A number of years ago, I found a family of raccoons living in my chimney.1 I got them out by dropping a trouble light down the flue and turning it on for a few days. According to Richard C. Francis, in his splendid book, Domesticated, animals such as raccoons living in urbanized areas represent the first step toward domesticating those animals.
The full title of the book is Domesticated: Evolution in a Man-Made World, and Francis shows in considerable detail how various animals became domesticated: dogs, cats, pigs, sheep and goats, reindeer, camels, horses, rodents, and perhaps humans, as well as other predators such as raccoons and ferrets. Each scenario is slightly different, each seems well documented, and each has just a little bit of just-so story in it.
The audience for the book is not completely clear. I think the author thinks that the book is written for the lay reader, but at times it got a little hairy, and I recommend that, if you are not a biologist, you keep your computer nearby. Or, if you are younger than I, your smart phone. Indeed, after getting through 50 or so pages of the complimentary copy I received, I bought a Kindle edition, precisely so that I could more easily look up terms that were unfamiliar or not entirely familiar. Lest this paragraph be taken as a criticism, let me make clear that the effort was wholly worthwhile.
Francis begins with the now well known domestication of foxes by Dmitry Belyaev in Siberia. Belyaev and his colleagues selected foxes, as Francis puts it, “for one trait and one trait only: the capacity to tolerate human proximity without fear or aggression.” In approximately 50 years, they bred foxes that were as tame as many dogs. But there were concomitant physical changes: hair became mottled or piebald, ears flopped, tails curled, snout and limbs shortened, and face broadened, for example. Additionally, brain volume and sexual dimorphism were reduced. Many of the same physical changes may be seen in domesticated dogs, cats, horses, cattle – and all are a direct result of selection for tameness. Such by-products are a general feature of evolution and are a form of convergent evolution resulting from various homologies that more or less guarantee that all domesticated mammals will evolve similar traits.
The raccoons in my chimney are probably already self-selected for tolerance of human beings. Wolves probably self-selected in roughly the same way: perhaps they began to domesticate themselves by feeding on scraps left by early humans, as the raccoons occasionally feed on my garbage. Wolves in different geographical areas evolved into landraces, sort of proto-breeds that eventually developed into what we know as breeds.
I was surprised to learn that the concept of breed is only a century or so old. British kennel clubs, beginning in the 1870’s, hyper-selected for various traits, such as the snout of a bulldog. Francis says that they routinely mated a champion male with his own female offspring and remarks somewhat archly that the Victorian aristocrats ultimately responsible for such incestuous relationships may have been desensitized as a result of their own pedigrees.
Besides causing inbreeding, such selection also caused serious physical and genetic defects in virtually all purebred dogs. Not to mention that thoroughbred horses, which Francis deals with in a later chapter, are at an evolutionary dead end: they are infertile, and their speed has not improved in 50 years. There are no master races; they need to be mongrelized.
Cats also enjoyed a commensal relationship with humans, probably after the mouse was introduced into the wild cats’ region. Although humans consider cats somewhat standoffish, Francis notes that feral housecats remain far more tame and far more gregarious than their wild ancestors. Like dogs, cats have been bred to have various skeletal deformities, a practice that Francis considers “unconscionable.”
Pigs may have been domesticated similarly to dogs, but it is also possible that pigs, cattle, sheep, goats, and horses were domesticated by “human management of wild populations,” wherein wild animals were first herded, then bred. Cows, in particular, descend from the wild aurochs, a large, fierce beast that Caesar compared, with some hyperbole, to elephants. Regarding the aurochs’s ferocity, Francis writes,
[N]o matter how tame these early domesticates were, by auroch[s] standards, you would still need to be a lot braver than a bull leaper to push their calves aside and pull on their teats.
(What’s not to like about a book that regularly comes up with quips like these?) Francis seems to have forgotten, however, that elephants have been domesticated, and he writes that the aurochs is the largest domesticated animal. Oddly, he thinks (incorrectly) that the singular of aurochs is auroch. In fact, the singular is aurochs; the word is cognate with ox (think ur-ox). It is odd that the copy editor did not catch this mistake, because the book seems to be generally well prepared (we will not, however, discuss the use of grizzly where grisly was meant).
Sheep and goats (Francis prefers goats), reindeer, camels, horses, rodents: Francis covers them all, often beginning a chapter with a curious anecdote. Horses, for example, were originally domesticated for their meat; only later, after other meat sources were available, was the horse used for transportation and warfare. The horse’s status has risen so sharply that most Europeans and their cultural descendants “would be about as aghast at the thought of eating horse meat as they would dog meat.”
Francis devotes 2 chapters to the question whether humans domesticated themselves. The argument is long, and I am afraid you will have to read it for yourself, but it depends in part on the argument that humans, like other domesticated animals, are neotenous, that is, the adult animal retains juvenile features, such as big eyes. I got slightly bogged down in one chapter by the profusion of terms like hominid, hominin, hominine, and hominoid (which I think of as homonym-oids). The second of these chapters asks whether human hypersociality came as the result of self-domestication by way of natural selection for tameness. Answer: “It ain’t necessarily so”; Francis wants more evidence.
The final chapter, except for an epilogue, is called “The Anthropocene” and asks how an utterly obscure, bipedal, nearly hairless ape could in a mere few hundred thousand years come to dominate the planet and indeed be responsible for the most recent mass extinction. I cannot go into detail here, but I am left with the feeling that it was mostly “cultural evolution,” with biological evolution following thereafter – as when herdsmen begin to use dairy products (cultural evolution) and only thereafter does an allele for lactose tolerance predominate (biological evolution).
Appendix 1. I resolved not to read the appendixes; generally I do not like appendixes or endnotes1 and think that a topic should be incorporated into the book if it is important enough and dropped if it is not (excluding very abstruse derivations and whatnot). Nevertheless, I began to read the appendixes and was treated to a discussion of the need for a new synthesis that gets away from the gene-centered view popularized by Richard Dawkins, a serious and hard-hitting critique of evolutionary psychology, and also some boring stuff.
Appendix 2. As one of the self-appointed guardians of the modern metric system, I disliked the book’s use of “mya” for “million years ago”; if anything, the usage should have been “Mya.” But that is not really satisfactory either, because “y” and “a,” though not SI symbols, are both commonly used as a symbol for “year.” I probably would have used “Ma” for “megannus,” since “year” is Anglocentric.
In addition, when he means tens or hundreds of thousands of years, the author uses “BP,” presumably meaning “before present,” which is arguably OK, but not consistent with the previous usage. At least once, he used “CE,” which is perhaps more useful than “BP” when we are discussing more or less historical times, but again is inconsistent.
1 My son also had a raccoon in his chimney; unfortunately, his died there, with unfortunate consequences involving maggots. I really did not want to tell you that, but I wanted to make a point about the endnotes. The book has a significant number of endnotes. Many of them simply cite a reference, but others have content. I find it very distracting to have to stop my reading and go to an endnote. Part of the art of writing is culling: if something was worth telling, the author should have worked it into the text or, otherwise, killed it.