English scientists say that Neanderthal and modern humans interacted beginning about 50,000 years ago and did so for about 20,000 years before Neanderthal went extinct. They believe the species interacted for about 5,400 years in Europe before Neanderthal went extinct. Per the article:
Neanderthals and Homo sapiens were both living in Europe at the same time for around 5,400 years, according to a new study that has many other implications. For starters, it’s now possible that Neanderthals and our species mated and otherwise interacted for some 20,000 years. “Significant interbreeding between Neanderthals and early modern humans had probably already occurred in Asia more than 50,000 years ago, so the dating evidence now indicates that the two populations could have been in some kind of contact with each other for up to 20,000 years, first in Asia then later in Europe,” Chris Stringer, research leader in Human Origins at the Natural History Museum in London, explained.
The study has been published in the latest edition of the journal, Nature.
It's possible that Neanderthals and other hominids that coexisted with humans, are the source of our legends of dwarves, trolls, ape-men, etc. From the book How to Think Like a Neanderthal.
At one time we did share the earth with humanlike but not human creatures!
But the Neanderthals went extinct at least 24,000 years ago - that's a hell of a long time for myths to last.
It seems like one of the great unrecognized tragedies of humanity, that the other hominids on the earth went extinct. Just think how much it would mean to us, if we could see another species of human around us.
They wouldn't be a different as intelligent aliens, but they would give us a sorely lacking perspective on our own thinking.