1 00:00:01,920 --> 00:00:06,560 Speaker 1: Welcome to brain Stuff production of I Heart Radio, Hey 2 00:00:06,600 --> 00:00:10,160 Speaker 1: brain Stuff, Lauren vog obam here. Back in the nineteen 3 00:00:10,200 --> 00:00:13,280 Speaker 1: sixties and seventies, it was all the rage with primatologists 4 00:00:13,280 --> 00:00:16,560 Speaker 1: to conduct studies in which infant chimpanzees were raised as 5 00:00:16,560 --> 00:00:20,040 Speaker 1: though they were human infants. This practice tested the limits 6 00:00:20,040 --> 00:00:22,640 Speaker 1: of what a non human primate could accomplish if raised 7 00:00:22,640 --> 00:00:26,120 Speaker 1: in human society, aiming to parse what was nature and 8 00:00:26,160 --> 00:00:29,600 Speaker 1: what was nurture. These studies often played out like dark 9 00:00:29,640 --> 00:00:33,479 Speaker 1: fairy tales, with chimp babies growing up into tragic half humans, 10 00:00:33,520 --> 00:00:37,279 Speaker 1: living between two worlds and belonging to neither. But one 11 00:00:37,320 --> 00:00:39,640 Speaker 1: thing that came out of these studies was the realization 12 00:00:39,720 --> 00:00:43,239 Speaker 1: that although these chimpanzees raised in human environments learned how 13 00:00:43,240 --> 00:00:46,080 Speaker 1: to behave in eerily human ish ways, none of them 14 00:00:46,120 --> 00:00:51,000 Speaker 1: could ever be taught to talk. We spoke with Asif Zanfar, 15 00:00:51,320 --> 00:00:55,280 Speaker 1: a professor of psychology at the Princeton Neuroscience Institute. He said, 16 00:00:55,640 --> 00:00:58,160 Speaker 1: I think that surprised a lot of people. They weren't 17 00:00:58,200 --> 00:01:02,920 Speaker 1: even producing rudimentary words a drunk person would say. According 18 00:01:02,920 --> 00:01:05,920 Speaker 1: to Susan Far, that led researchers to develop a few 19 00:01:05,959 --> 00:01:09,720 Speaker 1: theories about why this could be one that other primates 20 00:01:09,800 --> 00:01:12,640 Speaker 1: might have the brains to produce speech, after all, they 21 00:01:12,640 --> 00:01:16,720 Speaker 1: can do rudimentary symbolic communication, but they're lacking the vocal 22 00:01:16,720 --> 00:01:21,600 Speaker 1: anatomy to make speech sounds. Two that primates completely lack 23 00:01:21,680 --> 00:01:25,399 Speaker 1: the neural control to produce speech sounds, or three that 24 00:01:25,480 --> 00:01:28,640 Speaker 1: they lack both the proper brain and the proper anatomy 25 00:01:28,920 --> 00:01:33,880 Speaker 1: for speech. Around this time, linguist and cognitive scientist Philip 26 00:01:33,920 --> 00:01:37,560 Speaker 1: Lieberman tried to determine which, if any, of these conclusions 27 00:01:37,600 --> 00:01:41,480 Speaker 1: were true. In a nineteen sixty nine study, Lieberman and 28 00:01:41,480 --> 00:01:44,800 Speaker 1: his co authors examined cadavers of Reesis monkeys to estimate, 29 00:01:44,920 --> 00:01:48,280 Speaker 1: based on their anatomy, what speech sounds they could theoretically 30 00:01:48,360 --> 00:01:51,800 Speaker 1: be able to make. A Lieberman's conclusion was that, based 31 00:01:51,840 --> 00:01:54,559 Speaker 1: on the anatomy of a reesis, they wouldn't be able 32 00:01:54,640 --> 00:01:57,559 Speaker 1: to speak even if their brains were wired just like ours. 33 00:01:58,280 --> 00:02:00,840 Speaker 1: Based on this study, the idea took hold that one 34 00:02:00,880 --> 00:02:03,800 Speaker 1: of the main reasons chimps and other primates can't speak 35 00:02:04,120 --> 00:02:06,160 Speaker 1: is that they lack the vocal anatomy to do so. 36 00:02:06,840 --> 00:02:09,919 Speaker 1: But now half century later, a study published in Science 37 00:02:09,919 --> 00:02:13,160 Speaker 1: Advances has revisited the question of why monkeys can't talk, 38 00:02:13,560 --> 00:02:16,480 Speaker 1: and it debunks Lieberman's notion that monkeys lack the appropriate 39 00:02:16,560 --> 00:02:21,120 Speaker 1: vocal anatomy. Instead, they say, monkeys mouths and throats could 40 00:02:21,160 --> 00:02:24,639 Speaker 1: form human sounding words, but their brains aren't good enough 41 00:02:24,680 --> 00:02:28,240 Speaker 1: to tell their body how to do so. Sasan Far 42 00:02:28,360 --> 00:02:31,320 Speaker 1: and an international team of researchers captured X ray video 43 00:02:31,360 --> 00:02:35,119 Speaker 1: of a resis eating, squawking, and making facial expressions, then 44 00:02:35,280 --> 00:02:37,560 Speaker 1: made a model of those movements that could predict the 45 00:02:37,560 --> 00:02:42,400 Speaker 1: potential vocal range of the animal. They found that anatomically speaking, 46 00:02:42,639 --> 00:02:45,720 Speaker 1: a resis has everything it needs to form entire sentences 47 00:02:45,760 --> 00:02:49,160 Speaker 1: of human speech, although its voice definitely wouldn't sound human. 48 00:02:50,040 --> 00:02:52,760 Speaker 1: What it doesn't have is the necessary neural ability to 49 00:02:52,840 --> 00:02:58,040 Speaker 1: coordinate respiration, oral facial muscle control, and laryngeal tension, all 50 00:02:58,120 --> 00:03:01,640 Speaker 1: things we have to do in order to talk. In fact, 51 00:03:01,680 --> 00:03:04,760 Speaker 1: sizan Far says, all of the old World primates, all 52 00:03:04,760 --> 00:03:07,720 Speaker 1: the species in Africa and Asia, including the great apes, 53 00:03:08,160 --> 00:03:11,519 Speaker 1: probably have the same ability. They conclude this because these 54 00:03:11,560 --> 00:03:15,040 Speaker 1: monkeys and apes in large part have very similar vocal 55 00:03:15,080 --> 00:03:19,799 Speaker 1: and facial expressions. Why humans got such a tricked out 56 00:03:19,800 --> 00:03:22,720 Speaker 1: brain in comparison to our primate relatives is hard to know, 57 00:03:23,120 --> 00:03:26,919 Speaker 1: but it's fun to think about. Sison Far said, nobody's 58 00:03:26,960 --> 00:03:30,360 Speaker 1: sure what driving forces and pressures lead to humans elaborating 59 00:03:30,440 --> 00:03:34,040 Speaker 1: a more sophisticated control of the vocal anatomy. Maybe as 60 00:03:34,080 --> 00:03:37,760 Speaker 1: group size increased, it became inefficient to communicate via physical grooming, 61 00:03:38,000 --> 00:03:41,120 Speaker 1: and you had to maintain relationships with many individuals, so 62 00:03:41,200 --> 00:03:43,840 Speaker 1: the burden to maintain those relationships was shifted to the 63 00:03:43,880 --> 00:03:48,680 Speaker 1: vocal acoustic domain. But to address what we all really 64 00:03:48,680 --> 00:03:51,440 Speaker 1: want to know here, how feasible is a Planet of 65 00:03:51,440 --> 00:03:55,560 Speaker 1: the Apes scenario? Sison Far said, Well, I don't know, 66 00:03:55,680 --> 00:03:57,680 Speaker 1: but the new version of Planet of the Apes got 67 00:03:57,680 --> 00:04:00,000 Speaker 1: it right. In the first movie of the new series 68 00:04:00,120 --> 00:04:02,960 Speaker 1: is the chimpanzee was given a drug to enhance its cognition, 69 00:04:03,200 --> 00:04:06,200 Speaker 1: giving it the ability to speak. They didn't even address 70 00:04:06,280 --> 00:04:09,600 Speaker 1: vocal anatomies, so they accidentally got it right. Hollywood is 71 00:04:09,600 --> 00:04:14,960 Speaker 1: president sometimes. One theory about why humans have more communicative 72 00:04:15,000 --> 00:04:18,120 Speaker 1: and vocal learning capabilities than other primates is that a 73 00:04:18,160 --> 00:04:20,320 Speaker 1: lot of our brain development happens out in the world 74 00:04:20,480 --> 00:04:24,240 Speaker 1: rather than in utero. According to Zampar, the brain of 75 00:04:24,240 --> 00:04:27,839 Speaker 1: a human infant is only developed at birth, while that 76 00:04:27,960 --> 00:04:30,880 Speaker 1: of a Reese's Monkey is about six developed at birth. 77 00:04:36,120 --> 00:04:38,520 Speaker 1: Today's episode was written by Jesslyn Shields and produced by 78 00:04:38,520 --> 00:04:40,960 Speaker 1: Tyler Clang. Brain Stuff is a production of I Heart 79 00:04:41,000 --> 00:04:43,159 Speaker 1: Radio's How Stuff Works. For more in this and lots 80 00:04:43,160 --> 00:04:45,679 Speaker 1: of other brainy topics, visit our home planet, how stuff 81 00:04:45,680 --> 00:04:48,320 Speaker 1: works dot com and for more podcasts from my heart 82 00:04:48,400 --> 00:04:51,440 Speaker 1: radio is the heart radio app, Apple Podcasts, or wherever 83 00:04:51,480 --> 00:04:52,719 Speaker 1: you listen to your favorite shows.