What Happens When You Swap a Human Gene With a Neanderthal’s?

What are the key differences between modern humans and our closest relatives, the Neanderthals and Denisovans? For the Neanderthals, there doesn’t seem to be any sort of obvious difference. They used sophisticated tools, made art, and established themselves in some very harsh environments. But, as far as we can tell, their overall population was never […]