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Hey guys, Joe here.
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So I'm a dad now.
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And my wife got me these socks.
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They're covered in my son's face.
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Pretty much the cutest socks ever.
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Now that I'm a dad, I realize I'm basically only going to watch animated movies for the next decade.
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And as I started thinking back about all the great Disney movies through the years, I noticed something weird has been happening to the princesses.
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In the earliest Disney films, the princesses more or less look like real, human women.
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But through the years, something strange happens.
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Heads get bigger compared to their bodies, and their eyes get bigger compared to their heads.
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By the time we get to Elsa, it's clear this 22-year old Frozen princess doesn't look like an adult female.
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She has the body ratios of an 8 year old.
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Moana is supposedly 16 years old, but she has the body ratios of a 4 year old.
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Disney princesses have been looking more and more like children.
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And this case of the Benjamin Buttons isn't just happening to princesses.
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In fact, this is true all over Toon-Town.
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The designs of almost all cartoon characters have changed over time, and almost always in the same way.
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As they get older, they age in reverse.
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As we develop, we get a literal "head start." Our arms, legs, and bodies catch up as we get older.
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That's why a newborn's eyes are already 75% of their adult diameter, and our brains hit 55% of their adult volume by 3 months of age.
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Small bodies, big heads, big eyes.
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Biologist Konrad Lorenz speculated that these babyish features trigger an instinct in adult mammals to give love and attention.
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When I show you this photo of a kitten, something happens in your brain that makes you want to cuddle and feed it--unless you're some kind of unfeeling monster.
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In other words, "cuteness" is nature's secret weapon to persuade adults into caring for babies.
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Disney is just using the same biological trick to encourage audiences to root for their characters.
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That's why cartoon protagonists tend to have juvenile characteristics, and the villains… not so much.
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But this doesn't just happen in Fantasyland.
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Which would you rather cuddle?
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This cavalier king charles spaniel?
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Or this wolf?
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This floppy-eared ball of snuggles has been selectively bred to be cute.
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It retains juvenile features into adulthood, or, what biologists call neoteny.
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We see neoteny in many domesticated animals.
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Although selecting for cuteness can explain the spaniel, animals like pigs show neoteny too.
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Why would ancient humans care about the cuddle-ability of something they were raising for bacon?
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Well, maybe cuteness is just a side-effect?
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The most important trait in becoming a domesticated animal is… tameness.
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Whether it's a companion, a worker, or a food source, you can't have a productive relationship with fearful or aggressive animals.
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That fight or flight response is something that most animals only acquire as they get older--baby animals are pretty chill with humans.
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So an animal that somehow never "grows up" in that sense might make the best candidate for domestication.
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Beginning in the 1950s, Soviet scientist Dmitry Belyaev began a breeding experiment to study this idea, using wild silver foxes.
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The foxes were tested for their reaction to human contact, and only the foxes that were friendly toward experimenters were allowed to breed.
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After just 20 generations, his foxes had not only changed in behavior, but also in appearance.
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Floppy ears, smaller jaws, and shorter tails that now wagged whenever humans were around.
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Belyaev noted changes in hormones and brain chemistry that he suspected were capable of reshaping the foxes' external features.
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What does this tell us?
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If you select for one childish trait, a bunch of others tend to come along with it.
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Evolutionary biologist Stephen J. Gould noticed that the same was true of the world's most famous cartoon character: Mickey Mouse.
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OG Mickey was... kind of a jerk.
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But as his personality got softer and sweeter, so did his appearance.
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By the 1950s, Mickey had not only become the child-like mouse we know today, he'd become a nice guy.
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But beyond pets or cartoons, you can also see neoteny in yourself.
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Most biologists agree that humans are, in many ways, big babies.
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Compared to other adult primates, we grow less body hair, have shorter limbs, and flatter faces.
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And if you compare how much a chimp's skull morphs as it matures, you can see that our skull shape changes much less.
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Our neoteny offered us lots of evolutionary advantages.
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Less body hair meant we could run farther in that African heat, and our faces were more visible to each other as social interaction became more important.
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Also, suppressing our own fight or flight response meant we could cooperate and organize in larger numbers.
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And most importantly, these big brains need a lot of room and time to develop, which is why we rely on our parents for much longer than most mammals.
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It might not be a coincidence that the more complex our society gets, the more time humans need to become independent.
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Childhood is a time for experimentation and learning--most animals get locked into pretty rigid programs by the time they're adults.
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By extending our childhood into adulthood, we can learn and change as long as we live.
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Maybe that's why so many of us still love cartoons.
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Because we may get old, but we never grow up. That's what makes us human.
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Stay curious.