In Science this week, a University of Washington-led group presents data showing that modern-day Melanesians carry genetic components passed down from Denisovans, a group of prehistoric hominins. The team analyzed the genomes of 1,523 individuals globally, including 35 individuals from Northern Island Melanesia in Papua New Guinea. They found that while all non-African populations studied inherited around 3 percent of their genomes from Neanderthals, Melanesians were the only population that also had significant Denisovan genetic ancestry, accounting for up to 3.4 percent of their genomes. The researchers mapped the genetic flow of Neandertal and Denisovan sequences, finding that Neanderthal admixture occurred at least three distinct times in modern human history, but Denisovan admixture probably only occurred once. Additional analyses suggest that certain regions of the modern human genome are particularly depleted of these archaic lineages, including those that play a role in the developing brain. GenomeWeb has more on this study here.
Also in Science, a team of European researchers publishes a report suggesting that a mother's microbiome influences the immune system of her child during gestation. They transiently colonized the guts of mice with a strain of E. coli and found that this infection, which resolved itself before birth, resulted in more innate lymphoid and mononuclear cells in the intestines of the offspring compared to mice born to microbe-free mothers. RNA analysis further showed that offspring born to gestation-only colonized mothers had greater expression of numerous genes — including those that influence cell division and differentiation, mucus and ion channels, and metabolism and immune function — compared with controls. The researchers speculate that maternal antibodies facilitate the transmission and retention of microbial molecules from mother to offspring.