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Flashcards in CRANIAL EVOLUTION Deck (13)
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What is cephalic index

ratio of the maximum width of the head x 100 and divided by its maximum length.


What are the 3 classifications of the cephalic index

Dolicocephaly: head width is less than 75% of length

Mesocephaly: head width is between 75 and 85% of length

Brachycephaly: Head width is more than 80% of length


What are the cranial characteristics of Australopithecus

4.2-2.0 mya

300-500 cm3 capacity

Low forehead

Projecting face


What are the cranial characteristics of Australopithecus

2.7 - 1.1 mya

410 cm3 capacity

Broad cheekbones

Prominent brow ridges

Sagittal crest

Large zygomatic arch

More powerful mastication muscles like temporals and masseter (gives different cranial shape)


What are the cranial characteristics of homo erectus/ergaster

1.9-0.27 mya

Large brow ridges

Projecting nuchal torus (on occipital bone)

Wider at base

Braincase long and low

Supraorbital torus: lack of brow ridge function changes in facial expression


What are the cranial characteristics of Neanderthals

Long, flat and low braincase

Low receding forehead (more vertical)

Larch arching brow ridges

Projecting mid face

Lack of chin

Retromolar space

Occipital bun


What are some of the noted adaptation of Neanderthals similar to modern humans

Projecting face Could help heat flow through nasal passage

Not better adapted to sustain high loads on anterior dentition

Nasal passage improves warming of air but not better than humans

Higher capacity of moving air due to energetically demanding lifestyle and higher calorific intakes


What are the cranial characteristics of early humans

Short, round and high brain case

High forehead

Smaller nose

Presence of chin

No retromolar space

Rounded occipital


Different nasal morphology (smaller than neanderthals)


What are the implications of early humans having chins

Mechanical significance in chewing

Needed for resistance to loads during incision and mastication


What is palaeoneurology

Study of brain evolution by analysis of brain endocasts to determine endocranial traits and volumes.


What is an endocast

Internal cast of the cranial vault

shows external brain features impressed on cranial bones

can observe trends in cranial capacity changes


What are the average cranial capacities for the 3 phases of development

Phase 1: early hominins = 450-530

Phase 2: early homo = 600-1200 (H habilis to H erectus)

Phase 3: late homo = 1200-1500 (now 1400 modern human)


What are the possible reasons behind the differences in neanderthal and modern human cranial capacity

Neanderthal large brain could be adaptation to cold envrionments

Differences due to changes in brain growth after birth

Obstetric dilemma: Head size smaller than pelvic inlet so brain growth occurs after birth