Interesting Topics on Evolution

I'm finding those epigenetic papers a little technical and hard to wrap my head around. If that was my introduction to this subject, I don't think that I would have the passion for it that I do.

Part of evolutionary strategy: if you're past reproductive age, you don't warrant upkeep.

Altruism is considered a hallmark of the human species’ success, and it’s a well-documented developmental milestone. Kids start off highly selfish and remain that way through preschool, but at about age six they start to become a bit more generous. This pattern, however, has only been studied in relatively affluent kids living in relatively peaceful circumstances. It’s entirely unknown if children would continue to act altruistically in the face of adversity. Will the precocious altruism of childhood survive severe tribulation, or will kids revert back to their earlier self-centeredness? The Sichuan earthquake provided a natural “stress test” to examine the strength of youthful generosity.

Before the earthquake hit, the scientists had given 6- and 9-year-old a version of what’s called the Dictator Game—considered the gold standard for measuring altruism in the lab. Working individually with a researcher, each child is allowed to select stickers to keep. But then afterward, they are asked if they would like to give some of their own stickers to an anonymous classmate who is not playing the game—and therefore has no stickers. The children make their donations in a sealed envelope, so they believe that nobody knows how much, if anything, they are giving away.

But the scientists do know, and this group of kids fit the normal pattern. That is, 6- and 9-year-olds were not significantly different in their altruistic giving in the time before the earthquake. Then, one month after the earthquake, the scientists gave the same test to another, similar group of 6- and 9-year-olds. (They couldn’t follow up with the same children, because they could not locate many of them.) They wanted to see if the normal development of altruism was affected by the disaster experience, in either age group.

And it was, in an interesting way. The 9-year-olds actually gave much more—they were more generous—after the earthquake than before. The experience appeared to solidify and indeed enhance their altruism. But the younger kids gave significantly less than before the quake. The immediate effect of the disaster was to make the 6-year-olds more selfish. Put another way, their new-found altruism did not survive the earthquake.
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Three years after the earthquake, the kids’ altruistic giving returned to pre-quake levels, suggesting that the earlier changes were an acute response to the immediate aftermath of the disaster. In other words, the younger children opted for self-preservation in a crisis, suggesting that their emerging generosity is still fragile—but this reaction was not long-lasting. The altruism of the older children was apparently robust enough to withstand the challenge of adversity. Importantly, empathy for other victims was the pathway to generous action.

So then I got to thinking, I wonder how many children Ghengis Khan had after the age of, say, 55?

Demographic theory suggests that polygyny may occur because of a surplus of women that results from a high incidence of male warfare. However, polygyny occurs in many situations of relatively balanced gender ratios or even, as in the case of the Yanomamo, where males outnumber females. Accordingly, some men accumulate two or more wives only at the expense of others who never marry, or, much more usually, marry at a later age than women do. As such, the society becomes divided between young bachelors, who may remain single into their thirties and older polygynists. This arrangement may occur informally or may become a marked feature of the social structure. For example, in some South African societies, such as the Zulu, all young men in their twenties were organized into military “age regiments” and were not allowed to marry until their term of service ended. As we have already suggested, differences in marital age are also created by bride wealth requirements.

The social division between polygynists and bachelors points to another prevalent theory of polygyny, which is based on social stratification. In societies where men are not distinguished by differences in access to productive resources, such as land and capital, status distinctions are mainly attained and expressed through direct control over people. This goal is most obviously acheived through incorporating many women into one’s domestic group and expanding it by fathering a large number of children. A stratificational theory of polygyny also accounts for its greater incidence in comparison to polyandry, since men tend to occupy higher statuses than women in the majority of societies.