Domesticated: Evolution in a Man-Made World

Three years ago, I made the decision to adopt a pet of my own???specifically, a cat. In my mind, a cat was the ideal companion for someone like me: independent enough that I could leave it alone while I was at work, but companionable enough to pet and play with when I was at home. I had actually managed to talk my mother around to the idea, and had begun to lay down some fairly concrete plans (including which rescue organisation I was going to adopt the cat from, as well as a budget for food, toys, vaccinations, and so on) but the plan was sunk when my father refused to have a cat in the house???not because of any health concerns, but simply because of dislike (or, as I like to think, unwarranted prejudice).

But I still wanted a pet of my own, and since I couldn???t get a cat, I decided to go for a dog. In this regard, I had to be a bit more thorough: it would have been all right to bring a kitten of unknown heritage into the household, but dogs were another thing entirely due to size and temperament concerns (more so, since we already had two other dogs in the house). In the end, I wound up adopting the offspring of my aunt???s Shih Tzu: a sensible move, since I didn???t have to pay a breeder for the privilege of adopting the puppy, plus we already had two other Shih Tzu in the house; one more would fit in perfectly.

The experience I???ve outlined above???particularly the questions about size and temperament???are questions responsible pet owners ask themselves before they adopt an animal to bring into their home. Whether a person winds up bringing home a cat or a dog (or something else entirely), long-haired or short-haired (or feathered or scaled), purebred or mixed-breed, really depends on the owner???s preferences and requirements (and in my case, the preferences and requirements of the other household residents). However, the only reason such choices can be made, and made with relative confidence, is because of the long history of domestication that both the cat and the dog have undergone. It is this process of domestication that Richard C. Francis tackles in his book Domesticated: Evolution in a Man-made World.

Domesticated is divided into fifteen chapters, plus a preface and an epilogue. Chapters 2 to 12 focus on familiar domesticated animals such as dogs, cats, and various familiar farm animals like cows and pigs. There is also a chapter devoted to reindeer, another dedicated to the camel, and one dedicated to rodents (which include not just pet rats and lab mice, but also rabbits and guinea pigs). One chapter, titled ???Other Predators???, focuses on raccoons, ferrets, and minks. The last three chapters are dedicated to us: humans. In these chapters, Francis suggests that humans might be ???self-domesticated???, a process that allowed our species to rise to its current level of dominance.

Throughout the book, Francis emphasises the role of ???tameness???. While most people understand it as a particular behavioural trait that makes animals more pliant to human presence and influence, Francis offers an alternative definition for tameness, one that is rooted in genetics. In the first chapter, he explains this by discussing Russian geneticist Dmitry Belyaev???s long-term experiment on farm foxes:

[N]oteworthy is the way the fox ???> fox-dog transition parallels the wolf ???> wolf-dog transition, especially in the correlated by-products of selection for tameness, from floppy ears to shorter snouts. At bottom, this parallel response reflects shared developmental processes in the fox and the wolf, which you might expect, given their genealogical proximity on the tree of life. But many of these correlated responses occur in other domesticated mammals as well, some quite distantly related to canines. Some are even found in domesticated birds and fishes. So consistent is this suite of changes, in fact, that it has a name: the ???domesticated phenotype???.

From here, Francis launches into an exploration of the evolutionary history of common domesticated mammals, following the concept that the domesticated phenotype existed in the wild ancestors of domesticated species, but through a combination of natural and artificial selection, those animals with the highest propensity for tameness were given preference over those with a lower propensity, and therefore became the domesticated species we know today. For instance, in ???Chapter 2: Dogs,??? Francis explains how self-taming might have been the very first step towards domesticating the wolf, an otherwise deadly predator of humans:

Wolf domestication was initiated by wolves, and it required that an evolved psychological barrier be surmounted, or at least eased, such that they tolerated closer human proximity than did their forebears.This process of self-taming was accomplished by standard natural selection. Among the wolves that hung around human encampments, those that better tolerated human proximity got more scraps and hence left more offspring than did their ???wilder??? cohorts. This naturally selected tameness was the first step towards dogness, and it may have taken thousands of years.

Self-taming also explains why there are still wild wolves: not all wolves had the necessary genetic makeup to become tame, and so remained as they were, while the tamer wolves were taken in by humans and, through artificial selection, transformed into the many breeds that exist today.

Francis clarifies, however, that the self-taming process didn???t occur in the same way for all domesticated animals, and therefore didn???t always produce animals with the same behavioural traits as dogs. Cats, for example, were domesticated through a somewhat-different route from dogs, which explains why, despite their domesticated status, they remain far more independent than canines:

The genetic evidence???indicates that Near Eastern wildcats were first domesticated in the cradle of agriculture, called the Fertile Crescent, around 10,000 BP [Before Present]. It was here that humans first began to store grains. These stored grains proved vulnerable to a recent invader from northern India, called the house mouse (Mus musculus). For the wildcats in the area, these house mice were a new reliable food source, so some wildcats began hanging around human settlements. ???In essence, human agrarian settlements provided the wildcats in the area a new niche, which required different behavioural dispositions than the old relatively human-free niche had required. Through natural selection for tameness, a subset of the wildcats was able to increasingly thrive in this new niche. But in contrast to dogs, which also exploited this niche, even the more tame wildcats retained their previously evolved hunting skills and equipment.

While self-taming is largely governed by natural selection and therefore takes a very long time, domestication and artificial selection occur in a much shorter time frame. This is due to the fact that the domesticated phenotype includes a tendency towards individuals reaching breeding age earlier in their lifespan, as well as gaining the ability to breed year-round; as a result, it is easy for humans to breed for specific traits and see results quickly (evolutionarily speaking).

Unfortunately, domestication has not necessarily been good for the animals that have undergone the process. Given the time span at which natural selection occurs, artificial selection must be sped up as much as possible in order to get results within a human???s life span. However, this can only be achieved by inbreeding, which has created some very negative effects. Dogs best exemplify those negative effects, as Francis points out when talking about the history of dog breeds and why there are so many of them:

[A]rtificial selection will rapidly get you large phenotypic changes, but at a cost. First there is the cost of inbreeding and the inevitable accumulation of deleterious mutations. Virtually all purebred dogs have a host of genetic ailments, from narcolepsy to skeletal defects. ?????? Under the auspices of the kennel club, the Cavalier King Charles spaniel recently evolved a brain that is too large for its skull???a condition known as syringomyelia. The effects are variable but often involve excruciating pain and ultimately paralysis and death. You would think dogs with this condition would not be bred, but you would be wrong. The problem is that the symptoms often do not become manifest until three or four years of age, and breeders don???t wait that long. Several recent dog show champions that died of this disease sired numerous offspring, sometimes through mating with their daughters. This is truly perverse, both evolutionarily and morally.

He later goes on to explain that the same is happening to cats, though the intensive breeding for felines has been fairly recent compared to dogs. However, despite the fact that most breeders are now currently trying to breed out pre-existing genetic disorders, as well as avoid introducing more, there are still some people who still insist that it???s all right to breed animals with debilitating physical features in the name of ???cuteness???:

There is another mutation, called radial hypoplasia (RH), or ???hamburger feet,??? which results in a different form of polydactyly, of a spiralling nature. A creative breeder in Texas sought to build on this deformity by constructing a ???Twisty cat??? breed, in which the spiralling extends to the bones of the forelimb. Twisty cats also have extremely short forelimbs and relatively long hind libs, which cause them to sit up like a squirrel???hence an alternative name, ???squitten.??? Twisty cats are banned in Europe on humanitarian grounds, but not in the United States; the same is true of the Munchkin. ??? The deliberate breeding of skeletally deformed breeds is unconscionable.

Again, in the subsequent chapters, Francis makes clear that, though the intensity of artificial selection under the auspices of domestication varies from species to species, it hasn???t always been good for the animals subjected to it. The same might be said of their wild ancestors: after all, the auroch (the ancestor of all domesticated cow breeds) is extinct, and so is the wild dromedary camel. While domestication has proven useful for the survival of those few fortunate species that have been selected for it, it has also proven detrimental, both to the animals themselves, and their wild ancestors.

Now, while I don???t expect any non-fiction book to be easy (after all, I read these books partly to learn new things, and learning new things isn???t going to be easy), I do expect the language to be approachable by the average reader. Francis??? language is not that: he tries, but there is a lot of jargon in his text that only a biologist would understand, and even when he tries to explain the jargon, his language can still be confusing???an inability to use ???small words???, as it were. While it won???t stop the determined reader from finishing the book (as I did), it does make for very, very slow reading. I found myself having to reread passages from time to time, sometimes entire sections. I would also have to go online every so often to look up what certain terms meant. While doing those things is no great hardship, it did slow me down significantly.

However, despite that issue, Domesticated is well-organised and thought out. Francis takes time to provide all the information at his disposal (the Notes and References section is substantial, to say the least), and organises it in a logical manner. This neatness of organisation and logic makes the book tolerable to read despite the difficulties the reader may have with the language. Francis also includes some personal anecdotes (the most charming include one about his cats, and another about the first time he rode on a camel), but he doesn???t focus on them overmuch; instead, he uses them as lead-ins to other, more important ideas and histories???which is precisely how any non-fiction writer worth their salt ought to use personal anecdotes in the first place, if they are not writing a memoir.

Overall, Domesticated: Evolution in a Man-made World is a fascinating and insightful read. Francis takes the time to lay out his premise, and build upon it in a logical fashion, so that by the time he makes the main point of his argument, the reader understands how he arrived at that conclusion. He is also very careful to present both sides of an argument (particularly in the last three chapters, which focus on human evolution), and although he makes it clear which side of an argument he prefers, he takes the time to outline why he thinks the way he does, and to present the other side???s points fairly and clearly.

However, despite Francis??? clear (and deeply appreciated) academic integrity and scientific insight, he doesn???t quite have the ability to write in an accessible way. His writing is riddled with jargon, and though he does try to explain that jargon in the simplest possible words, his idea of ???simple??? probably only applies to people with Biology degrees. While it is possible for the layperson to make it through the book with a lot of help from the Internet or a friend with the necessary knowledge, it???s still a very slow read. This may or may not put potential readers off, but I think that if one is interested???and stubborn???enough, this is a book might prove to be remarkably enjoyable.