Homo X


Share ancestor with humans, neanderthals ~5mya

Lived 400k to 40k years ago ; share common ancestor with humans ~400kya


Sapiens (us) are <150k years old

Brain size

Same as Lucy- bipedal ape of 3+mya (400cc)

Larger than homo Sapiens (~+20%)


>hippocampus, neocortex than ape

Birth Process adjusts for larger brain and bipedalism . Neonate brain size proportional to adult's? larger opening relative to brain, quad.., solitary in tree or brush similar to humans in size but perhaps easier to exit womb? very close fit thru cervix, pregnant human requires social support ; infant premature and helpless.

Cerebral asymmetry

Slight right hand pref in some  situations; no clear species preferences

some brain asymmetry

Right handed, larger left hemisphere

(maybe true for h.habilis even earlier) (more)

Same as neanderthal? Could size & assymmetry progress with increasing tool use? (see below)

neural language-related circuits very inflexible "voluntary" control of vocal tract; would never play Bach on piano! ?

flexible cortical and subcortical control of vocal tract; fingers too

Human brain may be shaped by its early language environment via the "Baldwin effect" - coevolution.

cf Mokan myth

analogy to Creoles emerging from pidgins???

little or no natural referential vocalization; subcortical control;

some gestures ?

proto-human language? referential language without structure?

Structure invented but what does it add?

Creativity? Speed? compatibility with Mentalese?

L aids memory, learning, form ToM.

"mirror" neurons yes but little vocal tract mimicry? ? yes- high resolution vocal mimicry
FOX2P and other genes not like human like humans? ? FOX2P may enable brain/vocal/hand flexibility

  Hand & grip

  depends a bit on species; good for primates, less than humans, esp opposable thumb, pinky questions?

  looks similar to human but could they play the piano? Control issue?

  opposable thumb, precision grip, pinky controlled stick grip

Use tools? Adaptation to climate change?

(does language promote refinement?)

Limited usage; no progressive refinement; recent report of stabbing "spears"

stabbing spears, many stone cutting tools, not much refinement either.

Have precision grip.

rapid invention and continued refinement of abstract "mind" tools as well as physical ones.

Use representations?


Language appears to at least reflect an extremely flexible, extendable rep system.

Possible limited internal imagery (Kohler's insight)

No external representations

Some suggested by burials

Yes- external at least 30K years ago ; with extensive "mind tools" including language. Great flexibility in internal imagery, inner speech.

"grain" (resolution) and flexibility of sensory-motor-cognitive representations

Kohler's "insight"

limited and dependent on experience

highly visual



a primary function of larger brain

decompose perceptual/cognitive objects into manipulable components

representations modified by "pretend" and others language before 2y.

motor precision trade-off with strength?

recursion in L enables picking out objects at an arbitrarily fine level of precision (Pinker, 368)-- almost like fingers!

Consider the similar recursion in "ToM" language. "B knows S believes that F thinks that ...."


None beyond limited mammalian

message set -- largely a closed system (few novel messages) .

Language is a form of communication; not all communication is language.


Can learn hundreds of HBC symbols; some linear combinations; no phrases.

No obvious "openness" in natural settings beyond classical/operant conditioning (rare?).

Possibly some limited speech? Open to new messages?

Paabo claims they have the FOX2P gene, like humans, but not the same one as chimps.

Yes >100,000 years ago.  Writing 5000 years ago. An "open" system with

Syntactic language where novel meanings are built out primitive meaning units --also open--(new words) in grammatical relationships


New creations at all levels- morphemes, words, phrases.

Vocal tracts


detailed from Grays anatomy

relatively large tongue, high larynx, likely very poor motor control  (See VickiŐs training.)


hyoid bone doesn't descend as in humans

Smaller tract, larger tongue,  difficulty shutting off nasal cavity, slow speed

hyoid bone? yes

Midway between chimp and human?


Smaller tongue, lower larynx, very flexible tongue and tract.  Rapid speed.

hyoid yes . Modern human vocal tract maybe as recent as 50k-100k years.

Repositioning is costly.

Tongue large unwieldy ; little descent of larynx more controllable ; similarity to human descent debated extremely flexible; tongue and larynx descends for first 6 years--or less.
hypoglossal nerve controversial comparisons   necessary for vocal speech

Inner ear system

(balance & cluminess)

< humans


Large for primate