Saturday, October 18, 2014

Domestication and human evolution, streaming!

Domesticated humans, domesticated canids, domesticated finches! The Center for Academic Training & Research in Anthropogeny held a conference on domestication and human evolution, and live streamed it. I watched live, refusing to speak to my husband or dogs during it, which didn’t go over well. You, however, can watch the archive on YouTube.

The conference was a series of short talks from researchers. These included:

Robert Wayne, “The transformation of wolf to dog: history, traits, and genetics”

Wayne’s lab published a recent genetics paper on exactly where the dog was domesticated, and in this talk he stepped us through their findings. Previous work (and there has been plenty of it) on the location of dog domestication has begun with the assumption that dogs evolved from a population of wolves which still exists basically unchanged, inhabiting the same range now as it did then. Previous work has suggested that this occurred in Asia or the Middle East. Wayne’s group argues that the population of wolves which gave rise to dogs no longer exists, but lived in Europe about 20,000 years ago. It’s a different perspective on a question which is very difficult to answer, because dogs continue to interbreed with wolves so freely that these genetic studies are awfully hard to interpret.

Anna Kukekova, “Fox domestication and the genetics of complex behaviors”
This talk came out of the lab where I work and I got to see my own name on the list of contributors at the end of the talk. Kukekova gave an overview of the history of the fox domestication project, in which lines of foxes were selectively bred for tame temperament or aggressive temperament, and recent research. Our lab digs in to the question of what it is in the genetics of the tame foxes that makes their personalities so different from those of conventional farm foxes. Since this conference was about domestication, and the tame foxes are the best known and longest running domestication study, speakers returned to the foxes throughout their talks. They are a tough nut to crack. Behavior is exceedingly complex mechanistically and we (by which I mean all behavioral geneticists, not just our lab) are still trying to figure out how to get a handle on the genetics that affect it.

Robert Franciscus, “Craniofacial feminization in canine and human evolution”
Craniofacial feminization means that your face is flat, basically. Look at the reconstruction of a Neanderthal face: the chin juts out. Look at a modern human face: flat. Look at a chimpanzee face: jutting chin. Look at a baby chimpanzee: flat. Do humans look like baby chimps? We kind of do. Is there a significance to this? Franciscus argued convincingly that there is, and discussed differences in dog versus wolf muzzle length (and got quite technical about how his group investigated them). We don’t know why this feminization or neotenization (childlike changes) happens in domestication, but it seems to be a recurrent theme. This was the first talk that really grappled with the idea that humans are domesticated, with changes compared to our recent ancestors that parallel changes between dogs and wolves, or between tame and conventional foxes.

Terrence W. Deacon, “The domesticated brain”
Do domesticated animals have smaller brains than their wild counterparts? This is certainly the case in dogs and wolves. Is it the case in humans and our ancestors? Deacon’s group has studied Neanderthal brain size based on their skulls, and they conclude that modern humans do not have clearly smaller brains. He noted that the tame foxes also do not appear to have smaller brains than their conventional counterparts. Why does the difference in brain size show up in only some, but not all, examples of domestication? Is it perhaps not a necessary part of the domestication process?

Phillipp Kaltovich, “Neotenous gene expression in the developing human brain”
It is pretty difficult to study gene expression in human brains, because you have to cut up brains to get your data. Kaltovich did get his data from somewhere, though, and it was really interesting to see his comparisons of gene expression in young versus older brains. The question was whether gene expression changes with age, which helps get at the bigger question, are there gene expression differences in domesticated species compared to their wild counterparts, and are these expression differences similar to the differences in young versus mature animals? In other words, are domesticated species basically enternally young (neotenized)? He did find differences, but his group will have a long way to go to put them together into findings that really illuminate the domestication question. I have a lot of sympathy for how hard this particular approach is, as my research is currently also focused on brain gene expression.

Tecumseh Fitch, “The domestication syndrome and neural crest cells: a unifying hypothesis”
In a recent paper, Fitch’s group put forth the concept of a domestication syndrome, a set of changes associated with domestication: flatter face, behavioral changes, white markings, etc. Subsets of these changes are seen in all domesticated species. Fitch’s group hypothesizes that a particular kind of cell involved in early development is involved in all of these changes. This cell, the neural crest cell, migrates through the growing embryo and develops into many different structures and cell types, including coloration cells (explaining white markings), teeth (explaining dentition changes), and the adrenal medulla (source of adrenaline, explaining behavioral changes). It’s an interesting hypothesis and I’ll be curious to see where this group goes with validating it.

Kazuo Okanoya, “Domestication and vocal behavior in finches”
Okanoya’s group studies a species of domesticated finch and its very closely related wild ancestor. The wild finch has a simple song, while the domesticated species has a quite complicated one. Okanoya’s group investigates the difference in these songs, as a model for the development of complex language in domesticated humans. He played both songs, wild and domesticated, and the difference was dramatic. He linked the changes in the song between species to sexual selection.

Richard Wrangham, “Did Homo sapiens self domesticate?”
The question of self domestication was one of the recurring themes of the conference, and for me this was the most transfixing session. Wrangham studies chimpanzees and bonobos, two closely related species with very different aggression levels, as models of the difference between humans and our more aggressive, non-domesticated ancestors. He defines domestication as the reduction of reactive aggression. Reactive aggression is different from proactive aggression: humans are quite good at controlling our reactive aggression, as we are able to tolerate strangers and live in large groups very well. But we do still show significant proactive aggression, which he described as aggression performed in cold blood, such as armed robbery. Wrangham suggests that a reduction in aggression is the trait evolutionarily selected for in self-domestication, and the other parts of the package (flatter faces, white markings) come along for the ride as associated traits. Self-domestication is often seen in island species, and he gave the example of the red colobus with a neotonous (childlike) island version compared to the mainland population.

The whole conference was really fascinating. It’s available on YouTube now, so go, check it out!

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