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Comment by FlorinAndrei | Hacker News Reader

Well, the modern society is less like the savanna, which was the environment that shaped men throughout the evolutionary history of our species, and more like the cave, which was the environment that shaped women. Less physical confrontation, more squabbling. Less concrete, immediate dangers, more abstract worries. Less ass-kicking, more cooperation.

Heck, even spatial abilities are so last-century, now that everyone has a GPS.

So then you get things like men's constantly decreasing fertility, for decades now. Decreasing testosterone levels, again trending downwards for many years now.

I'm not saying this is either good or bad, I'm just saying this is an environment which creates different evolutionary pressures, and our species is responding to it.

I'm not sure I can imagine the destination, though.

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Half a century--two human generations--is not nearly enough time for evolutionary pressures to have the sort of effect you are talking about. Least of all in a society of abundance in which the majority of members reproduce.

Instead, I'd suggest you look at the various changing environmental factors for an explanation of these phenomena: BPA in plastics (http://en.wikipedia.org/wiki/Bisphenol_A), the growing use of soy in human diets (with its attendant phyto-estrogens), and the growing quantities of synthetic human estrogen in the environment (already known to have effects on fish, see for instance http://www.seattlepi.com/local/124939_estrogen04.html).

Sure, phyto- and xeno-estrogens are strong suspects in this case. But here's another data point:

Measure the testosterone level in your bloodstream.

Then for a few weeks start doing heavy squats (weight lifting) every other day, go car racing, skydiving, etc.

Now measure T again. See the difference?

There are all sorts of things like that. The bottom line is, the more secure the environment, the less the need for men to be "men".

Also, I was not implying that the new evolutionary pressures have already made changes, I was just saying the changes are being made now - but how long before they will become visible, I have no idea. Probably not tomorrow.

I agree that lack of physical activity is another likely factor for changing hormone levels and their secondary effects.

However, I know of no reason to think that these changes are heritable, or that naturally low T is actually a reproductive advantage in our society. (Indeed, given that we have inverted the more typical historical trend of the wealthy out-reproducing the less wealthy, and the selection of low-T for wealth here asserted, one might expect that this society actually reflects reproductive pressure against low-T, rather than in favor of it.)

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