After implantation, the tissue developed blood vessels and became integrated into neuronal networks in the animals’ brains.
As wolves became domesticated, their genes adapted to a starch-rich diet of human leftovers.
January 23, 2013|
WIKIMEDIA, ALLISON LAINGA comparison of the full genomes of dogs and wolves revealed many changes that accrued as wild canines evolved into man’s best friend. Unsurprisingly, many of these differing regions regions affect the brain, and may explain the different temperaments of wolves and dogs. But the comparison, published today in Nature also pinpointed several regions that are involved in digestion, including genes that help to break down starch.
“This supports the idea that proto-dogs evolved new digestive adaptations to rely on the edible by-product of the agricultural revolution – garbage,” said Brian Hare from Duke University, who studies animal domestication and was not involved in the study.
Israeli fossils and genetic studies date dog domestication to around 10,000 years ago, coinciding with the Agricultural Revolution, when humans went from nomadic hunter-gatherers to farming and living in settlements. Some scientists have suggested that wolves were attracted to dump sites near these early settlements and scavenged on leftovers from vegetables and cereal plants. “Dogs may have domesticated themselves by seeking out humans, to eat from their scrap-heaps,” said Kerstin Lindblad-Toh from Uppsala University, who led the new research.
Lindblad-Toh led the team that published the full domestic dog genome back in 2005. With that project completed, she turned to the evolutionary history of our canine companions. “While a lot of studies have looked at the when and where of dog domestication, little has been done to understand how this happened on a genomic level,” she said.
Together with Erik Axelsson, Lindblad-Toh sequenced the full genomes of 12 wolves from around the world, as well as 60 dogs representing 14 diverse breeds. They searched for signatures of domestication by looking for sequences that that showed the greatest differences between dogs and wolves, or for sequences that were consistent across dog breeds but varied in wolves.
The team eventually came up with a list of 36 regions, containing a total of 122 genes. Half of these regions contained brain genes. “This is not surprising,” said Lindblad-Toh. Compared to wolves, dogs are less aggressive, more sociable, less afraid of humans, and better able to read our behavioral cues.
Six other regions, containing 10 genes, were involved in digesting fat and starch. Specifically, dogs carry extra copies of the gene for amylase—an intestinal enzyme that cuts starch into maltose—and now produce 28 times more of the protein than their wolf counterparts. Dogs also produce 12 times more maltase-glucoamylase, which converts maltose into sugar, thanks to several mutations in the gene for this enzyme. Mutations in a third gene—SGLT1—improved the function of a protein that absorbs the sugar through the gut.
“They have made a very convincing case for the involvement of starch digestion in the evolution of the dog,” said Ben Sacks from the University of California, Davis, who was not involved in the study. (Interestingly, some of the changes observed in dog digestion have parallels in humans. As we moved from hunting meat and gathering berries to farming grains and vegetables, we, too, duplicated our amylase gene, which some have seen as an adaptation to a starch-rich diet.)
Rodney Honeycutt, an evolutionary geneticist from Pepperdine University, was also impressed by the data, but noted that it is unclear when these changes took place. “The ability to digest starch effectively would not necessarily make an animal docile, and may have occurred subsequent to domestication,” he said.
But Lindblad-Toh argued that mental and digestive changes are likely to go hand in hand. “Dogs that were not afraid of people and that could adapt to a more omnivorous diet may have been the ones that stayed and were domesticated,” she said.
E. Axelsson et al., “The genomic signature of dog domestication reveals adaptation to a starch-rich diet,” Nature, 2013: doi:10.1038/nature11837, 2013.
January 24, 2013
Rudyard Kipling's Just So Stories talked about Wild Dog taking food from the First Woman - perhaps he knew more about DNA, evolution and domestication than we thought. We've written about the DNA changes in the dog and the wolf at http://www.genome-engineering.com/how-the-dog-and-its-genes-came-out-of-the-wild-woods%E2%80%A6.html
January 24, 2013
"As we moved from hunting meat and gathering berries to farming grains and vegetables, we, too, duplicated our amylase gene, which some have seen as an adaptation to a starch-rich diet.)"
I hope the impractical paleo-diet proponents are reading this. But then again why would they be on a science website? They have Robb Wolf feeding them the pseudo version.
January 24, 2013
The difference in the epigenetically-effected genetically predisposed development of the brain and behavior of adult wolves and dogs can be attributed to exploration using only olfaction (sans vision and hearing) during the first two weeks of life in wolf pups. The downstream effects of acquired nutrients and pheromones on subsequent brain development and behavior are hormone-organized and hormone-activated by the epigenetic effects of nutrients and pheromones, as they are in all vertebrates and invertebrates. Moreover, “Olfaction and odor receptors provide a clear evolutionary trail that can be followed from unicellular organisms to insects to humans.”
However, you can skip the systems biology and molecular mechanisms common to all species. It's still clear that the differences in wolves and dogs result from the downstream effects of olfactory/pheromonal input on genetically predisposed species-specific behaviors.
Dr. Honeycutt notes, for example, that "The ability to digest starch effectively would not necessarily make an animal docile..." However, the concept that is extended here is the epigenetic tweaking of immense gene networks that solve problems through the exchange and the selective cancellation and modification of signals.
It is now clearer how an environmental drive evolved from that of food ingestion in unicellular organisms to that of socialization in insects and nutrient-dependent pheromone-controlled behavior in mammals, which explains the differences between wolves and dogs. Thus, while you cannot explain domestication via diet alone, you can explain both speciation and domestication via the metabolilsm of nutrients to species-specific pheromones, which also epigenetically effect hormones that affect behavior.
February 14, 2013
Hurray! Good to read commonsense observations!
..."their genes adapted to..." :
(“Reversible marks on the genome allow honeybees to swap between lives as nurses and foragers.”?
Look again. Flip From Head- To Feet- Standing…)
(New Science of Consciousness ? Look underneath the AcademEnglish verbiage…)
Genetics Is Progeny Of Culture
It evolves from survival challenges, from natural selection challenges !!!
Adnauseam Genetics Is Progeny Of Culture
Darwin and Pavlov: it is culture, the ubiquitous trait of all mass formats’ reaction to circumstances, that modifies genetic expressions…
Update Comprehension Of Culture-Genetics
http://universe-life.com/2012/07/20/upd ... -genetics/
The neural system, including the brain, was evolved by unicells communities (cultures) to react to, exploit, the environments for survival-natural selection.
Tree's leaves genetically different from its roots
http://www.nature.com/news/tree-s-leave ... #/comments
The cultures of the roots and leaves, their survival reactions to and exploitation of circumstantial environments, are different, hence their different genetics.
Common sense is the best scientific approach. Plain and simple.
Genome Evolves By Culture, Natural Selection, Not Randomly
Rate of de novo mutations and the importance of father’s age to disease risk
http://www.nature.com/nature/journal/v4 ... 11396.html
RNA nucleotide genes are ORGANISMS, life’s primal ORGANISMS.
Genomes are template ORGANISMS evolved and continuously updated by the RNAs for carrying out their - RNAs’ - natural-selection tasks.
All life’s activities originate and evolve for the survival of the RNAs.
THIS is Darwinian evolution.
Modified RNAs expressions are NOT random mutations. Some of them are caused accidents, but not random. Apply Darwinism to them.
There is no randomness in the universe that evolves from all inert mass, singularity, to all moving mass, energy, and probably back again.
Now, after a century of strangled Enlightenment, it’s time to restructure science plans, policies and budgets.
The viable future of humanity is not with natural selection, but with Scientism, the follow up of Enlightenment.
Dov Henis (comments from 22nd century)
Tags: genetic mutations, RNA genes life’s primal organisms, genomes template organisms, natural selection