That is, unfortunately, a vast oversimplification. “Winning” can only be determined in hindsight. Sure, you may have more kids than me. But what if all your kids die in the coming Zombie Apocalypse, while my lone child rises up to become the leader of the resistance? Your genes lose. You can only trace “winners” by looking at who’s alive now; their lineage was a “winning” one, while anyone whose lineage has died out has “lost”.
To the extent that there is such a thing as winners and losers in evolution, anyway.
It seems to me that the more we evolved to be able to change our environment, the more pressure our environment would put on us to evolve. It’s possible that our urbanized ways have made subtle adaptations in us. So I could see the testosterone thing being true at least in theory. But it’s also possible that we’ve subconsciously adjusted our testosterone levels to adjust to urban environments. (If there has been any change at all, which I doubt.)
I was recently reading about an interesting example of something like this, and it blows my mind.
When a woman has sex, she’s typically filled with about 300 million sperm. The sperm will stay alive inside of her for about 5 days. But they don’t all die at once. The population gradually reduces over those days, during which she might conceive. Subconsciously, her partner remembers how long it has been since he last had sex with her, and if they have sex again within those 5 days, he will only produce enough sperm to top her off back to 300 million. If they have sex an hour later, he’s pretty much shooting blanks. Not because he’s run out, but because he knows that she’s full up. In fact, that’s why there’s a wet spot – she’s getting rid of the extras.
I don’t know that there’s any way to quantize the selection pressures we’re facing. All we can reasonably say is that the pressures may be “different”; there’s no way of telling if they are “more” or “less” than in the past.
Sounds like BS to me… I think some got their causality mixed up with pseudoscience.
Possibly, but I trust the scientific method behind it as well as the researcher. It wouldn’t be difficult to test. What could be done (and I believe was) is have a bunch of men have sex with their partners, somehow saving the ejaculate (I don’t know how, maybe in some rubbery containment system, perhaps ribbed for her pleasure), then have a bunch of research assistants count the sperm. A few days later, have half of them do it again and have the other half masturbate. Count the sperm again. Even better, have couples record their activities over the course of a year.
I just read an article in SciAm (either the January or February issue - I’m behind) claiming that, if anything, we are evolving more quickly now than before civilization. I don’t recall if rate of change was measured by gene changes per unit time, or physical trait changes per unit time, I would assume the former. Couldn’t the changes in fractions of types of gene changes be used as a proxy for changes in types of pressure? I suppose it is hard to determine the line between what is due to civilization, and what isn’t, but some changes clearly fall under the “wouldn’t have happened without civilzation” and some don’t, so a line could be drawn. For example, the ability for adults to consume milk has occurred in a few places, and only after the domestication of livestock, and according to that SciAm article, only in cultures reliant on the domestication of large enough animals to milk. Changes in pelvic shape would not be dependent on the existence of civilization. Increased rate of change in immunities would be civilization, or crowding at any rate, dependent, etc.
Man, you’ll really have to sell this to me, that I subconsciously (whatever that means) “remember” and accordingly adjust my seminal vesicle or testes or whatever. Are you saying that if I have sex with woman A one day, then sex with woman B the next, I will produce the same amount of sperm with each woman? But that if I have sex with woman A instead of woman B the next day, I’ll produce half as much?
I seem to remember a thread from a few years ago about dogs. The details I’ve retained are a little fuzzy, but basically:
Humans form communities.
Wolves move through those communities.
Lazy wolves stick around for the free scraps.
Lazy wolves evolve into dogs.
Not only do humans shape the evolution of dogs, but dogs shape the evolution of humans.
Therefore, human communities shape evolution of humans.
Okay, what if he jerks off? What if SHE jerks him off or orally stimulates him? Or if he has sex but with a condom, or if he has sex but pulls out and ejaculates on the sheets?
Unless you’ve misremembered, that is apparently the difference they’ve quantified (i.e., while using a condom):
It seems implausible that the man will “subconsciously” know how many sperm to produce to “fill up” his partner, while not “subconsciously” ignoring the conscious knowledge that he’s doing no such thing, given that his sperm are being collected instead.
The problem is that it comes back to the issue that spawned this very thread: which, if any, of those changes are adaptive? You’d need to answer that before you can begin to identify selective pressures, and increases or decreases thereof. We could all live in a radioactive zone, and that would certainly produce more net genetic mutations, but it doesn’t necessarily mean that selective pressures have increased.
Yet there’s still an awful lot of theoretical territory between “quantifiable difference” and “therefore, subconsciously adjusting the amount of sperm in one’s ejaculate to maintain a near-steady sperm volume over time in the female”. It’s not that it occurs that’s troublesome, it’s the conclusion for why.
Subconscious may be the wrong word. If it’s some kind of autonomic/pheromonal reaction, it may be more glandular than neurologic and therefore completely divorced from what he knows or doesn’t know.
Likewise, I don’t plan how much bile my liver makes. It responds to what I’ve been eating lately. I may know that I’m eating a 12 oz. block of cream cheese, but if I’ve been eating veggies for the last month, when my* gall bladder senses the fat and squeezes, there may not be enough bile to digest the whole block. There are nerves involved in the process, but they’re not attached to my thinking.
*only mine for literary purposes. My personal gall bladder is long gone. I also don’t eat blocks of cream cheese.
