The analysis turned up 36 regions, with 122 genes in all, that may have contributed to dog evolution, the team reports online today in Nature. Nineteen of these regions contain genes important for the brain, eight of which are involved with nervous system development, which makes sense given the importance of behavioral changes in the transition to becoming man's best friend, Axelsson notes.Nature (2013) doi:10.1038/nature11837
More surprising were genes for digesting starch. Dogs had four to 30 copies of the gene for amylase, a protein that starts the breakdown of starch in the intestine. Wolves have only two copies, one on each chromosome. As a result, that gene was 28-fold more active in dogs, the researchers found. More copies means more protein, and test-tube studies indicate that dogs should be fivefold better than wolves at digesting starch, the chief nutrient in agricultural grains such as wheat and rice. The number of copies of this gene also varies in people: Those eating high carbohydrate diets -- such as the Japanese and European Americans -- have more copies than people with starch-poor diets, such as the Mbuti in Africa. "We have adapted in a very similar way to the dramatic changes that happened when agriculture was developed," Axelsson says.
The genomic signature of dog domestication reveals adaptation to a starch-rich diet
Erik Axelsson et al.
The domestication of dogs was an important episode in the development of human civilization. The precise timing and location of this event is debated1, 2, 3, 4, 5 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 domestication6. 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.
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14 comments:
Fascinating. This is the most definitive genetic evidence I've seen to date for a true species or subspecies distinction betweeen wolves and dogs.
Recently, it had seemed as if the case for anything more than a breed distinction between the two was pretty weak, but this changes the story in a way paralleling the lactose tolerance gene in humans.
Query if this dates to the Neolithic or to earlier. Flour use by modern humans actually predates the Neolithic by tens of thousands of years, so starch consumption genes wouldn't have to be Neolithic.
Makes me think of animals being attracted to human food scraps.
Query if this dates to the Neolithic or to earlier. Flour use by modern humans actually predates the Neolithic by tens of thousands of years, so starch consumption genes wouldn't have to be Neolithic.
I'd say the question is whether humans have produced an exploitable surplus of flour for tens of thousands of years. The answer is probably, no.
That said, I don't see that these new findings provide a compelling reason to believe dogs were domesticated during the Neolithic. It seems eminently reasonable to assume that a Paleolithic butcher site would attract canid scavengers, should any be present. Successful exploitation of such a niche economy might have selected for at least some of the neurological differences seen here in dogs.
If dogs were already living with us at the dawn of the Neolithic, then a substantive change in our diet would have put selective pressure on domesticated or semi-domesticated canines as well.
Starch obviously had little to do with early dog domestication. Grains started to be utilized on a grand scale about a factor of three later than early dog domestication. And UP and Mesolithic people used dogs to widen their meat intake (and for other reasons), if anything.
Also, consider the fact that dogs were already present in the Americas before European contact. Those animals were likely domesticated in a Paleolithic context and it is difficult to see why a capacity to digest starches might provide a significant advantage at such an early date.
It would be interesting to see whether those ancient American dogs could efficiently exploit a starch-rich diet. If not, then that might explain why they were apparently wholly replaced by European lineages, post-contact.
Va_Highlander, the Cherokee tribe had dogs pre-Columbus; and they also grew vast fields of corn (or maize) which was their main diet staple -- long before 1492.
The Earth is so old, that Agriculture may have come and gone ~many times throughout history, and among diverse tribes, due to climatic, environmental and social pressures.
(May I also point out, that the pre-Columbian Cherokees strictly forbade the practice of ~cannibalism in any form. Punishment was death of the offender within the same day caught in the act.)
When are 'they' going to realize that dogs are coprophagic. Even today, in places where humans defecate in the open on the ground, dogs clean up. It wasn't starch.
shenandoah,
Not quite sure what you're attempting to say. While cannibalism, or claims of cannibalism, are interesting, in an anthropological or historical context, I fail to see the relevance, here. Other Native Americans were worried about cannibalism as well. See the legend of the wendigo, for instance.
A quick Google search tells me that the oldest domestic dog remains in the New World appear to date from about 12,500 years, before present. This is long before the Cherokee and long before the earliest agricultural developments on these shores. Moreover, it is known that ancient American dogs were more closely related to Old-World dogs than they were to New-World wolves, so there is little doubt that the ancestors of these canines were brought here by a Paleolithic immigrant population, whether Clovis or some other.
To your other point, while it seems obvious that agriculture had multiple origins world-wide, there seems no evidence, or at least none that I've seen, suggesting that agriculture developed more than once and was subsequently lost. Barring an extinction event, such a thing makes little sense. The advantages of agriculture as a subsistence strategy are just too overwhelming.
Va_Highlander, "Barring and extinction event..."
Are you aware that the American continents were once home to such now extinct (here anyway) animals as wooly mammoths, wild (pre-domestication) horses, camels, saber-toothed tigers, certain kinds of marsupials, etc.? And that very old American newspapers hold dozens of independent accounts of skeletal remains and mummies found of now extinct types of Humans?
Also, can you explain how you figure the domestication of American dogs 12,500 yrs ago was "way before the Cherokee and... before American Agriculture"? How do you know that, in other words? Also, how do you know that the Cherokee dogs prior to 1492 were not the same or similar animals to the ones first domesticated ~12,000 yrs ago?
(As for the topic of cannibalism, I just sometimes like to remind others that it was not some universal culturally accepted habit among all tribes. I just took the opportunity to throw in that dietary tidbit, since we were on the subject, and had that statement in parentheses for that reason.)
"Are you aware that the American continents were once home to such now extinct (here anyway) animals as wooly mammoths, wild (pre-domestication) horses, camels, saber-toothed tigers, certain kinds of marsupials, etc.?"
Yes, and there were some species of dinosaur, too. Before that, 420 million years ago, there were even trilobites skittering about in the warm, tropical seas of Bath Co, Virginia. What is your point?
"And that very old American newspapers hold dozens of independent accounts of skeletal remains and mummies found of now extinct types of Humans?"
Actually, no, they don't, at least none that will withstand close examination. More generally, if you are forced to cite old newspaper accounts as evidence in support of your claim, you have departed the realm of scientific discussion for a world of idle fancy. I shan't be following you.
'Also, can you explain how you figure the domestication of American dogs 12,500 yrs ago was "way before the Cherokee and... before American Agriculture"?'
Quite easily, yes. Modern archeology is rather good at establishing reasonably accurate dates for such things. And being good little amateur scientists, we do not just make stuff up without evidence. Therefore, since there is no evidence whatsoever of any Cherokee-like people existing 12,500 years ago, and no evidence of agriculture anywhere in the Americas at such an early date, I can make such statements with confidence and from a firm, scientific footing.
"Also, how do you know that the Cherokee dogs prior to 1492 were not the same or similar animals to the ones first domesticated ~12,000 yrs ago?"
Why should I think they would be different?
Neither I nor anyone else is suggesting that ancient American dogs were domesticated ~12,000 ybp. What I said was that the oldest domestic dog remains found in the New World date to about 12,500 years ago. Since the Americas were populated no later than 13,000 ybp, and since modern genetics informs us that these canines were more closely related to Old-World dogs than they were to New-World wolves, we are forced to conclude that the ancestors of these ancient dogs were domesticated in the Old World, before they were brought to the Americas.
"Therefore, since there is no evidence whatsoever of any Cherokee-like people existing 12,500 years ago, and no evidence of agriculture anywhere in the Americas at such an early date, I can make such statements with confidence and from a firm, scientific footing."
Sorry, but lack of evidence is not conclusive proof of your claim.
http://upload.wikimedia.org/wikipedia/commons/thumb/e/ef/Hopewell_Exchange_Network_HRoe_2010.jpg/300px-Hopewell_Exchange_Network_HRoe_2010.jpg
Here is just one rather simplistic map of the quite real and very well documented Stone Mound systems of North America, which were left by the ~predecessors (ie the ~ancestors, in some cases) of Cherokees and other more contemporary tribes.
IF Neanderthal DNA can persist within the genomes of "modern" Humans, THEN it follows that the ancient Humans who created those Mounds' DNA probably ~also persists in at least some modern Native American types of Humans. Just because you have no concrete evidence to your own intellectual satisfaction, does not rule out that fact.
You still haven't convinced me that the dogs Cherokees owned prior to 1492 did not eat plenty of starch in the form of maize or corn. That is basically what you said, in your first comment here; that North American aboriginal dogs were owned by Hunter-gatherers who did not engage in Agriculture. That is a false statement, as I have pointed out already.
Sorry, but lack of evidence is not conclusive proof of your claim.
My claim isn't based on a "lack of evidence". The genetic study of ancient American dogs was done at UCLA:
"Humans Brought Domesticated Dogs to New World More Than 12,000 Years Ago"
I see no reason to doubt their conclusions.
As for the rest of my statement, in order to reasonably object, you must produce a compelling argument for the existence of agriculture in North America at the end of the last Ice Age, beginning with a sober discussion of why the idea isn't as silly as it first appears. You must produce a compelling argument for the existence of the Cherokee as a distinct people at such an early date, when even the fanciful stories that linguists tell suggest that the Cherokee did not split from the Iroquois until the Middle Archaic or later.
Obviously, in the mean time I won't be holding my breath.
The Hopewell trade network has no relevance to this discussion and likely predates the Cherokee migration by at least 500 years. I don't know whether the ancestors of the Cherokee were part of Hopewell. I doubt that you know, either. The stone mounds of North America are a separate issue and not necessarily related to either Hopewell or the Cherokee.
IF Neanderthal DNA can persist within the genomes of "modern" Humans, THEN it follows that the ancient Humans who created those Mounds' DNA probably ~also persists in at least some modern Native American types of Humans. Just because you have no concrete evidence to your own intellectual satisfaction, does not rule out that fact.
I suspect that you lost the plot some time ago, since it's wholly irrelevant to this discussion whether there are descendants of the mound builders alive, today. My "intellectual satisfaction" has nothing to do with it.
You still haven't convinced me that the dogs Cherokees owned prior to 1492 did not eat plenty of starch in the form of maize or corn. That is basically what you said, in your first comment here; that North American aboriginal dogs were owned by Hunter-gatherers who did not engage in Agriculture.
Nope.
I said that the ancestors of pre-Columbian dogs were domesticated in a Paleolithic context, before they were brought to the Americas. All the evidence before me supports that claim and there is nothing contradicting it. I said nothing whatsoever about who subsequently owned the descendants of those first canines.
http://www.nps.gov/seac/benning-book/ch06/f041.jpg
"Figure 41: The Missippian culture centered around *agriculture* and earthen monuments."
http://www.nps.gov/seac/benning-book/figures.htm
http://www.nps.gov/seac/benning-book/ch06/f051.jpg
Mississippian Dog Effigy in pottery.
http://en.wikipedia.org/wiki/Mississippian_culture
Believed to have existed mainly in the time period between 800 CE and 1500 CE... But who knows for how long or for how many 'extinct' civilizations Agriculture was the dietary cornerstone of North America?
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