P1na: Common ancestors would typically mean common physical traits, though. That's what genetics are about, are they not? People who have dark skin, thick lips and tight wiry hair will have children with those same traits, and when a big enough number of people share those traits, specially when they share geographic ancestry, I feel it's fair to call that a race. The distinction may be fuzzy at times, and less clear cut than in tose species which had strict selective breeding for centuries (such as horses or dogs), but it's there. Generalizations aren't true 100% of the time, far from it, but we are statistically likely to fall into quite a few of the characteristics atributed to the groups we belong to.
I don't know, I feel like we all agree deep down and we're just arguing semantics. I don't think there's a "black gene" or a "white gene", which you either inherit or don't. It's murkier than that, but it is still there. Which physical traits you are born with is down to genetics, and the race you belong to depends on those traits; even if the link of which traits belong to which races is mostly social. I'm not talking superior nor inferior, just different. And difference is good IMO, it makes it worth going out and seeking new things.
But it is an irrelevant and as meaningless a difference as a "race" of hairy bald people or a race of fat people (I think you were in fact the one that made this comparison before?). There are dark-skinned, thick-lipped, wirey haired people who aren't african or "black", there are fair skinned, light-haired people who aren't "white", and these aren't just exceptions to a generality.
It gets even more confusing when terms like "asian" are used, because it just means a continent, one which has a huge variety of vastly different looking people.
Taking for example something I'm more familiar with, here are some examples of the "common physical traits" of pathans (probably unfortunately most famous outside of South Asia for making up the major component of what is known as the Taliban), a Pakistani/Afghani group that some Pakistanis might even call or treat as a "race", since they share common ancestors and geography:
Imran Khan,
Aftab Ahmad Sherpao,
Sharbat Gula,
Yusuf Pathan,
Some guy,
Some model All of these people share common ancestors, a common geography, but not so much physical traits. Are they the same race? Are one of them "asian" and one of them "white" and one of them "black"? To compound the hilarity and confusion, Pathans also share "genetic heritage" with jewish populations. Does that make them semite?
This is what I meant when I said that race is a societal construct, rather than genetic.