But it doesn't (and can't) determine which is cause and which is effect. Perhaps testosterone levels dropped as a consequence of agriculture and the rise of domesticated animals, if you don't have to hunt and kill your dinner every night, you don't need to be all that aggressive. To simply make the leap that humans suddenly became kinder and gentler through a spontaneous mutation is wishful thinking at best.
It's an interesting bit of information, but it reads like agenda driven science, and that ain't science at all.
You raise very interesting and pointed questions. I gather from the link that scientists know that the kinds of morphology that existed in human skeletons older that 50,000 years ago had features that testosterone creates and that their disappearance and appearance of modern type skulls and bones happen with less testosterone present, hence the theory that either testosterone decreased at that time or for other reasons had less effect. So one of those two things caused the other, the change in skull shape.
So there may be cause and effect there, but it was also at that time that human culture began to show lots of new innovations. The link between one and the other there is more theory and conjecture, I would agree.
I don't think agriculture is a viable counter argument, however, because I think that was more like ten thousand years ago, rather than fifty thousand. You can be less aggressive if you are smarter in catching your dinner too.
But given the nature of evolution, there is some survival benefit generally associated with what genes get passed on. The notion that survival of the fittest created a lot of early theorizing that man as killer ape explained our world dominance as a species but that has begun to come under question.
That notion has been replaced, I believe, with the notion that our success rests on cooperation. I am the one, I think, that put a political spin on that. It amuses me to call conservatives defensive and have them prove it. It is possible, however, that among the scientific community that favors the cooperation angle, there could be some liberal bias. I don't know. But I do think they make a good case.
Furthermore, with regard to conservative defensiveness, all the folk in this thread who favor the notion of aggression as the road to human success and poo poo the notions I suggest are just as humanly modern as I am, all members of the same liberal cooperative race as me. They are all metro-sexuals. Their defensive self hate is what makes them feel like they are being called primitive.

They are trying to defend a type of human that's been gone for 50,000 years.