Caspari and Lee found a five-fold increase [in] the number of individuals surviving into old age in the Early Upper Palaeolithic period - around 30,000 years ago. This coincides with an explosive population growth of modern humans and the spread of archaeological artefacts that suggest the development of more complex social organisation.
...
Anthropologists have long suspected that older people may have played an important role in the development of early human societies by providing extra care for children, helping to accumulate useful information and strengthening kinship bonds.

The so-called "grandmother hypothesis", based on studies of African hunter-gatherer groups, suggests that infertile women are vital for successful child-rearing despite being unable to produce children themselves.

One of the biggest moral bombshells handed to Billy by the Tralfamadorians, incidentally had to do with sex on Earth. They said their flying-saucer crews had identified no fewer than seven sexes on Earth, each essential to reproduction. Again: Billy couldn't possibly imagine what five of those even sexes had to do with the making of a baby, since they were sexually active only in the fourth dimension.

The Tralfamadorians tried to give Billy clues that would help him imagine sex in the invisible dimension. They told him that there could be no Earthling babies without male homosexuals. They could be babies without female homosexuals. There couldn't be babies without women over sixty-five years old. They could be babies without men over sixty-five. There couldn't be babies without other babies who had lived an hour or less after birth. And so on.

It was gibberish to Billy.

# posted by Gerry Canavan @ 8:52 PM  |