https://brainerves.com/question/what-happened-between-human-and-neanderthals-40000-years-ago/ Lalasticlala

The disappearance of the Neanderthal population is an exciting subject — imagine a human group that has lived for thousands of years and is very well-adapted to its environment, and then disappears… For a long time, it was thought that Homo sapiens had simply killed the Neanderthals. Today, thanks to the results of genetic analysis, we know that the encounters between Neanderthals and sapiens were not always so cruel, and that interbreeding took place — even today’s humans have genes of Neanderthal origin.” Silvana Condemi

Traces of Neanderthal DNA show up in humans, what is responsible for this?

https://brainerves.com/question/neanderthals-gene-found-in-humans-did-humans-mated-with-them/