If you naturally wake up earlier in the morning, some very old genetic variants may be behind your sleep patterns. Humans’ internal circadian clocks might be partially influenced by genetic material left behind by extinct Neanderthals. The findings are described in a study published December 14 in Genome Biology and Evolution and provides a window into how the sleep cycles of Neanderthals differed from our earliest ancestors. Studies like this one could be a step towards a better understanding of how genetic material from extinct hominins affects modern humans.  Â
Our bodies respond to the environment
Modern Homo sapiens trace their origins back 300,000 years. Biological features in these early humans were shaped by environmental factors like sunlight or altitude. Roughly 70,000 years ago, the ancestors of modern Eurasian humans began to migrate out of Africa north towards Europe and Asia. Here, they experienced new environments and more seasonal variation in both temperatures and daylight.Â
[Related: Night owls can become early birds. Here’s how.]
“We also know from other species that live across broad ranges of latitude that their circadian clocks often adapt to the differences in light/dark cycles,” study co-author and University of California, San Francisco computational biologist Tony (John) Capra tells PopSci. “In particular, in higher latitudes there is more seasonal variation in light/dark cycles over the course of the year than in more equatorial latitudes.”
They also encountered different types of early hominins as they left Africa, including Denisovans and Neanderthals. The different environmental conditions on these northern continents meant that Neanderthals and Denisovans had different genetic variations from those coming out of Africa. When they began to interbreed with Neanderthals about 50,000 years ago, it created the potential for humans to get some of the genetic variants that were already adapted to…
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