The most comprehensive study to date into the health effects of collagen supplements found benefits for skin health and significant relief from osteoarthritis symptoms – but no meaningful improvements in sports performance.

When Neanderthals and ancient modern humans interbred, the pairings were mostly between male Neanderthals and female humans. This finding helps explain why Neanderthal ancestry present in most humans is unevenly distributed. Anatomically modern humans carry low levels of Neanderthal ancestry, but it is not evenly shared. When the genomes of Neanderthals and modern humans are compared, striking gaps known as “Neanderthal deserts” are revealed. These are large stretches of DNA in modern humans where Neanderthal genetic contributions are unusually rare. Such deserts appear across several chromosomes and are especially prominent on the X chromosome. According to Alexander Platt and colleagues, this pattern can be explained in one of two ways: Neanderthal variants on the X chromosome were disadvantageous in modern humans and were gradually eliminated by natural selection, or early interbreeding could have occurred primarily between male Neanderthals and female modern humans, resulting in little Neanderthal X-chromosome DNA ever entering the human gene pool.

To resolve these competing theories, Platt et al. evaluated the fate of early modern human DNA that entered Neanderthal populations during an earlier episode of human-Neandertal interbreeding. By examining these Neanderthal genomes alongside genetic data from Specific sub-Saharan African populations that lack Neanderthal ancestry, the authors were able to trace patterns of ancient gene flow. Platt et al.’s analysis revealed a 62% relative excess of modern human ancestry in Neanderthal X chromosomes, suggesting that interbreeding was predominantly between male Neanderthals and female modern humans. Further modeling indicates that mate preference offers the simplest explanation for this sex bias than population migration alone, although the authors cannot exclude the possibility of demographic sex biases playing an important role. Furthermore, differential migration and mate preference may all have been at play simultaneously. Subsequent negative selection likely further reduced Neanderthal variants in functional X-linked regions.

Though previous research has shown that bird populations are declining across North America, a new study is the first to show that the pace of loss has picked up speed since the mid-1980s in three regions: the Midwest, California and Mid-Atlantic states. After these hotspots of accelerated bird decline were revealed, researchers looked for factors that could explain the difference in the rates of decline, examining climate measures and human activity-related data. A top predictor of where the accelerated abundance loss occurred became clear, overlapping with locations of agriculture intensity as indicated by the extent of cropland and the use of fertilizer and pesticides.

How ancient attraction shaped the human genome

Why do modern humans carry small amounts of Neanderthal DNA almost everywhere in their genome except on the X chromosome? A new study by Alexander Platt and Daniel Harris in the lab of geneticist Sarah Tishkoff suggests the answer lies in ancient attraction: long-standing mating preferences between male Neanderthals and female humans shaped which parts of the human genome endured and which disappeared, challenging the idea that human evolution was driven solely by survival of the fittest.