Constraining the time when language evolved

Sverker Johansson

School of Education & Communication

University of Jönköping, Sweden

Precise time of language emergence cannot be determined

Upper and lower limits can be set

Time limits add constraints to theorizing about language origins

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

Upper limits IINon-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!

Lower limitsTrivial 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.

Lower limits IILanguage 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.

Lower limits III -- Anatomy

•Speech organs

•Hearing organs

•Brain

•Neural connections

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

Anatomy II – Hearing organs Human ears tuned for 3-5 kHz sensitivity compared with chimps.

Adaptation for speech perception? (but see also Zuidema & O’Donnell 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)

Chimp(green)

H heidelbergensis(red, purple)

Martínez et al (2004) PNAS 101(27)9976

Anatomy III – Brain Gross anatomy of brain visible in fossils. The age of e.g. Broca’s 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.

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.

Anatomy conclusionsSeveral 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.

Lower limits III -- Symbolics

• Art and ornaments imply symbolic capacity?

• Advanced creative tool making?

• Cognitive “Big Bang” 40,000 years ago?

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).

Symbols II – Pre-40k culture

Beads (ostrich eggs), 52,000 BP

McBrearty & Brooks (2000)

Used pigment chunk, >200,000 years BP

Barham (2002) Curr Anthro 44:627

Engraved ochre, 77,000 years BP

Yellen et al (1995) Science 268:553d’Errico et al

Barbed bone tools, Katanda, 90,000 years BP

Symbols III – Pre-sapiens art?• 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.

Yellen et al (1995) Science 268:553 Bednarik (2003) Curr Anthro 44:405

Figurine – or just funny rock?

Neanderthal ornaments? 33,000 BPd’Errico et al (2003) JWP 17:1

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 268:553

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

>500,000 years ago.• Most likely age of some form of speech:

> 500,000 yearsHomo Heidelbergensis? Homo erectus?

A few key references• Arensburg et al (1990). A reappraisal of the anatomical basis for speech in

Middle Paleolithic hominids. Am J Phys Anthro 83:137-146• d’Errico et al (2003). Archaeological evidence for the emergence of

language, symbolism, and music —an alternative multidisciplinary perspective. J World Prehistory 17:1-70

• Krings et al (1999). DNA sequence of the mitochondrial hypervariable region II from the Neanderthal type specimen. Proc Nat Acad Sci 96:5581-5585

• MacLarnon, A. M. & Hewitt, G. P. (1999). The evolution of human speech: the role of enhanced breathing control. Am J Phys Anthro 109:341-363

• Martínez et al (2004). Auditory capacities in Middle Pleistocene humans from the Sierra de Atapuerca in Spain. Proc Nat Acad Sci 101:9976-9981

• McBrearty, S. & Brooks, A. (2000). The revolution that wasn’t: a new interpretation of the origin of modern human behavior. J Hum Evo 39:453-563