Arm-chair Quarterback statement is about to follow - Better (different?) nutrition definitely plays a role (see disclaimer) but it also lead me to wonder if the issue affecting the Californian Condors could be a factor [See 1].
As apex predators they have elevated levels of endocrine-disrupting chemicals. Since we (humans) are also pretty much an apex predator across a wide range of species it is an almost certainly we have the same sorts of problems
It's a bit startling how quickly it seems to be advancing, though: this 2005 article is saying girls were becoming pubescent "between 9 and 10, roughly a year early". It's only taken a couple decades for that to have turned into "...mostly of girls who were developing breasts at 7 or 8 years old" and "as early as 6 and 7"
Puberty starts earlier than it used to *for girls*. Which surely points towards plastics and phytoestrogens in food as being the much more likely cause than improved nutrition or obesity which would affects both boys and girls equally.
We have known that certain plastics mimic estrogen in the body for well over 10 years now. BPA is banned for use in baby products in most western countries for this exact reason, but is still present in thermal receipts and the majority of food and drink cans.
I think you need to look at ‘low density’ and compare it to historical (Paleolithic) population density.
It must be a stress response, so even lower density areas feel some of the pressures of overpopulation (resource scarcity, etc).
And I really think that endocrine disrupting chemicals can’t be ignored (but I’m studying analysis of complex environmental samples for my PhD so I’m biased)
Count Down: How Our Modern World Is Threatening Sperm Counts, Altering Male and Female Reproductive Development, and Imperiling the Future of the Human Race
> you change what your species used to eat, you evolve into something else
That is definitely not how evolution works. First of all, evolution doesn't happen noticeably over one or two generations, which is the timeline we're talking about here. Secondly, show me how something affects fecundity or survival before we can even begin talking about its affect on evolution.
You seem confused. Random chance for what? Affecting what? If not survival or fecundity, what is it affecting? If an effect is completely random, it cannot drive evolution, because it is not a force for selection of particular traits over other traits. What are you talking about?
As apex predators they have elevated levels of endocrine-disrupting chemicals. Since we (humans) are also pretty much an apex predator across a wide range of species it is an almost certainly we have the same sorts of problems
[1] "A New Study has found contaminants that were banned decades ago are still imperilling critically endangered California condors" (https://newscenter.sdsu.edu/sdsu_newscenter/news_story.aspx?...)