I picked up Elaine Morgan’s The Descent of the Child and devoured it in an evening.  I liked it a lot, and Morgan is very readable, and yet I have to throw on a steaming pile of caveats.

That’s because she’s a promoter of the Aquatic Ape Hypothesis– the idea that humans went through an aquatic or near-aquatic stage that accounts for their many differences from the other apes, such as hairlessness, a descended larynx, their thick layer of subcutaneous fat, and their early birth.  It’s a fascinating theory which turns out to be highly problematic.  Hairlessness, for instance, doesn’t correlate nicely with aquatic habitat; think of otters or polar bears (who are excellent swimmers).  Humans don’t have characteristics sea animals generally do have, such as very small ears.  Worse yet, a lot of the supposed facts of AAH supporters turn out to be just wrong– e.g. that non-aquatic mammals can’t hold their breath, that human infants are unusual in having a swimming reflex, or that our layer of subcutaneous fat is attached to the skin rather than the underlying tissue.

There’s only one chapter in the new book about the AAH, but when someone has a tendency to misquote the scientific literature, you have to mistrust what they say even on other topics.

The Descent of the Child is about babies and children.  Morgan goes over the biology of reproduction, gestation, birth, and childrearing, with a focus on where we are the same and where we differ from the other primates.  It’s a fascinating story, full of interesting facts.  For instance, we live at a much slower pace than would be expected for a mammal our size.  E.g. compared to chimpanzees, the age of puberty and our life expectancy are doubled.  Gestation proceeds at a leisurely pace, too, fitting nicely to a developmental schedule that should see the baby in the womb for 18 months.  Halfway through, the baby is evicted, resulting in an unusually inert and helpless newborn.

Her larger point is that in seeking to explain human features, scientists too often concentrate on adults only.  But the whole life-cycle is subject to evolutionary pressure, and things like the human baby’s helplessness are serious puzzles… isn’t it dangerous to have offspring that vulnerable?

At the same time, one of hte hallmarks of humans, compared with the other apes, is neoteny.  Even as adults, we are much more like ape children than we are like ape adults– in appearance, in bipedality, in general playfulness.

This touches on linguistics; Morgan suggests that it was more likely to be children than adults who originated the first language, much as the best ape language learner was the bonobo Kanzi, who picked up a keyboard-based language by watching researchings attempting to teach it to his much denser mother.

Anyway, fun book, just double-check any facts she gives before recycling them in conworlds or at cocktail parties.

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