The Third Chimpanzee

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The Third Chimpanzee: The Evolution and Future of the Human Animal’ (1991) is a wide-ranging book by Jared Diamond, professor of geography and physiology at UCLA, which applies insights from biology, anthropology, and linguistics to questions such as why one species of big mammal (humans) came to dominate its closest relatives, such as chimpanzees, and why one group of humans (eurasians) came to dominate others (Indigenous peoples of the Americas).

It also examines how asymmetry in male and female mating behavior is resolved through differing social structures across cultures, and how first contact between unequal civilizations almost always results in genocide. The book ends by noting that technological progress may cause environmental degradation on a scale leading to extinction. Diamond expanded on these themes in subsequent books: ‘Guns, Germs and Steel’ (1997), ‘Why Is Sex Fun? (1997), and ‘Collapse’ (2005).

The title of the book refers to how similar taxonomically chimps and humans are; and that their genes differ by just 1.6%, whereas chimp and gorillas differ by 2.3%. Thus the chimp’s closest relatives are not the other apes with which it is classed, but the human. In fact, the chimpanzee-human difference is smaller than some within-species distances: e.g. even closely related birds such as the red-eyed and white-eyed vireos differ by 2.9%. Going by genetic differences, humans should be treated as a third species of chimpanzee (after the common chimpanzee and the bonobo).

Part two of the book considers sexual dimorphism in mammals, and particularly humans, and the mechanics of sexual selection. It considers how across species, females are more careful in selecting their mates than males (they invest far more energy into each offspring). This determines much of human behavior, from how we pick our mates, how we organize society, and child nurturing systems, leading to differing social structures in cultures such as Papua New Guinea, Kerala, and the Christian West. It also considers questions of longevity – the previous generation dies because its biological clock shuts down metabolism and repair, so that the new progeny does not have to compete with them.

Part three extends the effects of sexual selection into language, art, hunting and agriculture, through the idea of ‘honest signaling’ – sexual signals that also cost the signer. This is extrapolated to explain the appeal of drugs. Finally, the possibility of contact with extraterrestrial intelligence (Diamond thinks that would be a disaster).

Part four considers conquest. Why is it that the Eurasians came to dominate other cultures? Diamond’s answer is that in part, this was due to the East-West layout of the Eurasian continent, due to which animals like horses could migrate from one region to another. On the other hand, migration along the N-S axis was much more difficult owing to the severe imbalances of climate. Also, the greater mobility of populations also permits greater resistance to disease, which is another reason why contact among geographically separated cultures often leads to extinction.

The process of first contact between differing civilizations is examined through the descriptions of Papua New Guinea highlanders, who were first visited half a century back. Historically, Diamond argues that such contacts between widely differing populations have very frequently culminated in the extinction of the disadvantaged groups like many native American tribes, the Tasmanians, etc.

The last section of the book argues that civilizations sometimes get caught up in internal superiority contests, and deplete the environment to such an extent that they may never recover. Examples include Easter Island and the ruins of Petra, both of which were the result of deforestation resulting in desertification.


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