Animal domestication

Published on July 1, 2014   47 min

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Other Talks in the Series: Agricultural Genetics

This talk is on animal domestication. I'm Carlos Driscoll, Chair in Conservation Genetics at the Wildlife Institute of India.
In this talk, we'll cover the basic questions regarding where, when, and who achieved domestication and touch on why those people might have made the transition from hunting and gathering to agriculture. And then we'll move into the deceptively simple question of what domestication actually is and how, in an evolutionary genetic sense, it came about. That should allow us to transition to thinking about domestication in terms of molecular genetics. And finally, to briefly introduce the field of behavioral ethics. But before all that, we'll introduce the topic with a few slides on what domestication has done for us as humans. Throughout the talk, animal domestication is considered in the light of evolution, and that seems a good place to begin.
Darwin first described natural selection in 1859, with "On the Origin of Species." Sexual selection was introduced in "Descent of Man, and Selection Related to Sex" in 1871. In between those two, in 1868, he published the "Variation of Animals and Plants Under Domestication." In this work, he looks more deeply into artificial selection. Domestication, the most obvious exemplification of artificial selection, was something that very much interested Darwin. He felt that an appreciation of animal domestication was important not only in its own right, but as a key to understanding natural selection, and hence evolution in general. Here he was using domestic animal breeding as a faster-paced analogy for evolution by the gradual and accumulative force of natural selection. Because Darwin saw that one could experiment with domestic animals, breeding various strains together or selecting for certain traits, things that could not be done with wild animals in anything close to the same way. But on any farm, one could study the properties of varieties and dynamics of adaptation firsthand. So here he uses the tangible and familiar results of artificial selection by farmers in his argument that selection by natural means, survival of the fittest, was not just plausible or possible, but probable. If humans could do it in only a few hundred years, then nature must surely be able to do the same thing over millions.
Yet artificial selection is distinct from natural selection in that, as the name suggests, it's somewhat unnatural, being driven by human activity and intention rather than the stochastic and mechanistic workings of the physical universe alone. By manipulating the accumulated genetic variation found in plants and animals, by domesticating them, man was able to harness the patrimony of almost 4 billion years of life on Earth. And the results have clearly been profound and have been fundamental to our success as a species. Beginning between 12,000 and 10,000 years ago, with the advent of plant and animal domestication, we began the transformation of most every natural ecosystem on Earth. This has continued to the present day when now, the knock-on effects of these changes even challenge the basic health of the planet.
The revolution that domestication powered, the Neolithic Revolution, changed everything. Consider that today, 12% of the world's surface is taken for agriculture. 70% of the fresh water consumed is used to water it.
The conversion of natural ecosystems to agriculture is the primary driver of habitat loss. And habitat loss is a primary driver of animal extinction.
Consider then that naturally evolved species are now going extinct at a rate 100 to 1,000 times faster than the background extinction rate. Yet no domestic animal has ever gone extinct.
The results of artificial selection are undeniable. The advantages of agriculture make it seem as if humans have escaped the struggle for existence, that concept Darwin took from Thomas Malthus and used to formulate the theory of natural selection.
This food production allow the population to grow from around 10 million in the Neolithic to more than 7 billion today, and still growing. But more than simply us growing our own food, the Ag Revolution was the spark for an entire economy, one that includes trade in plant and animal products, the development of towns and then cities, and really the beginning of culture as we know it today. So as a species, we owe almost everything modern to the fact that artificial selection can work to modify the natural result of evolution to human ends. If we stand back and look at human history in the light of evolution, we see that manipulating the genetic architecture of plants and animals has been our most transformative and certainly our most important achievement.