Dog and man: a 30,000 year friendship

By Razib Khan | May 21, 2013 8:16 pm

Cite: Wang, Guo-dong, et al. “The genomics of selection in dogs and the parallel evolution between dogs and humans.” Nature Communications 4 (2013): 1860.

To the left is a figure which illustrates the phylogenetic inferences from a new paper in Nature Communications, The genomics of selection in dogs and the parallel evolution between dogs and humans (see Carl Zimmer’s coverage in The New York Times). Why is this paper important? The first thing that jumped out at me is that because they’re using whole genomes (~10X coverage) of a selection of dogs and wolves the results aren’t as subject to the bias of using “chips” of polymorphisms discovered in dogs on wolves (see: Genome-wide SNP and haplotype analyses reveal a rich history underlying dog domestication). The second aspect is that the coalescence of the dog vs. wolf lineage is pushed further back in time than earlier genetic work, by a factor of three. A standard model for the origin of dogs is that they arose in the Middle East ~10,000-15,000 years ago , possibly as part of the broad shift of lifestyles which culminated in the Neolithic Revolution.

This model is now in serious question. Though there have always been claims of fossils of older domestic canids (adduced as such in terms of morphology) than the ones discovered in the Middle East ~15,000 years ago, this year there has been publication of ancient mtDNA results from ~30,000 years before the present which imply the separation of putative domestic and wolf lineages at least to that date. Over the past few years I have wondered about the specific nature of the emergence of both modern humans and modern dogs, and their co-evolutionary trajectory, over the Pleistocene and into the Holocene, in light of these results.


So the preponderance of data (genomic and archaeological) leans me toward accepting the general shape and >15,000 year B.P. date for the divergence of dog and wolf lineages outlined by the authors. But there is a lot more in terms of the phylogenetics of the paper which I am not willing to agree with as so obvious and clear. In particular, the authors support a Chinese/Southeast Asian origin for the dog, rather than a Middle Eastern one. This position is backed up by the reality that the Southeast Asian dog lineages do seem quite genetically diverse, and basal to other dogs (i.e., they diverge first within the clade of domestic dogs). Additionally, in the paper itself they note that the PCA, which visualizes genetic distance, suggests that the East Asian lineages are somewhat shifted toward the wolf. Model based clustering also implies that East Asian lineages are “more wolf.”

The reason I don’t buy this conjecture is as they say in the paper itself modern distributions and relationships don’t always map onto ancient distributions and relationships. We’ve already gotten into trouble doing this for human populations of similar time depth as the new putative period of dog domestication. Ancient DNA has uncovered a great deal of discordance between the past and present. I don’t expect dogs to be any different. The authors have whole genomes of a dozen animals. When the data set is expanded to hundreds with reasonable geographic coverage let’s talk. They attempt to model some gene flow, but I suspect that this is a major problem when talking about regions of origin of a group of organisms whose divergence from the ancestral outgroup is not quite clear in its nature.

Human directed breeding. Credit: Galabwebdesign.

But, a bigger point which has less to do with the zone of origination of the dog is the mode of the origination “event.” In the paper the authors present a stark model of the classic origination event for dogs, where Ice Age hunter-gatherers adopt some puppies, and this population exhibits a sharp and punctuated divergence from the main line of the wolves.  These genetic data don’t indicate that at all. Rather, the “bottleneck” as very mild, if you could call it a bottleneck (see: Vulcans through the eye of the bottleneck). Certainly some inbred modern lineages have gone through bottlenecks, but this was long subsequent to the initial separation of dog and wolf. Rather, the authors put forward an alternative hypothesis where dogs were co-existent with early man, with a subset of wolves who were happy to scavenge on the margins of human settlements. There are variations and flavors of this sort of argument, but you can bracket them as the “self domestication” model. The reality here is that I think our explicit differentiation between forms of selection is wrongheaded, the primary issue isn’t whether dogs were self-domesticated or human-domesticated, but the rate of adaptation and demographic history. It may be that the best way to think about the origin of dogs and humans isn’t that the latter domesticated the former, but that both dogs and humans changed together as their lifestyles and interactions changed. With the rise of agriculture and increased specialization of human lifestyles there occurred a concomitant diversification of dogs.

And that is where I think the second part of the paper, focusing on parallel adaptations on the genomic level, is really interesting.

If you don’t want to click the image above, it seems that genes involved in neurological function, metabolism, and cancer are enriched in terms of signals of selection in domestic dogs. This is not surprising. Dogs exhibit great life history differences from wolves (they breed more, and are not pair bonded), and famously may be able to read human faces despite being less intelligent than wolves. And of course dogs have to eat what we eat, at least to some extent.

To understand this functional aspect of the evolutionary history of dogs though one does have to nail the phylogenetics down. So there will no doubt be more coming down the pipeline in this domain, and within the next few years the natural history of man’s best friend will be of deep interest. As ancient DNA has revolutionized the understanding of the human past, I suspect there will be attempts to analyze samples from dogs as well (though I assume that the data sets will always be thinner because scholars have always been preoccupied with human remains).

Citation: Wang, Guo-dong, et al. “The genomics of selection in dogs and the parallel evolution between dogs and humans.” Nature Communications 4 (2013): 1860.

CATEGORIZED UNDER: Evolution, Evolutionary Genetics
  • http://twitter.com/PrickEared Prick Eared

    Didn’t Bokyo already demonstrated African and Middle Eastern village dogs are just as genetically diverse as the Southeast Asian village dogs? For some reason, those who hold on strongly to the Southeast Asian origin theory tries to debunk the African village-dog discovery by citing the major trade routes in Africa and Middle East. True, their point may be valid, but no one ever seem to question the dog-consumption culture in East Asia: dogs are raised like livestock en mass which would preserve the genetic diversity. At least comparatively to the pedigreed dogs of Europe.

    • razibkhan

      dogs are raised like livestock en mass which would preserve the genetic diversity.

      not convincing. livestock can be subject to powerful selection and reduce genetic diversity.

  • marcel proust

    The second aspect is that the coalescence of the dog vs. wolf lineage is pushed further back in time than earlier genetic work, by a factor of three.

    Um… 3 possibilities: (1) that word does not mean what you think it means (least likely), (2) I do not understand what is going on here (more likely), or (3) you meant to type divergence.

    Please elucidate (or correct if that is called for).

    • razibkhan

      i should have used divergence. but i was talking about this:

      http://en.wikipedia.org/wiki/Coalescence_(genetics)

      • marcel proust

        Thank you. This is why I nitpick. Often, what appears even to me to be nitpicking is actually reflective of my ignorance: so I learn something when my nitpicking is corrected.

  • Dmitry Pruss

    Moderate bottlenecks would skew allele frequencies and make PCs somewhat less useful? And the greater diversity / more root-like quality of the Asian breeds may be a mere result of the past admixture from wild canine subspecies, some possibly extinct?

    • razibkhan

      1) i think the past admixture is a big issue i want them to tackle more thoroughly

      2) the bottleneck is so attenuated. not sure it would skew the pca that much (16% at N1 vs. N0).

  • http://twitter.com/TKosmatka Ted Kosmatka

    Here’s a nice map of dog/wolf mitochondrial haplotypes, with a focus on dingos. Interesting to note that haplogroup d is found in putative ancient European dogs like the elkhound and the lapphund, which does seem to place them somewhat apart, and suggests either a unique domestication event or more recent cross-breeding with wolves. http://php.med.unsw.edu.au/embryology/index.php?title=File:Dog_mitochondrial_DNA_variations.jpg

  • http://www.facebook.com/peter.h.bradley Peter H. Bradley

    I am thrilled that this progress researching the history of dogs has been made. I have intuitively “known” the truth for some time now, though it is based on my background as an athropologist, so I’m going say what we will all soon learn. The human-dog link-up actually starts back about 50,000 years ago (or more) and is part and parcel to the last great expansion of modern humans out of and away from Africa. The “wolf” involved probably looked a lot more like an Ethiopian Wolf or a Dingo than a Timber Wolf, thus explaining some of the differences in basal behaviors. I suspect all the different wild and domestic “yellow dogs” of today are closer to the final dog-human “product” than a modern wolf. Dogs evolved to feed off of Rodentia, thus the elongated “capture and hold” jaw and dentition composition and the from-birth “instinctive” ability to shake their head violently, rendering death in a small victim in a millisecond; not the sloppy, slow and unnatural pack slaughter seen in modern wolves and some wild dogs. The “where” of the human-dog link-up is much less important to me, because it clearly is something that took a little time and humans were moving pretty fast back then. So I suppose it may have actually started in Africa and developed through the middle east, the caucasus, India, and southeast Asia. This, to me, makes sense. I also feel we will learn more about the shared biomes, that is, the shared microscopic flora and fauna that have influenced the development of both animals, us and them. There is at least one study that indicates that babies raised in a house with a dog, on average, are healthier babies. Dogs were absolutely invaluable to early humans for several key reasons, which is important because they have always been “expensive” to maintain in terms of caloric consumption, which otherwise might be feeding the humans. But in acient times, they largely fed themselves, ridding the immediate area of rodents, which retained its value after humans started farming. That is reason #1. Reason #2 is that they were our first “early warning system”. Their senses, so much better than ours, could detect the pending presence of other humans and sound the alarm. Since these “other humans” probably meant to kill us, that was a very, very good thing. Reason #3 is that, quite simply, dogs were our emergency fall-back food source. They were our first domesticated farm animal, so to speak. The plains indians had a expression for when times that were really, really bad: they would refer to them as “when we eat our dogs”. This explains much of our own behavior to this day: there is no other animal on earth that we will adore so much in one moment and treat with such horrific coldness the next. Our best friend, indeed.

    • Janice Burns Chainey

      Enjoyed your discourse. Now I know why I call myself “doglady”.Didn’t get my first dog until I finally lived in a house and wrote a letter to Pets and Pals of Oakland, CA ,(years ago)My mother put me up to writing the letter. I always felt I won because it may have been the only letter. But small world connection. One of the judges, unknowingly, was married to a distant cousin of mine. I have had several dogs, all best friends. Can hardly take care of myself these days, or I’d get a “labradoodle.” Cats are o.k., but my heart belongs to the pooch.Today I am very supportive of specialty working dogs.One can have no better friend than her dog.

NEW ON DISCOVER
OPEN
CITIZEN SCIENCE
ADVERTISEMENT

Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!

Gene Expression

This blog is about evolution, genetics, genomics and their interstices. Please beware that comments are aggressively moderated. Uncivil or churlish comments will likely get you banned immediately, so make any contribution count!

About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at http://www.razib.com

ADVERTISEMENT

See More

ADVERTISEMENT

RSS Razib’s Pinboard

Edifying books

Collapse bottom bar
+

Login to your Account

X
E-mail address:
Password:
Remember me
Forgot your password?
No problem. Click here to have it e-mailed to you.

Not Registered Yet?

Register now for FREE. Registration only takes a few minutes to complete. Register now »