My bet is on the microplastics that have been found everywhere, from the arctic snow[1] down to the placenta of unborn babies[2]. They are known to be endocrine disruptors, however they only got their media spotlight (as far as I am aware) in the last ~4 years. Thus we're far away from being able to fully understand their effects on the human body.
Fun part is that I have some crazy (non-scietifically backed) theories that they are the cause of behavioral changes in humans which became more prominent in our society in the last 10-20 years. Unfortunately this is unresearched territory, as the only important article I came across were related to animals thus far [3][4]
I wonder how we can even determine what effects microplastics have on the human body when they are so prolific that every human on earth has them. Comparing with humans from the past has many challenges, so I guess the best we can do is comparing people that have more to those with less.
Maybe with longer lifespans, people making conscious choices which partner to have children with, and IVF being an option, there just isn't that much evolutionary pressure on sperm counts. Something that reduces your sperm count by 50% but makes you 10% more attractive could absolutely be an evolutionary advantage in the developed world.
Not that I think this is what's going on, but I think rejecting it outright is too hasty.
IVF and things like caesarians & other prenatal care are surely having an evolutionary effect. Fertility and ability to give healthy live birth used to be the most fundamentally important evolutionary pressures for us (and basically every other species), and now we can opt out of them.
IDK how long we'd expect it to take for most of humanity to become dependent on a high-tech society to reproduce, under those circumstances, but it'd seem really weird to me if that's not the direction we're going. But maybe that takes hundreds or thousands of years to have a pronounced effect, rather than tens.
From TFA: "But the transmission of these exposures doesn’t stop there—the epigenetic effects of these exposures may be transmitted from one generation to the next, not just from the mother but possibly from the father too. It may be due to factors in the father’s sperm that disrupt the reproductive development of male fetuses in the womb, Levine notes."
