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Wherein we discover what is living in Paris Hilton's purse.


Facebook: http://www.facebook.com/thebrainscoop

The Brain Scoop is written and hosted by:
Emily Graslie

Created by:
Hank Green

Written, Directed, Edited, Animated, and Scored by:
Michael Aranda

Special thanks to Hank and Katherine Green, and Brandon Neumayer for letting us film Lemon and Newton!

And ultra thank-you to Martina Šafusová, Diana Raynes, Katerina Idrik, Barbara Velázquez, Adam Wojniłło, Tony Chu, Seth Bergenholtz, and Gaia Zaffaroni for providing the transcriptions!
Today we're gonna talk about domestication. Domestication is the process in which humans selectively breed for a certain characteristic in a plant or animal.

In the last 40,000 years or so, we've domesticated horses, and cows, and sheep, and goats, and pigs, and guinea pigs, and ferrets, and furbys, and honeybees, and cockroaches, and skunks, and over 100 other species.

It's not just limited to animals either. We've domesticated plants and fungi for food and cultivation of crops, and for also giving flowers to your mother.

One of the first animals to be domesticated, as you may know, was the dog about 30,000 years ago. According to an article by National Geographic, some wolves figured out that if they were friendly to humans they would have a much better chance of survival than their aggressive and hostile packmates. Food was scarce and being on the same team as humans proved to be an advantage. Friendlier wolves were much more likely to be tolerated and accepted by humans as pets. I guess if you think about it, dogs kind of domesticated themselves.

What's interesting is that as this group of wolves became more docile over time, their physical appearances began to change as well. They got upright wagging tails, and floppy ears, and spotted coats. They actually become distinct enough from wolves Canis lupus, that we now classify them as their own subspecies, Canis lupus familiaris. 

Fast forward to present day and you can see that we went really super crazy with this whole selective breeding thing. Especially within the last few hundred years or so, we've breed dogs for very specific cognitive aesthetic traits, results in dogs as big as ponies and small enough to fit inside of Paris Hilton's purse.

This is kind of interesting. It's a portrait of a man and his pug from 1745. And here's one of an angry woman and her pug from 255 years later. And finally this is what pugs look like today.

So we have this thing called a cranial index which we use to categorize animals. It's a ratio of the skull's maximum width to its maximum length. An example of a dog breed with a low cranial index is a gray hound with their long snout and their low forehead. A pug, on the other hand, has a high cranial index. Animals with high cranial indexes are called brachycephalic and have high foreheads, shortened snouts, and enlarged eyes. With certain dog breeds we've ended up heavily exaggerating these features, either consciously or not, ending up with dogs that look suspiciously human-like.

And while they might look super adorbs(short for adorable), animals with high cranial indexes are subject to a multitude of heath problems. They have a difficult time regulating their body temperature because their smaller mouths mean less surface area for water to evaporate resulting in less effective panting. Their exaggerated ocular orbitals put them at risk for their eyes literally popping right out of their heads should they accidentally sustain any trauma to the back of the skull. And because their skulls have been so dramatically shortened, it's results in a bunch of skin bunching up on their faces which can get really dirty and nasty and result in bacterial infections and all kinds of pretty gross stuff. All because we wanted to have a wolf that looked like this.

It kind of makes you think about the depth of impact that we humans have when we go around messing with nature.

Thanks for watching. This has been an episode of Brain Scoop. This has been a Brain Scoop T-shirt, and I'll see you next time.