There's a tendency to distill humans into subspecies, at least for storytelling purposes. We have the more dog like, the dwarf like, the geek like... the elvyn like. Every Middle Earth has its lore and its peoples, its nations, its guilds & ethnicities.
Astrological birth signs brought some order to the scene. Personality types -- people are big into measuring those.
Not everyone wants to be a goth (and you don't have to be one to love one).
In terms of our shared genome providing needed plasticity, adaptability, I'd say the record proves we're well endowed. That doesn't make us masochistic however. Let's not invite stupid outcomes. Let us not "just see what it's like" to survive another nuclear holocaust how about it?
Keith talked about a new Van Allen Belt thanks to nuclear testing. In sweeping the web, I see lots of caveats and denials. It's gone now they say. Some people got angry about those tests and I can see why: those testers don't own the world, merely act like they do (= bad acting). That level of hubris is ugly to behold.
I can see some of those races people believe in. They're less transient than cloud formations certainly. Others I don't see or am less likely to want to believe in. I'll suspend my disbelief, but only by so much. Call me a skeptic.
Yes, I believe the lunar landings (Apollo) really happened.
Once we start arguing who is racially "pure" (archetypal) versus who is "mixed" (mongrel) I tend to walk away, unless we're talking about breeds of horse or dog maybe (seems harmless enough).
I don't trust the judging or judges where humans are concerned. They start making it matter, make it more than a show. Yet there's no "racial essence" in the DNA anywhere. Pigeon holing, or coming up with percents ("the mix"), is a nightmare, a quagmire, and an exercise in futility sometimes. Pseudo-science takes over, pandering to some "master race" mythology.
There is such a thing as taking racial categories too seriously, kind of how I felt about the WTO. I liked it when Yes Men poked holes. Not every story has the same half life, just like not every open source project achieves critical mass or long term momentum.