• Size and Shape relationship

– Part of an organisms adaptation

• Expectations: Large animals

– Relatively low energy requirements – slower metabolism

– Lower quality diet – more abundant

– Larger geographic ranges

– Relatively weaker bones (can an elephant jump?)

– Longer life span

– Fewer offspring – more investment

– Etc.

• Allometry – The independent variable increases at a different rate than the dependant variable

– Ex: Body size and limb size/shape

Positive Allometry - the dependent variable increases at a higher rate than the independent one

Isometry - the dependent variable increase as the same rate as the independent one

Negative allometry-the dependent variable increases at a lower rate than the independent one

• Bergmann’s Rule– For a widely dispersed warm blooded species: those in cold climates are heavier (higher body mass)

• Allen’s Rule– For a widely dispersed warm blooded species: those in cold climates have shorter limbs

Cold environment animals will have less surface area to body mass ratio and thus conserve heat loss, while warm environment animals will have a higher surface area to body mass ratio and increase heat loss.

• The study of human evolution tries to trace the development of those features that make us uniquely human

• We often put those species that exhibit these features in the hominin, or human, ancestral lineage.

• But what are those features? Particularly, what could we see in morphology? How do we differ from great apes, our closest cousins?

-Brain features and intelligence

-Bipedalism

-Jaws and tooth morphology

-
Changing life history

-Change in size, increase over time

-Change in structure and organization

Cerebral hemisphere

Brain stem

Cerebellum

-Trend toward increase, esp. in cerebral cortex (grey matter)…memory and visual mapping

-
3x bigger than predicted for body size (These are studies of allometry)

-Is the human brain an advanced primate brain- NO, it is something different with different specializations

-
Deacon and The Symbolic Species: prefrontal area is especially large, 6x larger than predicted

-
Prefrontal: planning, choosing, predicting future events, emotions

-
Hominin brain is a primate brain co-opted for language, symbolism

-We share two areas with non-human primates

Brodmann’s area -Syntax

Planum temporale -sound location/ speech production

-BOTH areas are advanced in humans Speech areas

is the cortical area just posterior to the auditory cortex, one of the most important functional areas for language

• Broca’s area- primarily associated with syntax, or giving groups of words meaning, also interpreting others actions, gestures

• Wernicke’s area- associated with comprehension of speech

• Each has strong links to temporal lobe, which does high level auditory processing, and some complex visual processing

Lateralization- use of specific sides of the brain for specific tasks/processes

Language and lateralization- Not unique to hominins, but extreme in hominins

-writing and spatial relationships on right

-language and motor speech on left

Links between hemispheres- language and handedness develop at the same time; is this why so many people are right handed?

Lateralization allows for continued specialization of brain as specific areas develop

-Efficient bipedalism truly different adaptation; no other extant species does this quite like we do

-Chest and spine form

-Pelvic form

-Relative limb proportions

-Skeletal & muscular changes

-Earliest true hominin character?

Low energy stride use leg weight and upper body as pendulum

Cycle: toe off(stance), swing phase, heel strike

Head balance: foramen magnum cervical curvature

Less funnel shaped

Shorter

Decreasing in the broad shape; less emphasis on the upper body for brachiation…arms take on a different role

Big toe (hallux)-adduction, or aligned against foot

Arch- acts as springboard

Heel-enlarged for support impact

Humans- ankle gets all the torque

Chimps- hips get all the torgue

-Loss of projecting, slashing canine

-Reduction in incisors

-Predominance of grinding teeth

-Side - to- side chewing cycle

-Canine eruption less delayed

Changes in craniofacial proportions Muscles: Temporalis, Masseter

Much less of the human skull is used for an attachment of the chewing muscles

• Timing of life stages has a lot to do with life history strategies.

• Influences are seen in body size, metabolism, brain size, number of offspring, investment, and mortality.

• r–k Selection – Gorilla = k – Mouse = r

large body size, small body size

• Humans grow slowly

– 18yrs for skeletal maturity (chimps 12yrs)

• Long life span relative to body size

• Significant post-reproductive life (post menopausal)

– Working grandmother hypothesis

•Humans are very precocious mentally

• Humans are very altricial physically

– We should have a longer gestation,we have giant brains

• Trade-off btwn width of female hips, size of baby's brain, and maturity (dependence)

Precocious=independent, Altricial=dependent