|Feature Article - July 2013|
|by Do-While Jones|
An evolutionary study of dogs gives us something to chew on.
Last January, a study published in the respected journal, Nature, claimed that table scraps turned wolves into dogs.
A study published in Nature today finds that dogs possess genes for digesting starches, setting them apart from their carnivore cousins — wolves.
The authors say the results support the contentious idea that dogs became domesticated by lingering around human settlements. “While it’s possible that humans might have gone out to take wolf pups and domesticated them, it may have been more attractive for dogs to start eating from the scrap heaps as modern agriculture started,” says Kerstin Lindblad-Toh, a geneticist at Uppsala University in Sweden, who led the work.
Canine-domestication researchers agree that all dogs, from beagles to border collies, are the smaller, more sociable and less aggressive descendants of wolves. But neither the time nor the location of the first domestication is known: fossils place the earliest dogs anywhere from 33,000 years ago in Siberia to 11,000 years ago in Israel, whereas DNA studies of modern dogs put domestication at least 10,000 years ago, and in either Southeast Asia or the Middle East. Many researchers believe that dogs were domesticated more than once, and that even after domestication, they occasionally interbred with wild wolves. 1
We note in passing that, as usual, the fossil evidence does not agree in time or place with genetic studies. There’s nothing new about that.
Here is the abstract of the study that was published in Nature.
The domestication of dogs was an important episode in the development of human civilization. The precise timing and location of this event is debated and little is known about the genetic changes that accompanied the transformation of ancient wolves into domestic dogs. Here we conduct whole-genome resequencing of dogs and wolves to identify 3.8 million genetic variants used to identify 36 genomic regions that probably represent targets for selection during dog domestication. Nineteen of these regions contain genes important in brain function, eight of which belong to nervous system development pathways and potentially underlie behavioural changes central to dog domestication. Ten genes with key roles in starch digestion and fat metabolism also show signals of selection. We identify candidate mutations in key genes and provide functional support for an increased starch digestion in dogs relative to wolves. Our results indicate that novel adaptations allowing the early ancestors of modern dogs to thrive on a diet rich in starch, relative to the carnivorous diet of wolves, constituted a crucial step in the early domestication of dogs. 2
There is some good science here. They have compared dog genes to wolf genes in order to discover what causes the differences between wolves and dogs. Genetic differences result in physical differences. It is important to discover those relationships because they could lead to practical medical advances.
There is also bad science here. They wasted time and money trying to guess how evolution caused the changes, ignoring the possibility that dogs and wolves might not actually have a common ancestor. It is also a waste of time to argue about whether or not people domesticated wolves by deliberately feeding them, or failing to keep them out of their garbage dumps.
The good science tells us there is a genetic reason why dogs can digest some kinds of food that wolves can’t.
Regardless of how dog domestication started, several characteristics separating modern dogs from wolves, including reduced aggressiveness and altered social cognition capabilities, suggest that behavioural changes were early targets of this [evolutionary] process. Dogs also differ morphologically from wolves, showing reduced skull, teeth and brain sizes. 3
Why would it be advantageous for dogs to be less aggressive and have smaller brains and teeth? Evolutionists will insist that it must be advantageous; otherwise, these characteristics would not have evolved. Therefore, a story must be concocted to show why it is better to have a smaller brain and smaller teeth.
The study explained that dogs use a three-step process to digest starch. Here is part of what they said (with the long, technical details left out):
The breakdown of starch in dogs proceeds in three stages: [which involve amylase activity.] …
Whereas humans have acquired amylase activity in the saliva via an ancient duplication of the pancreatic amylase gene, dogs only express amylase in the pancreas. 4
They claim that when farming replaced hunting, dogs and humans both developed an improved ability to digest starch, allegedly through different evolutionary pathways.
The results presented here demonstrate a striking case of parallel evolution whereby the benefits of coping with an increasingly starch-rich diet during the agricultural revolution caused similar adaptive responses in dog and human. 5
The assumption is that ape-men and wolves initially ate only meat, but both independently evolved the ability to digest starch through different genetic mutations, both of which were favored by natural selection, resulting in modern humans and dogs, which ate the same food together, causing dog to become man’s best friend.
The underlying assumption is that wild wolves became tame dogs. Isn’t it possible that tame dogs became wild wolves?
How can you prove that dogs evolved from wolves by gaining the ability to digest starch, instead of wolves devolving from dogs by losing the ability to digest starch and having to hunt for small animals to eat?
The fact that dogs and wolves are similar does not prove that both had a common ancestor; but just for the sake of discussion, let’s assume they did. Is it not more logical to believe that a random mutation to DNA caused a loss in the ability to digest starch than to believe that a random mutation to DNA created the ability to do so?
Wolves don’t eat starch. Why is that? How do they know they can’t digest it? Appetite is a marvelous thing. Appetite motivates us to eat things we can eat, and makes inedible things unappealing. A ripe peach will make your mouth water. An unripe peach, or a cotton ball, won’t.
So, not only would the ability to digest starch have to evolve, the appetite for starch would have to evolve as well. What good is the ability to digest starch if the taste is so unappealing the animal never puts it in its mouth?
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Ewen Callaway, Nature, January 2013,
“Dog's dinner was key to domestication”, http://www.nature.com/news/dog-s-dinner-was-key-to-domestication-1.12280
2 Axelsson, et al., Nature, 23 January 2013, “The genomic signature of dog domestication reveals adaptation to a starch-rich diet”, http://www.nature.com/nature/journal/v495/n7441/full/nature11837.html