For as long as i can remember i've been fascinated by How humans used to live and the social bonds between them. I've watched countless documentaries and read many articles on the Neaderthals and was just wondering something.

A species is often defined as a large group of organisms who can inerbreed and produce fertile offspring.

Why then do some Modern humans have traces of Neanderthal DNA  and Denisovan DNA? if they are a different species to us surely when we breed the offspring would be infertile? or does it work because we are very closely related species?

Also has science desided whether they are a subspecies of Homo Sapiens or theur own species entirely?

Thank you for your time and for answering these questions. Apologies if something similar has been posted in the past.

Sadly this is one of those cases where the taught definition isn't as strict, or well defined as implied. The species concept you refer to is only one of many, and it has some issues firstly among plants (many of which can hybridise readily), and secondly with close, or recently diverged groups. A 'species' is just a human construct - a label only. While Neanderthals and Denisovians were seperate groups (and, are in fact seperate morphospecies) they were apparently close enough to modern humans genetically to interbreed.

Take a look at our own guide here; … s-concepts

And also the wikipedia page highlights some of the complexities: … definition

Last edited by Peter Falkingham (3rd Dec 2014 09:00:45)