Analyzing genomes from 300 individuals from 142 populations, an international team of scientists has produced an unprecedentedly high-resolution picture of human diversity. With the data, the scientists identified previously unknown features of human genome variation, including a difference in the rate at which non-Africans and Africans have accumulated mutations.
“We detect slightly more new mutations in non-Africans,” says David Reich, a geneticist at Harvard Medical School and the Howard Hughes Medical Institute who led the project. Reich says one of several possible explanations for this finding is that the average age of reproduction among non-Africans has been different from that of Africans over the last 50,000 years.
Analysis of the diverse set of genomes also showed that all populations of modern humans found outside of Africa stem from a single ancestral African population. The data also suggest that the evolution of tool making, hunting, ornamentation and other cultural activities were probably not driven by changes to a single neuronal gene or even a handful of them. “The idea that one or a few genetic changes are responsible for the great changes in human behavior documented in the archaeological record around 50,000 years ago is not consistent with our data,” Reich says. Instead, these rapid transformations in the behavior of modern humans were probably driven by cultural innovations or exposure to new environments, Reich and his colleagues write in their report, published Sept. 21 in Nature.
The report is the third major analysis of data from the Simons Genome Diversity Project, which consists of high-resolution human genome sequences spanning a wide range of human populations. The dataset was released to the research community in 2014 and has been requested by researchers around the world. Previous papers on the dataset studied the duplication and deletion of human copy number variants and the contribution of archaic humans (Neandertals and Denisovans) to present-day genomes.
Reich is particularly interested in analyzing the dataset together with sequences of ancient DNA to study variation in the human genome at different time points. “With time series data, it is possible to track natural selection as it happened over time,” he says. “The Simons Genome Diversity Project is such an extraordinary dataset, far beyond anything we had access to before. But with the advances in ancient DNA technology, we can now realistically imagine carrying out a similarly comprehensive genome sequencing study from the deep past.”