peaceful, playful and sexual behaviour that often involves same-sex partners, whereas chimpanzees are known for their aggressive nature.
Male chimpanzees use aggression to compete for dominance rank and obtain sex, and they cooperate to defend their home range and attack other groups. By contrast, bonobo males are commonly subordinate to females and do not compete intensely for dominance rank. They do not form alliances with one another and there is no evidence of lethal aggression between groups.
Despite the fact that on average the genomes of bonobos and chimpanzees are equally distant from the human genome, analysis of the genome sequence of the bonobo revealed that for some particular parts of the genome, humans are closer to bonobos than to chimpanzees, while in other regions the human genome is closer to chimpanzees. Further research is needed before any assumptions about which behavioral traits we can attribute to a particular ancestor are made.
Bonobo and chimpanzee territories in central Africa are close to one another and separated only by the Congo River. One theory for why they differ so much suggests that the formation of the Congo River 1.5-2.5 million years ago created a barrier to gene flow that allowed bonobos and chimpanzees to evolve different phenotypes over a relatively short time. Examination of the relationship between bonobos and chimpanzees showed that there appears to have been a clean split and no subsequent interbreeding, thus supporting this hypothesis.
The genome was sequenced from Ulindi, a female bonobo who lives at the Zoo Leipzig in Germany.
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Information Source: Max Planck Institute for Evolutionary Anthropology
Document Reference: Prufer, K., et al. 'The bonobo genome compared with the chimpanzee and human genomes', Nature, 2012. doi:10.1038/nature11128