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Genetics
Regions of the human genome that evolved rapidly after the separation between hominins and chimpanzees have now been charted. They contain genomic elements that are unique to humans and are linked to neurodevelopment and disease.
What are the genetic changes that separate humans from chimpanzees? The discovery that there is little difference between these species in terms of protein-coding DNA sequences has led to the hypothesis that the genomic changes responsible for human-specific traits are mainly evident in the non-protein-coding region of the genome1. Writing in Celt, Ma ngan et at.2 report that the most rapidly evolving of these non-coding regions are related to human-specific neurodevelopment and disease. The work provides insights into how we differ from our great-ape ancestors.
So far, most studies of human-specific evolution have examined either coding DNA or non-coding regions that are highly evolutionarily conserved in all vertebrates, but mutated at a faster rate in humans than in other species3. These genetic sequences, named human accelerated regions (HARs), mostly reflect existing regulatory elements in DNA that have evolved more rapidly in humans4,5. However, highly conserved regions make up only about 5% of the human genome4.
Mangan et al. took a broader view, looking at the entire genome, which consists largely of non-conserved regions, to identify sequences that have undergone human-specific evolution. They aligned all great-ape and human genome sequences to computationally infer the genome of the last common ancestor of humans and chimpanzees. By comparing the modern human genome with that of the human-chimpanzee ancestor, they identified rapidly diverging sequences, which they dub human ancestor quickly evolved regions (HAQERs).
The authors identified 1,581 HAQERs, which were heavily mutated in humans compared with other species. They found that HAQERs had undergone more genetic changes in a given timeframe than had HARs, making them the fastest-evolved regions in the human genome. Furthermore, there were only 6...