> How much validity is there in positing the evolution of different contemporary human subgroups when these change at a fairly rapid rate and intermingle quite readily?
The article doesn't suggest that subgroups have evolved, rather that we have evolved to produce offspring sooner and faster in response to harsh conditions.
(So basically what you write in the rest of your post agrees with the article. I think!)
Do we even need to hypothesize this as a specialized evolutionary response?
“My life sucks; studying hard and looking for a job will not make it suck less, because even if I get good grades, nobody will hire me; however, if I have a baby, then there will at least be something cute in my immediate environment that loves me” looks like a straightforward chain of logical reasoning to me.
If there is a shortage of viable fathers in the local community, then having a baby will frequently lead to preferential financial and housing outcomes. More benefits, and a much better chance of getting social housing.
There's very little way to get out of this cycle, besides either creating a lot of jobs, sufficient that men become useful, or simply increasing peoples' benefits such that strategies like having babies no longer get you a better outcome.
Snarky response is that we don't need hypothesises at all anymore, we understand enough of the universe to be rather ok.
But there is value in accepting this theory, which I might add is reasonably well accepted as far as most other mammals. The value is that your chain of logic blames first the people themselves, and feeds back into the aticle's final justification, that is, while such things as increasing education are politically expedient, they don't actually change conditions. Getting this theory widely accepted can do a great deal for changing how governments fight the problems of poverty.
> we have evolved to produce offspring sooner and faster in response to harsh conditions.
One could also understand the article the other way around: We have evolved to reproduce in response to natural conditions, and one result is women being able to get pregnant at about 15. Now, why should something like this happen if the natural 'optimum' would be rather 20 or 25?
Read this way, the fact that needs an explanation is women getting pregnant rather late.
The article doesn't suggest that subgroups have evolved, rather that we have evolved to produce offspring sooner and faster in response to harsh conditions.
(So basically what you write in the rest of your post agrees with the article. I think!)