This is a quick thought, prompted by reading about the purported “self-domestication” of bonobos (article link). The idea is that bonobos are the highly-sexed, peace-loving apes that they are because, unlike chimpanzees, they didn’t have to compete with gorillas for food. They lived south of the Congo River, in an area isolated by drought, where gorillas couldn’t survive. Freed of the brutish struggle for existence, they dropped many of the competitive behaviors that chimps display, and became more matriarchal, more prone to negotiate than lash out. In other words, they started acting more like domestic animals. They self-domesticated.
Or so the hypothesis holds. I suspect there are a number of problems with this, starting with reports that wild bonobos don’t act quite the same as captive ones, but whatever. Let’s assume for a moment that this idea is right, that some species “self-domesticate” by becoming more social and cooperative. Let’s also assume that modern humans are one of the self-domesticating species. Perhaps we’re the bonobos to Neanderthal chimps? Except for the inconvenient fact that there were at least two if not four other species of hominids around at that time, the analogy is seductive.
What caught my attention was an idea from Judith Stamps, a professor emeritus at UC Davis, that self-domestication might be favored on islands. That got me thinking, because I’ve had a bit of experience on islands.
Islands have some classic problems: island animals don’t fear humans or introduced predators. Insular plants lack the defensive compounds of their mainland relatives. When mainland animals and plants get to islands, chaos typically ensues, and as a result, island species are disproportionally represented on endangered species lists. The classic explanation is that in the absence of predation, island organisms evolve to stop wasting their resources on defense, and instead pour those resources into living. Or, as I put it, instead of living in the South Central mainland, with the bars on the windows and the guns by the bed, the island species live on the insular West Side, where they compete through finances, conspicuous consumption, and social displays, and investing in financial instruments instead of home defenses.
Now look at these characteristics again. Island animals are tame. Island plants are highly edible, often with bigger leaves and blander fruits. Does this remind you of anything? It should. It sounds like a farm or a garden.
Perhaps domestication is more about turning farms and gardens into islands, and this habitat, as much as selective breeding, selects for the species that can survive on those islands. Yes, of course humans are the primary environmental filter, and species that don’t play well with humans get voted off our islands every time we weed. Yes, we routinely breed and select for organisms with the traits we like. Still, maybe domestication is less about selective breeding, and more about habitat manipulation. When we made habitats for humans through gardening, we created a myriad of islands for evolution to work on.
Perhaps Insularizaion causes self-domestication. Bonobos may have self-domesticated in a forest island on the south side of the Congo River. Modern humans may have self-domesticated on the coast of southwest Africa some 80,000 years ago, when the population geneticists say that our species almost went extinct. Being stuck on a small island of favorable habitat might have helped us evolve more sophisticated social cognition, something that later served us well, when more favorable climates let us spread across the world. Perhaps all episodes of domestication (or self-domestication) happened this way. It’s a testable hypothesis, more or less.
Now, our islands of agriculture have spread across the world, becoming a major biome in their own right, and our defenseless crop species, as tame as any island species, are everywhere. One irony of this situation is that wildlands are more and more becoming islands. We may see self-domestication in some of the remaining wildlife, if our society doesn’t collapse first. This is a big concern among land managers, who are now attempting to maintain connections among reserves, but many urban parks are already isolated. Will park plants and animals lose their defenses? We’ll see.
The other irony is that the sheer expanse of domesticated landscapes now favors the evolution of species that can take advantage of these resources, species we call weeds, pests, and pathogens. Things that don’t need to play well with others in a limited space, because space is no longer so limited. These evolving super-pests are de-domesticating themselves, abetted by our efforts to control them.
We may be in for interesting times ahead, with rewilding farms and self-domesticating parklands. Nice to know that the future will be interesting, in the proverbial sense.