Y-haplogroups and the «common ancestor»

[Luscinius]

Please explain the notion of the «common ancestor» as in following - «This man left Africa and is believed to be the common ancestor of all Eurasian and American populations.»

So he is the only man to have offspring or did he migrate alone? (sounds absurd). What is escaping my understanding?

[Chroma]

It would mean that all the males that were born outside of Africa were his descendants. This could mean many others, male and female, left along with him; and that these others also have descendants (containing genes from all the other chromosomes), but all Eurasians/North Americans (Non-Africans sounds less clunky) have a variant of his Y-chromosome.

Could someone please correct me if I'm wrong; he could be the ancestral 'Adam' of these Non-African populations and have never left Africa himself, right?

[JackBean]

Could someone please correct me if I'm wrong; he could be the ancestral 'Adam' of these Non-African populations and have never left Africa himself, right?

Actually, I think that this is the point He could be hardly the only man, who left Africa and either not only his descendants could survive...

[Chroma]

Not sure I understand what you mean... What I meant is this common-ancestor for all Eurasian and Americans, as determined by shared variants of his Y-Chromosome, was never required to leave Africa. He would still be the common ancestor to all Eurasian and American populations if all later successful migrations from Africa were by his descendants... Not necessarily likely, but just a possibility that the original posters statement seemed to overlook.

As far as other men migrating with him, I don't doubt this is the case, it would just be that their descendants never successfully copied their Y-Chromosome. All other genes are liable to come from any of the other individuals that left with him, as they would undoubtedly have also left descendants; just none of them had a successful male line.

[JackBean]

I think, that pretty much, what I meant