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Dog evolved ‘on the waste dump’

pub­lished 23 Jan­u­ary 2013 | mod­i­fied 23 Jan­u­ary 2013
Grey wolfA study of sci­en­tists at SciL­ife­Lab Upp­sala and the Broad Insti­tute show that the genome of dogs and wolves dif­fer in some impor­tant ways. There are cru­cial dif­fer­ences in genes for the devel­op­ment of the brain, but also an adap­ta­tion of the diges­tive sys­tem to more resem­ble that of humans.

It is still shrouded in mys­tery when and where dogs and their wild ances­tors the wolves went sep­a­rate ways, but pre­sum­ably it hap­pened more than 10,000 years ago some­where in Asia. It may have started by humans seek­ing out wolves’ dens to catch and tame wolf pups. Alter­na­tively, the wolves them­selves may have come closer to humans to look for food in the scrap heaps that became com­mon when humans set­tled.

This shows how changed behav­iour as well as diet has been of impor­tance to dogs’ adap­ta­tion to a life close to humans.
pro­fes­sor Ker­stin Lindblad-​Toh, direc­tor of SciL­ife­Lab Upp­sala »

In the study pub­lished online in the Jan­u­ary 23 issue of the sci­en­tific jour­nal Nature the researchers have com­pared the genomes in a large num­ber of dogs and wolves, and mapped areas of the genome that show clear dif­fer­en­ti­a­tion between the two groups. The results show that dogs went through sev­eral devel­op­men­tal steps that adapted their diges­tive sys­tem to a diet richer in starches than that of wolves.

Starch, the most com­mon car­bo­hy­drate in our food, is bro­ken down into sugar in dogs’ intestines and then trans­ported out into the blood in a process that involves three dif­fer­ent steps. The Upp­sala researchers found sig­nif­i­cant changes to all parts of this process in dogs.

Most strik­ing was that the dog genome gen­er­ally con­tains many times more copies of the gene, amy­lase, that car­ries out the first step of the break­ing down of starch”, says Erik Axels­son, lead author and researcher at SciL­ife­Lab Upp­sala and the Depart­ment of Med­ical Bio­chem­istry and Micro­bi­ol­ogy, Upp­sala Uni­ver­sity.

Our results show that it was cru­cial for the sur­vival of early dogs to be able to live on food that largely con­sisted of veg­eta­bles, such as root veg­eta­bles and cere­als”, says Erik Axels­son. “This in turn indi­cates that the domes­ti­ca­tion of dogs may be con­nected to the human devel­op­ment of agri­cul­ture and that it was on the scrap heaps of early set­tle­ments that the first steps of the devel­op­ment of dogs took place.”

A sim­i­lar, but per­haps less exten­sive, adap­ta­tion to increased intake of starches has been found in us humans, which reflects how tightly linked the evo­lu­tion­ary his­tory of humans and dogs are. This means that by study­ing the effect of genetic changes dur­ing the domes­ti­ca­tion of dogs we can also learn about our own species’ adap­ta­tions to the envi­ron­ment and related dis­eases.

Apart from the clear adap­ta­tion of dogs’ diges­tive sys­tem, the researchers also found many dif­fer­ences in genes that affect how the brain is devel­oped. Sev­eral of these changes are likely expla­na­tions to why dogs behave dif­fer­ently to wolves. “It was excit­ing to see that half of the domes­ti­ca­tion indi­ca­tors in the genome point to genes that have to do with the devel­op­ment and func­tion of the brain”, says pro­fes­sor Ker­stin Lindblad-​Toh, senior author and direc­tor of SciL­ife­Lab Upp­sala, and sci­en­tific direc­tor of ver­te­brate genome biol­ogy at the Broad Insti­tute.

The research group will now con­tinue to study in detail how the genetic adap­ta­tions affect dogs’ behav­iour.

The above news item is reprinted from mate­ri­als avail­able at Upp­sala Uni­ver­sity. Orig­i­nal text may be edited for con­tent and length.
(Source: Upp­sala Uni­ver­sity News, 23.01.2013)
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