Ever wondered how the ancestors of your beloved goldendoodle became “man’s best friend?”
-Sena McCrory |
| Photo by Robert Clark |
The domestication of dogs is perhaps one of the greatest examples of co-evolution in human history, and one that has stumped scientists and anthropologist alike for years.
An international team of researchers led by Swedish biochemist Erik Axelsson recently published an article in Nature that describes how genetic changes in wolves could explain the beginning of the relationship between man and canine. The secret lies in a dog’s superior ability to digest starches.
DNA from 12 wolves and 60 dogs (from 14 different breeds)
were sequenced in this study. The team detected over 3.7 million single
nucleotide polymorphisms, over 1.7 million of which were unique to domesticated
dogs. They searched for reduced heterozygostity—a measure of how recently the polymorphism
developed—however, the researchers did note that it is difficult to distinguish
allele fixations caused by genetic drift from those alleles chosen by natural
or artificial selection.
Thirty-six “domestication regions,” which included 122
separate genes, were identified by the researchers. Several of these genes explain
differences in brain development and thus behavioral changes.
However, three genes involved in the breakdown and uptake of
starches were found to differ significantly between the wolf and dog DNA. Dogs
carry many more copies than wolves of the alpha-2B-amylase encoding gene which
in involved in the breakdown of starches. In addition, an extension of the MGAM
gene is likely another adaptive mutation that allowed dogs to adopt a more
omnivorous diet (this extended gene is also found in herbivorous and omnivorous
animals like rabbits and rats). And finally, changes in the SGLT1 gene are
responsible for higher rates of glucose uptake in dogs than wolves.
The mutations in these genes allow dogs to leave behind some
of their carnivorous tendencies (e.g. your faithful pooch views the biscuit and
not your hand as food) and also help their digestive systems cope with “human
food” like roots and grains.
There are still questions about whether these genetic
adaptations came about as a result of a scavenging lifestyle or selective
breeding of wolves, and it is likely that further studies will focus on pinning
down the exact timing of these genetic changes that led to the co-evolution of
man and dog.
Link to original article in Nature
Word count: 379
This is a really interesting topic because domestic animals are so prevalent today, and the fact that a handful of mutations could played a role that led eventually to canine domestication. However, I don't agree completely with the 'starches theory' because I believe there was whole host of other factors (human artificial selection, increased canine cognition, trade-off for the canines to live with humans, etc.).
ReplyDeleteI think you are absolutely right that there are other factors that likely played a role in this coevolutionary step. In addition to the starches theory, the paper also mentioned cognition differences and other brain development differences but those topics had already been covered in previous literature. However, I believe it was their intention to highlight differences that were previously unknown.
DeleteThis is a great topic! I am curious to see what future studies will reveal. Did you come across studies that revealed other major gene differences, beyond the three you focus on in your post?
ReplyDelete-Mary Morales
Does this also help to explain differences between the many dog breeds, or is that solely due to selective breeding? Is it possible that the differences in dog breeds arose from other differences?
ReplyDeleteThe paper did not talk about the differences between the dog breeds other than the fact that they used multiple different breeds to represent some of the genetic variation. I would guess that the different dog breeds, like you suggest, are really a result of years of selective breeding.
DeleteI'm a bit confused as to the framing of your argument. It almost seems like you say that the processing of starches is what led to speciation and the divergence of wolf and dog. However, isn't it more likely that the ability to better process starch evolved after speciation, when the dog's environment and consumption became closer to that of man's? It would also be interesting to analyse the selective pressures that exist for domesticated animals.
ReplyDelete-Tom Xia
Yes it does seem to be a sort of "chicken and egg" argument, but I think the article was focusing on the beginning of the relationship between man and wolf being facilitated by a beneficial mutation (the ability to digest starches).
DeleteThis is so interesting! I wonder if breeds of dogs that are known to have higher rates of human attack have less of these starch digesting enzymes and if they do tend to be more carnivorous. Could that be the reason that they are more aggressive?
ReplyDeleteI agree with Tom that the evolution of higher starch genes is probably a result of domestication and not the cause of it. It seems that once humans were able to train certain dogs, the ones that were best suited to life with humans were best fit to reproduce can pass on starch genes.
ReplyDeleteI think that this is a very interesting topic. I'd like to learn more about how the speciation of dogs came from wolves. Is it possible that the domestication of dogs by humans is what lead to this increase in starch enzymes. I always thought that the speciation of dogs came from a less molecular source and instead was because of the way humans began to train them.
ReplyDeleteWow! this was interesting! I would like to know more about the effects of selective breeding on wolves and how they could have contributed to the difference between dogs and wolves. I wonder if the environment had anything to do with the difference. If some wolves ended up in a habitat with no meat, which made them adapt to new kinds of food.
ReplyDeleteThis article was very interesting, and it was similar to another article I read about the coevolution between dogs and humans. However, this has a different perspective on how dogs came to be man's best friend. Wouldn't this somewhat imply that we would be able to domesticate any animal as a pet, as long as they can digest starches? The other argument that I had read supported the hypothesis that it had more to do with the evolution of their social behavior.
ReplyDeleteIt's striking that genetic makeup can make a difference when it comes to domestication. I wonder if there will be a time when scientists will be able to tame wild animals through genetic manipulation.
ReplyDeleteI have always been curious about the domestication of wolves into dogs, and this article did a very good job of explaining this. Who would have thought that it would be genes encoding for the breakdown of starches and sugars that would have been the most different between wolves and dogs!
ReplyDeleteWhat is most interesting to me about domestic dog breeds is that some are very wolf-like such as the tamaskan, but can breed with something as dissimilar as a chihuahua.
ReplyDelete