Constraining the time when language evolved

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Constraining the time when language evolved

• Sverker Johansson
• School of Education Communication
• University of Jönköping, Sweden

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Precise time of language emergence cannot be
determined
But
Upper and lower limits can be set
Time limits add constraints to theorizing about
language origins
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Upper limits

• Trivial limit
• The other apes do not have language
• Most parsimonious conclusion
• Our common ancestor did not have language.
• Upper age limit
• At the time of the common ancestor.
• Common ancestor most likely lived 5-8 million
  years ago
• Upper age limit in the vicinity of 5 million
  years

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Upper limits II

• Non-trivial limits possible?
• Minimum brain size needed for language?
• Possibly but given what chimps can be taught,
  the limit cannot be much beyond chimp capacity.
  No way to determine a firm limit absent living
  australopiths. Hobbits?
• Language associated with symbolic culture?
• Does absence of culture imply absence of
  language? Possibly...
• Does absence of durable material artefacts imply
  absence of language? Hardly!
• Speech anatomy needed for language?
• Not if sign language came first.
• Non-trivial upper limit not possible!

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Lower limits

• Trivial limit or is it?
• All modern humans have language
• Most parsimonious conclusion
• Our last common ancestor had language.
• Lower age limit
• At the time of the common ancestor.
• Common ancestor most likely lived 100,000-200,000
  years ago
• Genetic data mitochondrial Eve, Y-Adam etc.
• Archeological data indicating when we left Africa
  and arrived elsewhere
• Lower age limit in the vicinity of 100,000 years
• Not trivial theories placing language origins
  at less than 100,000 years are far from rare.

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Lower limits II

• Language fossils?
• Language as such not visible in fossils, but
• Anatomical language adaptations might be.
• Traces of other symbolic behavior might be.
• Two kinds of limits possible
• Directly from the age of such finds.
• Indirectly if anatomy or symbols found in
  different branches of the family tree, the limit
  is pushed back to their common ancestor.

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Lower limits III -- Anatomy

• Speech organs
• Hearing organs
• Brain
• Neural connections

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Anatomy I Speech organs

• Speech organs
• Human vocal tract likely speech adaptation (but
  see also presentation by Fitch here)
• Vocal tract shape affects skull base and hyoid
  bone.
• Skull base near-modern shape in Homo erectus but
  affected by brain and face reshaping as well
  not reliable as speech indicator.
• Hyoid bone more useful, but rare as fossil.
  Neanderthal hyoid near-modern shape.

Neanderthal hyoid
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Anatomy II Hearing organs

• Human ears tuned for 3-5 kHz sensitivity compared
  with chimps. Adaptation for speech perception?
  (but see also Zuidema ODonnell here)
• Human-shaped middle ear in 400,000-year old
  fossils (Sima de los Huesos, Spain). Likely
  Neanderthal ancestors.
• Genetic traces of strong natural selection in
  middle-ear structural genes.

Human (blue)
Martínez et al (2004) PNAS 101(27)9976
H heidelbergensis (red, purple)
Chimp (green)
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Anatomy III Brain

• Gross anatomy of brain visible in fossils.
• The age of e.g. Brocas area might be determined.
• Ditto lateralization.
• BUT
• Structures similar in gross anatomy to Broca,
  Wernicke etc. found in other apes.
• Ditto lateralization.
• No useful age limit from gross brain structure.

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Anatomy IV Nerves

• Neural canals in bone may indicate thickness of
  nerve.
• Thicker nerve ? improved sensitivity and control.
• Improved control of vocal organs may be speech
  adaptation.
• Possible candidates
• Hypoglossal canal (to the tongue)
• Contradictory interpretations of fossil evidence
  no firm conclusion possible.
• Nerves to the thorax (breathing control?)
• Wide canals in us and Neanderthals, narrow in
  apes and in Homo ergaster.

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Anatomy conclusions

• Several hints of speech adaptations found in
  Neanderthal lineage.
• No individual anatomical indication is strongly
  compelling, but their joint weight is
  substantial.
• This implies the last common ancestor of us and
  Neanderthals likely had some form of speech.

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Lower limits III -- Symbolics

• Art and ornaments imply symbolic capacity?
• Advanced creative tool making?
• Cognitive Big Bang 40,000 years ago?

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Symbols I Big Bang?

• Homo sapiens turns up suddenly in Europe 40,000
  years ago, with advanced tools and art.
• BUT
• Europe is not the whole world.
• We have a long history in Africa, gradually
  developing the advanced package (McBrearty
  Brooks 2000).

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Symbols II Pre-40k culture
Used pigment chunk, gt200,000 years BP
Beads (ostrich eggs), 52,000 BP
McBrearty Brooks (2000)
Barbed bone tools, Katanda, 90,000 years BP
Barham (2002) Curr Anthro 44627
Engraved ochre, 77,000 years BP
dErrico et al
Yellen et al (1995) Science 268553
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Symbols III Pre-sapiens art?
Figurine or just funny rock?

• No uncontested objects of art from other species
  of Homo.
• Possible art goes back to Acheulean period.
• Fair amount of evidence of simple symbolic
  behavior among Neanderthals (art, pigment use,
  burials), though it remains contested.

Neanderthal ornaments? 33,000 BP dErrico et al
(2003) JWP 171
Bednarik (2003) Curr Anthro 44405
Yellen et al (1995) Science 268553
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Symbol conclusions

• No 40,000 BP revolution.
• Gradual emergence of clearer and clearer
  indications of symbolic behavior across several
  hundred thousand years.
• Likely symbolic capacity among Neanderthals.
• Possible symbolic capacity among earlier people.
• Conclusions
• Symbolic capacity much older than 40,000 years
• Fair support for symbolic capacity in
  Neanderthals, and thus in our common ancestor.
• Good match with the anatomical evidence.

Yellen et al (1995) Science 268553
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Lower limits -- conclusion

• Firm limit from common ancestor of all living
  people, and from clear symbolic behavior
• 100,000 years
• Fair degree of support for both speech and symbol
  capacity in Neanderthals.
• Common ancestor of us and Neanderthals lived
  gt500,000 years ago.
• Most likely age of some form of speech
• gt 500,000 years
• Homo Heidelbergensis? Homo erectus?

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A few key references

• Arensburg et al (1990). A reappraisal of the
  anatomical basis for speech in Middle Paleolithic
  hominids. Am J Phys Anthro 83137-146
• dErrico et al (2003). Archaeological evidence
  for the emergence of language, symbolism, and
  music an alternative multidisciplinary
  perspective. J World Prehistory 171-70
• Krings et al (1999). DNA sequence of the
  mitochondrial hypervariable region II from the
  Neanderthal type specimen. Proc Nat Acad Sci
  965581-5585
• MacLarnon, A. M. Hewitt, G. P. (1999). The
  evolution of human speech the role of enhanced
  breathing control. Am J Phys Anthro 109341-363
• Martínez et al (2004). Auditory capacities in
  Middle Pleistocene humans from the Sierra de
  Atapuerca in Spain. Proc Nat Acad Sci
  1019976-9981
• McBrearty, S. Brooks, A. (2000). The revolution
  that wasnt a new interpretation of the origin
  of modern human behavior. J Hum Evo 39453-563