But this brings up an entirely different but parallel question, about context.

In my view, western toddlers are living in a state of great discordance between pretty much any hypothetical “EEA” and their actual surroundings. Even if one postulated (this would be wrong, but that won’t stop people from thinking it) that we evolved to be repulsed by natural poison things (berries, other plant product, etc.) we live in an environment where the poisons are found in attractive bottles with happy people (or Mr. Clean) depicted on them. I once helped rescue a kid who had eaten an entire bottle of blood pressure pills. He lived (it was close) but what he did was fairly logical. Bright blue, pretty, sugar coated. Of course he ate a bottle of them.

On the one hand, you have young children in rural parts of Africa left to look after precious resources like the family’s flock and allowed – expected – to handle fearsomely sharp knives.

Then you have mid-20th century Western countries, where children discovered that knives were tools just before puberty and spent all their time making models of things.

Then you have contemporary Western cultures, where from puberty up until the birth of the first child (sometimes beyond, if the country has a good welfare system), they indulge in tombstoning, experimenting with drugs, gang warfare (including terrorism, of course) and so on.

Then you have BDSMers, up to half of whom never stop trying to kill themselves….

I’d say getting into a good school has an inverse relationship with reproductive fitness.

Hence less and less of us are paying tax, while more and more of them are living off welfare and breeding like rabbits.

So, a test of this theory could be to see if, under controlled circumstances, children with younger siblings engage in more risky behavior than do only children of the same age.

So, why are toddlers always trying to kill themselves and when does it stop?

It stops when toddlers are no longer toddlers. The propensity to stick dangerous things into their mouths may continue well into adulthood although it seems to reach a peak during the 18-24 year old stage (think alcohol consumption). After that, it tends to decline because 1) they’ve been successful in killing themselves, and 2) they mature and realize pickling themselves on a regular basis isn’t really all that fun, never was, and the only reason they did it was because everyone else they associated with was also doing it—and tv commercials, university culture all make it seem like the thing to do. And all the sheeple said “baahhhhhhh”.

Snark aside, interesting ideas by Trivers–not sure how well they play out aside from selected examples. Still, intriguing possibilities there.