Dogs are not Domesticated Wolves

At some point long ago, our ancestors domesticated dogs and we've been constant companions ever since. In a study recently published in PLoS Genetics, an international team of scientists used high-throughput sequencing to try to unravel the when and where of that important event, but came away with surprising answers and new questions.

To investigate where our familiar dogs have come from, the team sequenced the genomes of three gray wolves (Canis lupus) from Croatia, Israel, and China (chosen to represent the three regions where domestication may have happened), two dog breeds (a Basenji and a Dingo, both breeds from areas that have been isolated from modern wolves), and a golden jackal (Canis aureus). They compared the genomes with one another and with the previously sequenced genome of another dog breed, a Boxer (from Europe).

Based on their analysis, the team concluded that dogs and wolves parted evolutionary paths sometime between 9,000 and 34,000 years ago. That predates our development of agriculture, supporting the idea that dogs accompanied our hunter-gatherer forebears and only later adapted to an agricultural lifestyle. Of more interest, though, is the fact that the three dog genomes formed a sister group to the wolves, rather than clustering under one of them. That finding suggests that dogs share a common ancestor with wolves, rather than having been domesticated from them. "Dog domestication is more complex than we originally thought," said John Novembre, a senior author on the study, in a press release. "In this analysis we didn't see clear evidence in favor of a multi-regional model, or a single origin from one of the living wolves that we sampled. It makes the field of dog domestication very intriguing going forward."



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There are several possible explanations, but the team's favourite is that the common ancestor of dogs and wolves has gone extinct since they diverged. Both groups experienced population bottlenecks shortly after they diverged, so their common ancestor was probably within the lost diversity. "One possibility is there may have been other wolf lineages that these dogs diverged from that then went extinct," said Novembre. "So now when you ask which wolves are dogs most closely related to, it's none of these three because these are wolves that diverged in the recent past. It's something more ancient that isn't well represented by today's wolves."

I struggled for some time with the first sentence of this post, and the research findings justify my misgivings to some extent. It's conventional to talk about humans 'domesticating' other organisms, but I'm a bit uncomfortable with the dynamics inherent in that terminology. It casts us as the agents: we are the dominant, active player shaping the natural world to our whims; we are subjects and they are objects. Yes, humans have shaped the evolution of many other creatures, even carefully breeding to produce particular traits or combinations of traits, but the process is often reciprocal (regardless of whether it's consciously directed). For example, human populations which regularly consumed dairy experienced selection for lactase persistence. The line between domestication and coevolution is often blurry, if it exists at all, and the dynamic between early dogs and our hunter-gatherer ancestors strikes me as an excellent example. Both groups doubtless benefited, and I find it hard to describe the exchange as "domestication". Yes, we influenced their evolutionary course, but I wouldn't be surprised to discover that they've done the same to us. What about you? Can you think of any ways that dogs may have influenced our evolution?

References
Freedman AH, et al. Genome Sequencing Highlights the Dynamic Early History of Dogs. PLoS Genetics 10(1):e1004016. (2014) doi:10.1371/journal.pgen.1004016
Press release from the University of Chicago.

Image credit
The wolf image is by Gunnar Ries via Wikimedia Commons.
The population tree is Figure 5A from Freedman et al (2014).