As more details emerge from the genomes of humans1,2, our closest living relatives the apes3,4 and our closest extinct relative the Neandertal, it will become possible to say what defines us as a species from a genetic point of view. Detailed studies of genes that carry human-specific evolutionary traits should reveal which ones have been especially important during human evolution. Ultimately, these efforts could uncover the biology beneath human cognition, language and culture, and might improve our understanding of conditions such as autism, schizophrenia and language impairments.
The common chimpanzee and the bonobo or pygmy chimpanzee are our closest living relatives, with whom we share a common ancestor that lived 5–7 million years ago. Humans and chimpanzees share a common ancestor with gorillas — the other major species of African apes — that lived 6–8 million years ago, whereas the common ancestor shared with the Asian orangutans lived 12–16 million years ago (Fig. 1).
Many species that were more closely-related to humans have lived and become extinct since the time of the chimpanzee- human ancestor. They are collectively called hominins. One hominin is the Neandertal, whose lineage diverged from ours 300,000–500,000 years ago. Neandertals lived in western Eurasia, sometimes alongside our ancestors, until they became extinct around 30,000 years ago.
Our technical ability to sequence genomes is improving rapidly and the cost is continually dropping. Soon it will be possible to sequence mammalian genomes accurately and cheaply in a matter of days. At the same time, technologies that allow high-speed surveys of proteomes and metabolomes — that is, all the proteins and metabolic molecules present in a tissue or cell — are also being developed.
Today, the most complete primate genome available is that of the human; the genomes of the chimpanzee, gorilla, orangutan and rhesus macaque are of lower and variable quality.
This year, a group of researchers published the first draft of the complete Neandertal genome5. Studying these genomes will help researchers identify the millions of nucleotide changes, and tens of thousands of insertions, deletions and duplications of short stretches of DNA, that have occurred since the divergence of modern humans from chimpanzees and, more recently, from the Neandertals.