Human Bio - Hominid Evolution

prognathism in apes vs humans

in apes:

• faces are prognathic

• jaws are longer and stick outward

in humans:

• prognathism is reduced

• faces are flat

diastema in apes vs humans

in apes:

• Presence of diastema (a gap between teeth to accommodate canines)

in humans:

• No diastema – to allow for more space in mouth to articulate speech

dentition in apes vs human

in apes:

• jaws are V-shaped to allow for chomping raw vegetation

• presence of a simian shelf

• large canines and large teeth sizes (for aggression and fighting)

in humans:

• Jaws are U shaped to allow for a more varied diet

• No simian shelf

• Smaller canines and reduced teeth size and molars (due to use of tools instead of teeth)

brain size in apes vs humans

in apes:

• ape brains range from 400cm^3 to 500cm^3

• smaller cranial capacity

in humans:

• human brains range from 900cm^3 to 2220cm^3

• larger cranial capacity (to house the bigger brain)

convolutions in brains apes vs humans

in apes:

• less convolutions/folds -> reduced surface area limits cognitive abilities

in humans:

• more convolutions/folds -> higher surface area means increased cognitive abilities

specialised language areas in apes vs humans

in apes:

• No specialised language areas; instead they communicate with basic gestures   

in humans:

• Presence of the Broca’s area and Wernicke’s area to produce and understand complex language

foramen magnum in apes vs humans

in apes:

• Foramen magnum is positioned more towards the back → head sticks out & supported by neck muscles

in humans:

• Foramen magnum centrally placed at the bottom of the skull → skull balances on vertebral column

pelvis in apes vs humans

in apes:

• longer and narrow pelvis to support greater mobility (e.g. climbing, swinging)

in humans:

• shorter & wider bowl shaped pelvis to support abdominal organs and carry foetus during pregnancy (for women)

spine in apes vs humans

in apes:

• “C-shaped” spine -> supports quadrupedal gait

in humans:

• “S-shaped” spine –> to support a striding gait & maintain body’s centre of gravity

legs and glutes in apes vs humans

in apes:

• smaller glutes used more for climbing and swinging

• long arms, short legs -> supports quadrupedal gait

in humans:

• larger, modified gluteus muscles

• Long legs, short arms -> supports striding gait

femurs in apes vs humans

in apes:

• femurs are vertical –> no carrying angle, weight distributed on all fours for quadrupedal gait

in humans:

• femurs angle inward -> distributes weight and brings it towards outside of femur -> better stability and striding gait

feet in apes vs humans

in apes:

• opposable toes -> can grip branches with feet

• Flat feet & no arches -> better power grip for climbing and swinging in arboreal environments

in humans:

• non-opposable toes (unique to humans)

• transversal arch (to act as shock absorber) and longitudinal arch (to distribute weight evenly when walking)