I can always tell when spring arrives because that's when nubile girls who are ovulating start pumping out their distinctive scent. Apparently only a small fraction of guys can detect this, in the same way that some people have super-sensitive tastebuds, and in the way that some people see colors well while others are color-blind.
It's even easier to tell because at '80s night there are perhaps 100 girls, all college-age, and if even a good fraction of them are ovulating, it knocks me over like a tidal wave when I'm walking up the stairs. However, last week I detected one girl in heat -- confirmed by her behavior in the dance cages -- even though it was still winter. Still, it had warmed up a fair amount since the dead-of-winter temperatures -- freezing, but not in the teens or 20s like it was before.
This made me realize that there must be differences between individual girls in how soon they come out from winter hibernation and get down to the business of looking for a mate and making babies. There's a trade-off: if she's highly sensitive, she will go into mating mode at even slight hints that the season has begun, so she'll never get a late start, although she'll occasionally come out too early (false alarm) and be left out in the cold. If she's hardly sensitive at all, she'll only come out when it's beyond a shadow of a doubt that mating season has begun, so she'll never be in mating mode too early and with little to do, but she'll occasionally remain in hibernation when she should be out and about.
There's no single best strategy to resolve this trade-off -- the more you try to eliminate one type of error, like the mistake of coming out too early and having little to do, you automatically suffer the other type of error, like sleeping in too late when there's plenty for you to be doing. So, a range of strategies will evolve and persist, rather than the single best strategy out-breeding all the others.
It follows as a prediction that females who are the most sexualized -- who lose their virginity earlier, have their first kid earlier, have more partners, have sex and kids outside of wedlock, etc. -- will be the early birds, while the least sexualized will be the stragglers. The most sexualized ones are really worried about sleeping through the party once mating season has begun, so they'll take the risk of going into mating mode too early. The least sexualized ones are more worried choosing the wrong partner, not having a great environment to conceive the baby in, and so on, from jumping the gun, so they'll take the risk of having their uteruses running idle when they could be put to good use.
And sure enough, that's just what we see. Here is a relevant WSJ article; skip to the chart at the very bottom. Mothers who give birth in January are the least likely to be married, the most likely to be teenagers, and the least educated, whereas mothers who give birth in May are the mirror image. Rewinding back to conception, that means the most sexualized mothers conceived in April, which leaves only 10 to 40 days after the beginning of spring for them to get into mating mode. The least sexualized mothers conceive in August, fully four months later -- talk about sleeping through the party! -- when there is no doubt left that mating season has begun and while the weather is still warm enough before the cooling of autumn.
This doesn't mean that the most sexualized mothers took only 10 to 40 days to find a stranger to mate with. They could have already been with someone for years. The point is even if they've been with someone that long, when during the year that they choose to have a kid do they go into baby-making mode? Damn early.
I wonder if colleges that have more lower-status students have earlier spring breaks than ones with more higher-status students?