WEBVTT - Do Monkeys Lack the Brains or the Vocal Anatomy for Human Speech? 0:00:01.920 --> 0:00:06.560 Welcome to brain Stuff production of I Heart Radio, Hey 0:00:06.600 --> 0:00:10.160 brain Stuff, Lauren vog obam here. Back in the nineteen 0:00:10.200 --> 0:00:13.280 sixties and seventies, it was all the rage with primatologists 0:00:13.280 --> 0:00:16.560 to conduct studies in which infant chimpanzees were raised as 0:00:16.560 --> 0:00:20.040 though they were human infants. This practice tested the limits 0:00:20.040 --> 0:00:22.640 of what a non human primate could accomplish if raised 0:00:22.640 --> 0:00:26.120 in human society, aiming to parse what was nature and 0:00:26.160 --> 0:00:29.600 what was nurture. These studies often played out like dark 0:00:29.640 --> 0:00:33.479 fairy tales, with chimp babies growing up into tragic half humans, 0:00:33.520 --> 0:00:37.279 living between two worlds and belonging to neither. But one 0:00:37.320 --> 0:00:39.640 thing that came out of these studies was the realization 0:00:39.720 --> 0:00:43.239 that although these chimpanzees raised in human environments learned how 0:00:43.240 --> 0:00:46.080 to behave in eerily human ish ways, none of them 0:00:46.120 --> 0:00:51.000 could ever be taught to talk. We spoke with Asif Zanfar, 0:00:51.320 --> 0:00:55.280 a professor of psychology at the Princeton Neuroscience Institute. He said, 0:00:55.640 --> 0:00:58.160 I think that surprised a lot of people. They weren't 0:00:58.200 --> 0:01:02.920 even producing rudimentary words a drunk person would say. According 0:01:02.920 --> 0:01:05.920 to Susan Far, that led researchers to develop a few 0:01:05.959 --> 0:01:09.720 theories about why this could be one that other primates 0:01:09.800 --> 0:01:12.640 might have the brains to produce speech, after all, they 0:01:12.640 --> 0:01:16.720 can do rudimentary symbolic communication, but they're lacking the vocal 0:01:16.720 --> 0:01:21.600 anatomy to make speech sounds. Two that primates completely lack 0:01:21.680 --> 0:01:25.399 the neural control to produce speech sounds, or three that 0:01:25.480 --> 0:01:28.640 they lack both the proper brain and the proper anatomy 0:01:28.920 --> 0:01:33.880 for speech. Around this time, linguist and cognitive scientist Philip 0:01:33.920 --> 0:01:37.560 Lieberman tried to determine which, if any, of these conclusions 0:01:37.600 --> 0:01:41.480 were true. In a nineteen sixty nine study, Lieberman and 0:01:41.480 --> 0:01:44.800 his co authors examined cadavers of Reesis monkeys to estimate, 0:01:44.920 --> 0:01:48.280 based on their anatomy, what speech sounds they could theoretically 0:01:48.360 --> 0:01:51.800 be able to make. A Lieberman's conclusion was that, based 0:01:51.840 --> 0:01:54.559 on the anatomy of a reesis, they wouldn't be able 0:01:54.640 --> 0:01:57.559 to speak even if their brains were wired just like ours. 0:01:58.280 --> 0:02:00.840 Based on this study, the idea took hold that one 0:02:00.880 --> 0:02:03.800 of the main reasons chimps and other primates can't speak 0:02:04.120 --> 0:02:06.160 is that they lack the vocal anatomy to do so. 0:02:06.840 --> 0:02:09.919 But now half century later, a study published in Science 0:02:09.919 --> 0:02:13.160 Advances has revisited the question of why monkeys can't talk, 0:02:13.560 --> 0:02:16.480 and it debunks Lieberman's notion that monkeys lack the appropriate 0:02:16.560 --> 0:02:21.120 vocal anatomy. Instead, they say, monkeys mouths and throats could 0:02:21.160 --> 0:02:24.639 form human sounding words, but their brains aren't good enough 0:02:24.680 --> 0:02:28.240 to tell their body how to do so. Sasan Far 0:02:28.360 --> 0:02:31.320 and an international team of researchers captured X ray video 0:02:31.360 --> 0:02:35.119 of a resis eating, squawking, and making facial expressions, then 0:02:35.280 --> 0:02:37.560 made a model of those movements that could predict the 0:02:37.560 --> 0:02:42.400 potential vocal range of the animal. They found that anatomically speaking, 0:02:42.639 --> 0:02:45.720 a resis has everything it needs to form entire sentences 0:02:45.760 --> 0:02:49.160 of human speech, although its voice definitely wouldn't sound human. 0:02:50.040 --> 0:02:52.760 What it doesn't have is the necessary neural ability to 0:02:52.840 --> 0:02:58.040 coordinate respiration, oral facial muscle control, and laryngeal tension, all 0:02:58.120 --> 0:03:01.640 things we have to do in order to talk. In fact, 0:03:01.680 --> 0:03:04.760 sizan Far says, all of the old World primates, all 0:03:04.760 --> 0:03:07.720 the species in Africa and Asia, including the great apes, 0:03:08.160 --> 0:03:11.519 probably have the same ability. They conclude this because these 0:03:11.560 --> 0:03:15.040 monkeys and apes in large part have very similar vocal 0:03:15.080 --> 0:03:19.799 and facial expressions. Why humans got such a tricked out 0:03:19.800 --> 0:03:22.720 brain in comparison to our primate relatives is hard to know, 0:03:23.120 --> 0:03:26.919 but it's fun to think about. Sison Far said, nobody's 0:03:26.960 --> 0:03:30.360 sure what driving forces and pressures lead to humans elaborating 0:03:30.440 --> 0:03:34.040 a more sophisticated control of the vocal anatomy. Maybe as 0:03:34.080 --> 0:03:37.760 group size increased, it became inefficient to communicate via physical grooming, 0:03:38.000 --> 0:03:41.120 and you had to maintain relationships with many individuals, so 0:03:41.200 --> 0:03:43.840 the burden to maintain those relationships was shifted to the 0:03:43.880 --> 0:03:48.680 vocal acoustic domain. But to address what we all really 0:03:48.680 --> 0:03:51.440 want to know here, how feasible is a Planet of 0:03:51.440 --> 0:03:55.560 the Apes scenario? Sison Far said, Well, I don't know, 0:03:55.680 --> 0:03:57.680 but the new version of Planet of the Apes got 0:03:57.680 --> 0:04:00.000 it right. In the first movie of the new series 0:04:00.120 --> 0:04:02.960 is the chimpanzee was given a drug to enhance its cognition, 0:04:03.200 --> 0:04:06.200 giving it the ability to speak. They didn't even address 0:04:06.280 --> 0:04:09.600 vocal anatomies, so they accidentally got it right. Hollywood is 0:04:09.600 --> 0:04:14.960 president sometimes. One theory about why humans have more communicative 0:04:15.000 --> 0:04:18.120 and vocal learning capabilities than other primates is that a 0:04:18.160 --> 0:04:20.320 lot of our brain development happens out in the world 0:04:20.480 --> 0:04:24.240 rather than in utero. According to Zampar, the brain of 0:04:24.240 --> 0:04:27.839 a human infant is only developed at birth, while that 0:04:27.960 --> 0:04:30.880 of a Reese's Monkey is about six developed at birth. 0:04:36.120 --> 0:04:38.520 Today's episode was written by Jesslyn Shields and produced by 0:04:38.520 --> 0:04:40.960 Tyler Clang. Brain Stuff is a production of I Heart 0:04:41.000 --> 0:04:43.159 Radio's How Stuff Works. For more in this and lots 0:04:43.160 --> 0:04:45.679 of other brainy topics, visit our home planet, how stuff 0:04:45.680 --> 0:04:48.320 works dot com and for more podcasts from my heart 0:04:48.400 --> 0:04:51.440 radio is the heart radio app, Apple Podcasts, or wherever 0:04:51.480 --> 0:04:52.719 you listen to your favorite shows.