Biology subjects

David Comas

Publications and source records attributed to David Comas.

3 recordsLinked to original sources

bioRxiv2016

The genetic structure of the world’s first farmers

We report genome-wide ancient DNA from 44 ancient Near Easterners ranging in time between ~12,000-1,400 BCE, from Natufian hunter-gatherers to Bronze Age farmers. We show that the earliest populations of the Near East derived around half their ancestry from a Basal Eurasian lineage that had little if any Neanderthal admixture and that separated from other non-African lineages prior to their separation from each other. The first farmers of the southern Levant (Israel and Jordan) and Zagros Mountains (Iran) were strongly genetically differentiated, and each descended from local hunter-gatherers. By the time of the Bronze Age, these two populations and Anatolian-related farmers had mixed with each other and with the hunter-gatherers of Europe to drastically reduce genetic differentiation. The impact of the Near Eastern farmers extended beyond the Near East: farmers related to those of Anatolia spread westward into Europe; farmers related to those of the Levant spread southward into East Africa; farmers related to those from Iran spread northward into the Eurasian steppe; and people related to both the early farmers of Iran and to the pastoralists of the Eurasian steppe spread eastward into South Asia.

Genetics↗

bioRxiv2015

Tandem repeat variation in human and great ape populations and its impact on gene expression divergence

Tandem repeats (TR) are stretches of DNA that are highly variable in length and mutate rapidly, and thus an important source of genetic variation. This variation is highly informative for population and conservation genetics, and has also been associated with several pathological conditions and with gene expression regulation. However, genome-wide surveys of TR variation have been scarce due to the technical difficulties derived from short-read technology.\n\nHere, we explored the genome-wide diversity of TRs in a panel of 83 human and nonhuman great ape genomes, and their impact on gene expression evolution. We found that populations and species diversity patterns can be efficiently captured with short TRs (repeat unit length 1-5 base pairs) with potential applications in conservation genetics. We also examined the potential evolutionary role of TRs in gene expression differences between humans and primates by using 30,275 larger TRs (repeat unit length 2-50 base pairs). About one third of the 13,035 one-to-one orthologous genes contained TRs within 5 kilobase pairs of their transcription start site, and had higher expression divergence than genes without such TRs. The same observation held for genes with repeats in their 3 untranslated region, in introns, and in exons. Using our polymorphism data for the shortest TRs, we found that genes with polymorphic repeats in their promoters showed higher expression divergence in humans and chimpanzees compared to genes with fixed or no TRs in the promoters. Our findings highlight the potential contribution of TRs to recent human evolution through gene regulation.

Evolutionary Biology↗

bioRxiv2015

Genetic evidence for an origin of the Armenians from Bronze Age mixing of multiple populations

The Armenians are a culturally isolated population who historically inhabited a region in the Near East bounded by the Mediterranean and Black seas and the Caucasus, but remain underrepresented in genetic studies and have a complex history including a major geographic displacement during World War One. Here, we analyse genome-wide variation in 173 Armenians and compare them to 78 other worldwide populations. We find that Armenians form a distinctive cluster linking the Near East, Europe, and the Caucasus. We show that Armenian diversity can be explained by several mixtures of Eurasian populations that occurred between [~]3,000 and [~]2,000 BCE, a period characterized by major population migrations after the domestication of the horse, appearance of chariots, and the rise of advanced civilizations in the Near East. However, genetic signals of population mixture cease after [~]1,200 BCE when Bronze Age civilizations in the Eastern Mediterranean world suddenly and violently collapsed. Armenians have since remained isolated and genetic structure within the population developed [~]500 years ago when Armenia was divided between the Ottomans and the Safavid Empire in Iran. Finally, we show that Armenians have higher genetic affinity to Neolithic Europeans than other present-day Near Easterners, and that 29% of the Armenian ancestry may originate from an ancestral population best represented by Neolithic Europeans.

Genetics↗