RE: Dumb & Dumberer: Why Are Human Brains Shrinking?
One of the main characteristics of domestication is reduced aggressiveness
herd animals don't need a lot of agressiveness. pack animals do. I wonder if there are studies contrasting the relative brain sizes.
Are humans pack animals, or herd animals?
Of the other reasons you have listed as possible factors, I like the Idiocracy take the most. We no longer say, "well let's leave Slow Joe to that bear chasing us". Then Slow Joe has kids and now we're all a little slower.
Finally, I would expect that almost all of these factors come into play at some level of contribution.
And to tell you the truth, survival of the species doesn't depend on IQ either, Whether we are pack animals or herd animals, it is the social organization of humans that lets us survive. Sure, the guys with outlier IQs advance the human race, but it's the people getting laid that perpetuate the race.
I hope this following link advances your discussion!
Why are people so stupid????? Honestly, why?
It is definitely a complex issue, and I suspect that the different theories all have some play in it like you say. If people today are any indication, a high IQ often means that procreation is lower compared to an average or below IQ individual.
Joe Rogan did a hilarious bit on dumb people having kids. I wish I could find that clip
The introduction to the movie Idiocracy is also pretty good.
But we are missing a trick in linking breeding to IQ. It is going to be the more aggressive males that procreate most successfully.
Kind of brings us full circle