The Evolution of Speech

Transcription

1 The Evolution of Speech Q: How did speech arise in humans? A: We don t know. 1

2 How did speech arise in humans? scholars: interminable, acrimonious debates limited scientific data 1860: Paris Linguistic Society banned discussion of the topic (not worthy of consideration) How did speech arise in humans? Speculative Accounts: Proposed Origin of Speech based on onomatopoeia: animal and environmental sounds arose from human sounds indicating pleasure, discomfort (laughs, groans) arosefrom music arose from sign arose from primate vocalizations (like vervet calls) did not arise from anything else (no basis in human or other animal behaviour) 2

3 Are we (homo sapiens) the only creatures ever to have used speech? We don t know. No other extant primates use speech. However, it is possible that some close but nowextinct relatives, such as Neanderthals, did speak. How do we explain the use of speech by humans but not by other extant primates? 1. Vocal anatomy itself: position of the larynx (hyoid bone in particular) in humans vs. other primates 2. Brain development: vocal mimetic abilities in humans vs. other primates 3

4 NON-HUMAN ANIMALS Other animals make sounds for Defense Mating Other social purposes (bonding, sharing) However, the mechanisms they use are not necessarily the same as ours... Bird vocal structures illustrate parallel evolution avian sound-producing mechanism evolved separately from that of humans. little connection with our speech production mechanism 4

5 Avian Vocal Anatomy syrinx syringeal consists of membranes that vibrate Source: birdwatching-bliss.com Avian Vocal Anatomy sits at the junction of the bronchi some birds can produce sound on one side only OR two distinct sounds simultaneously 5

6 Photograph of the ventral surface of the syrinx of a male wild-type domestic fowl. Krakauer A H et al. J Exp Biol 2009;212: a: tracheal rings; b: tracheal narrowing; c: syrinx 2009 by The Company of Biologists Ltd 6

7 Dolphins: don t have vocal folds produce vocalizations through vibrating tissues in nasal passageways ( phonic lips ) Produce sound at audible frequencies for social purposes and at much higher frequencies for echolocation Dolphin Sound Source: Dolphin Larynx: no true vocal folds

8 Dolphin Larynx: no true vocal folds ( 8

9 Evolutionary advantages of sound production defense, food sharing, mating Not surprising that sound-producing capabilities are seen more than once in evolutionary history. tolweb.org 9

10 Placental Mammals 10

11 Primates Source: Tree of Life web project Catarrhini Source: Tree of Life web project 11

12 Hominids (Hominidae) Source: Tree of Life web project Hominid Group all modern and extinct Great Apes (modern humans, chimpanzees, gorillas and orangutans) PLUS all their immediate ancestors). Subgroup: Hominin Group modern humans, extinct human species and all our immediate ancestors (including members of the genera Homo, Australopithecus, Paranthropus and Ardipithecus). source: Australian Museum 12

13 Hominids (Hominidae) Genome sequencing shows 98.8% similarity between modern humans and chimps/bonobos. This branch-off occurred about 5 7 million years ago Smithsonian: 13

14 ARDI Hypothetical reconstruction of ardipithecus ramidus (ca. 4.4 million years ago) Source: bbc.co.uk Lucy Hypothetical reconstruction of Lucy ca. 3 million yrs ago (Australopithecus) Source: bbc.co.uk 14

15 Homo sapiens erectus ergaster rudolfensis habilis wise upright working found near L. Rudolf able Source: Tree of Life web project Also homo neanderthalensis (disc. 1829) homo floresiensis (disc. 2003) homo naledi (first reported 2015) Source: Tree of Life web project 15

16 How homo neanderthalensis might have looked. Source: BBC Homo Neanderthanesis our closest extinct relatives lived 200,000 to 40,000 years ago and therefore coexisted with homo sapiens 16

17 Homo Neanderthanesis Physical Large nose, angled cheek bones Bodies: short and stocky compared to us Brains: same size as ours or larger Behavioral/social used tools for hunting, sewing; used fire built shelters, wore clothing probably buried their dead, sometimes in marked graves 17

18 Homo Neanderthanesis ALSO: Genome sequencing (2010) shows 99.7% similarity between neanderthals and homo sapiens è Neanderthals interbred with homo sapiens after migration from Africa. All people of non-african origin are part neanderthal. Depiction of homo floresiensis (Hobbit) Source: discovermagazine.com 18

19 How homo neanderthalensis might have looked. How homo floresiensis might have looked Source: Wikimedia Commons Source: janesoceania.com 19

20 Two critical areas of change as we diverged from our evolutionary relatives: 1. Changes to peripheral mechanisms 2. Changes to central neural mechanisms There are no specialized organs of speech. Tongue, lips, nose, teeth evolved to serve other functions: e.g., mastication, deglutition, gustation. 20

21 There are no specialized organs of speech. Tongue, lips, nose, teeth evolved to serve other functions Many other animals have these structures + larynx, vocal folds, but don t speak èthese structures can be used to produce speech Exaptation: using something for a purpose other than its original function Two critical areas of change as we diverged from our evolutionary relatives: 1. Changes to peripheral mechanisms 2. Changes to central neural mechanisms 21