Some interesting work has been published this month in Nature and reported in various blogs and Journals. It is work that gives more evidence to support the fact of evolution. A team of Swedish Scientists led by evolutionary geneticist Erik Axelsson from Uppsala University have identified genetic changes that could have been responsible for the transformation of wild wolves, into the ancestors of our beloved pet dogs. The paper asserts that this is an evolutionary event that arose from the birth agriculture. This means that the dog’s evolutionary history is very much tied in with our own.
The domestic dog’s history goes back between 10,000 – 12,000 years, in evolutionary terms a blink of an eye. The story is not just about the taming of wolves, it also required genetic changes. Cofty has in his “Greatest Show on Earth” thread described the Russian experiment where silver foxes were artificially selected for their friendliness and a pleotropic effect was seen whereby selecting for friendliness also affected physical characteristics such as colour, the growth of tail and ear shape.
This study compared the genome sequences of dogs and wolves to consider whether there has been a change in dietary habits. It has been suggested that a key step in the domestication of dogs was their ability to digest starch-based food, in contrast to poor starch digestion by the entirely carnivorous wolves. For this to occur enzymes such as amylase and maltase would have to be produced and we now know that this would require new gene sequences being created or turned on
In the study, Axelsson and his colleagues pooled genome sequence data from 60 dogs and 12 wolves and looked for differences as well as regions in the dog genome that were nearly identical in all dogs. The team identified 36 genomic regions that may explain differences in behaviour and food habits between wolves and dogs. Nineteen of these genomic regions contain genes involved in brain functions, and several other genes play key roles in starch digestion.
The differences in some of these 36 genetic regions make dogs different from wolves, this mean this is genuine “macro” evolution, a sign of speciation, all occurring in very short period of time.
With regard to the differences in the domestic dog’s ability to digest starch this is a completely new and unexpected discovery, It gives evolutionary biologists a great big hint as how domestication may have started. Evolutionary biologists had in the past suggested that the domestication of dogs had occurred through natural selection as wolves were drawn to early human settlements for morsels of leftover food. Natural selection would favour wolves that were less shy and did not run away when humans approached them would have been more efficient in scavenging food.
However, to be efficient scavengers those wolves would also need to be able to efficiently digest the food that was being discarded by those early farmers. The ability to process starch would provide a much stronger advantage over the wolves that could not, since starch was a key constituent of food that emerged with farming. Only wolves that made good use of leftovers of food such as cereal crops, survived to become ancestors of domesticated dogs.