dog breeds on a dog's purpose

a world without dogs sounds like no fun atall. but many of the hundreds of dog breeds weknow today are only a few centuries old. and, according to current research, if yougo back in time at most 34,000 years -- dogs, as we know them, didn’t even exist! even though we know that modern dogs and modernwolves share a wolf ancestor, no one’s sure exactly how dogs were first domesticated…or even when. but we do know that at some point, dogs evolvedfrom mostly ignoring humans to wanting to be best friends with us. that process of domestication came with consequences.some of them you’d expect, like dogs becoming

tamer over time. and others are just… strange. for instance, there’s a trait that dogsshare with other domesticated animals, that even darwin thought was weird: lots of dogbreeds have floppy ears. evolutionarily, this doesn’t make much sense.it’s a result of deformed ear cartilage, and it can actually make it harder for a dogto hear. so why would we breed dogs to have deformedears? well, we didn’t, at first. at least, noton purpose. instead, floppy ears seem to have a lot todo with other traits that domesticated animals

have -- like patches of white fur, and adorablelittle faces that retain their juvenile features into adulthood. according to a new hypothesis, it turns outthat in the process of domesticating dogs, we might have actually been affecting someof their stem cells. in a dog embryo, there’s a group of stemcells called the neural crest. and these cells are responsible for forming a specific setof physical features -- like the dog’s coat, and the structure of its face, and its adrenalglands. and according to this new research, a lotof the features that we associate with tameness may actually come from changes that have beenmade to this neural crest.

the earliest dogs may have been less aggressivebecause they had smaller adrenal glands. so when early humans bred for tameness, thedogs probably also ended up with changes to other traits that are controlled by the neuralcrest -- like floppy ears, and the faces with more juvenile features, such as smaller jaws. so basically, by domesticating dogs, we mayhave ended up selecting for mutations in their stem cells that made them less like wolvesand more like the animal that’s probably sleeping in your living room right now. but domesticating dogs has had other usefulside effects, too. for example, dogs are a whole lot better thantheir wild cousins at digesting starch.

a study published in 2013 analyzed the genomesof 12 wolves, and 60 dogs of different breeds. the researchers were looking for genetic differencesthat showed up in all of the dogs, but none of the wolves. they found changes in 36 regions of all ofthe dogs’ dna. some of the results were somewhat predictable,like changes to genes that are involved in brain development, which account for how friendlyand tame dogs can be. but they also found something that they didn’texpect: the dogs had three genetic variations that helped them digest starch. this fits with the theory that dogs firststarted to be domesticated as many humans

settled down to an agrarian life. at some point, hungry wolves might have startedventuring into human settlements and eating their leftover starchy food… something thata lot of modern dogs seem to be into as well. the wolves that were best able to digest thestarch were better fed, so they survived to reproduce. and speaking of things that dogs are reallyinto, you know how dogs really like chewing on bones ... but it seems to take them foreverto actually finish eating one? well, that has a lot to do with their ancestry,too. wolves eat meat. and they’re really intothe stuff -- it doesn’t matter how delicious

you think your pie is, a wolf is going topick the steak any day. so they’ve got really sharp teeth that areperfect for tearing apart flesh, and powerful jaws that polish off a bone pretty quickly,especially if they’re looking to get to the marrow inside. but even though dogs inherited wolves’ desireto gnaw on bones, they have smaller jaws and a less powerful bite. which means that it takes them a whole lotlonger to finish a bone, if they can even make a dent in it at all. but if you’ve ever seen a dog chewing ona bone… it doesn’t seem like they mind

how long it takes to finish it. thanks for watching this episode of scishow.if you want to keep getting smarter with us, just go to youtube.com/scishow and subscribe.