Speaker 1: Welcome to brain Stuff production of I Heart Radio, Hey
Speaker 1: brain Stuff, Lauren vog obam here. Back in the nineteen
Speaker 1: sixties and seventies, it was all the rage with primatologists
Speaker 1: to conduct studies in which infant chimpanzees were raised as
Speaker 1: though they were human infants. This practice tested the limits
Speaker 1: of what a non human primate could accomplish if raised
Speaker 1: in human society, aiming to parse what was nature and
Speaker 1: what was nurture. These studies often played out like dark
Speaker 1: fairy tales, with chimp babies growing up into tragic half humans,
Speaker 1: living between two worlds and belonging to neither. But one
Speaker 1: thing that came out of these studies was the realization
Speaker 1: that although these chimpanzees raised in human environments learned how
Speaker 1: to behave in eerily human ish ways, none of them
Speaker 1: could ever be taught to talk. We spoke with Asif Zanfar,
Speaker 1: a professor of psychology at the Princeton Neuroscience Institute. He said,
Speaker 1: I think that surprised a lot of people. They weren't
Speaker 1: even producing rudimentary words a drunk person would say. According
Speaker 1: to Susan Far, that led researchers to develop a few
Speaker 1: theories about why this could be one that other primates
Speaker 1: might have the brains to produce speech, after all, they
Speaker 1: can do rudimentary symbolic communication, but they're lacking the vocal
Speaker 1: anatomy to make speech sounds. Two that primates completely lack
Speaker 1: the neural control to produce speech sounds, or three that
Speaker 1: they lack both the proper brain and the proper anatomy
Speaker 1: for speech. Around this time, linguist and cognitive scientist Philip
Speaker 1: Lieberman tried to determine which, if any, of these conclusions
Speaker 1: were true. In a nineteen sixty nine study, Lieberman and
Speaker 1: his co authors examined cadavers of Reesis monkeys to estimate,
Speaker 1: based on their anatomy, what speech sounds they could theoretically
Speaker 1: be able to make. A Lieberman's conclusion was that, based
Speaker 1: on the anatomy of a reesis, they wouldn't be able
Speaker 1: to speak even if their brains were wired just like ours.
Speaker 1: Based on this study, the idea took hold that one
Speaker 1: of the main reasons chimps and other primates can't speak
Speaker 1: is that they lack the vocal anatomy to do so.
Speaker 1: But now half century later, a study published in Science
Speaker 1: Advances has revisited the question of why monkeys can't talk,
Speaker 1: and it debunks Lieberman's notion that monkeys lack the appropriate
Speaker 1: vocal anatomy. Instead, they say, monkeys mouths and throats could
Speaker 1: form human sounding words, but their brains aren't good enough
Speaker 1: to tell their body how to do so. Sasan Far
Speaker 1: and an international team of researchers captured X ray video
Speaker 1: of a resis eating, squawking, and making facial expressions, then
Speaker 1: made a model of those movements that could predict the
Speaker 1: potential vocal range of the animal. They found that anatomically speaking,
Speaker 1: a resis has everything it needs to form entire sentences
Speaker 1: of human speech, although its voice definitely wouldn't sound human.
Speaker 1: What it doesn't have is the necessary neural ability to
Speaker 1: coordinate respiration, oral facial muscle control, and laryngeal tension, all
Speaker 1: things we have to do in order to talk. In fact,
Speaker 1: sizan Far says, all of the old World primates, all
Speaker 1: the species in Africa and Asia, including the great apes,
Speaker 1: probably have the same ability. They conclude this because these
Speaker 1: monkeys and apes in large part have very similar vocal
Speaker 1: and facial expressions. Why humans got such a tricked out
Speaker 1: brain in comparison to our primate relatives is hard to know,
Speaker 1: but it's fun to think about. Sison Far said, nobody's
Speaker 1: sure what driving forces and pressures lead to humans elaborating
Speaker 1: a more sophisticated control of the vocal anatomy. Maybe as
Speaker 1: group size increased, it became inefficient to communicate via physical grooming,
Speaker 1: and you had to maintain relationships with many individuals, so
Speaker 1: the burden to maintain those relationships was shifted to the
Speaker 1: vocal acoustic domain. But to address what we all really
Speaker 1: want to know here, how feasible is a Planet of
Speaker 1: the Apes scenario? Sison Far said, Well, I don't know,
Speaker 1: but the new version of Planet of the Apes got
Speaker 1: it right. In the first movie of the new series
Speaker 1: is the chimpanzee was given a drug to enhance its cognition,
Speaker 1: giving it the ability to speak. They didn't even address
Speaker 1: vocal anatomies, so they accidentally got it right. Hollywood is
Speaker 1: president sometimes. One theory about why humans have more communicative
Speaker 1: and vocal learning capabilities than other primates is that a
Speaker 1: lot of our brain development happens out in the world
Speaker 1: rather than in utero. According to Zampar, the brain of
Speaker 1: a human infant is only developed at birth, while that
Speaker 1: of a Reese's Monkey is about six developed at birth.
Speaker 1: Today's episode was written by Jesslyn Shields and produced by
Speaker 1: Tyler Clang. Brain Stuff is a production of I Heart
Speaker 1: Radio's How Stuff Works. For more in this and lots
Speaker 1: of other brainy topics, visit our home planet, how stuff
Speaker 1: works dot com and for more podcasts from my heart
Speaker 1: radio is the heart radio app, Apple Podcasts, or wherever
Speaker 1: you listen to your favorite shows.