human evo

Hominid

Group that involves both living humans and apes & evolutionary ancestors

Hominin

Modern humans and extinct human ancestors (2legs)

Bipedalism

Habitual upright stance, first major step in humans as distinct group from apes

Great ape

Group of primates with long arms -> brachiating -> swinging of arms from branches Quadrepedal Includes chimpanzee, gorilla, orangutan

Primate

Order of mammals that includes humans, apes, monkeys and lemurs

Foot changes

Arched foot, big toe, robust heel

Arched foot

Acts as shock absorber, saves energy *flat feet

Big toe

In alignment with foot, more thrust when walking, uses energy for forward movement *big toe oppositional to grab things

Robust heel

And ankle, more long distance walking with no injury *gracile calcaneus

Leg changes

Valgus angle, longer legs than arms, wider femoral condyles, increased surface area of femur

Valgus angle

Knees are brought under pelvis by valgus angle, feet closer to center of gravity, better balance, more stability, less sway, conserves energy *head of femur and knee ends in vertical line- no angle, countrerbalance weight, sway movement

Longer legs relative to arms

Long femur, long bipedal strides, more propulsion while walking

Wider femoral condyles

Outer (lateral) bigger, prevents sideways movement of the knee *inner (medial) bigger

Increased surface area of the femur

On head of femur, reflects increased load on joint as more time spent walking on two legs

Pelvis changes

More bowl-shaped (wider and shorter) with a large surface area for more attachment sites for walking muscles (gluteus)

Pelvis change advantages

Effective balancing of the weight of torso over hips when walking upright, positions centre of gravity (behind lower back above legs), more energy efficient upright walking *small gluteous maximus, support body with arms

Skull changes

Reduction in nuchal crest, more centralised foramen magnum, flat face, early humans had zygomatic arch, (V), sticking out nose and chin

Reduction in nuchal crest

Reduced need for powerful neck muscles as the head is more balanced on the vertebrae (neck) *area for attachment large and large sagittal crest -> attachment for chewing muscles

More centralised foramen magnum

Allows a heavy skull to 'balance' on the spine without the need for muscles

What was happening at time?

Climate cooler and drier, lush forests reduced in size, grasslands dominated landscape

Spine changes

From c shaped to s shaped

S shaped spine

Humans, shock absorption, brings torso over hips, better weight distribution/balance

C shaped spine

Primates, counterbalance downward force of chest and organs when horizontal

Advantages of bipedalism

See further, carry babies, free hands to collect food, throw stones and wield sticks, keep cooler, look larger, greater display of sexual organs

Disadvantages of bipedalism

Back aches, painful birth, time to learn walk, varicose veins, undeveloped arch->painful flat feet

Theories of bipedalism

Provisioning model, energy saving model, savannah hypothesis, postural feeding hypothesis, thermoregulatory model

Hand development

Finger Curvature Thumb Length Thumb Strength Finger Proportions Fingertips Grip ability

Power grip definition

Whole-hand grasp where fingers and palm clamp an object against the palm. High force, low-fine control (e.g., hammering, carrying).

Precision grip definition

Grip between pad(s) of thumb and pad(s) of fingers. Low-to-moderate force, high fine control and dexterity / controlled positioning (e.g., threading, shaping).

Finger curvature

Changes from strongly curved to straight, -Transition from climbing trees to efficient manipulation of objects on the ground

Thumb Length

Changes from Short relative to fingers -> Long, fully opposable - Longer thumbs allow precise grips needed for tool-making and food preparation

Thumb Strength

Changes from Weak, limited muscle attachment -> Very strong, highly mobile - Stronger thumbs improve control and force when using tools

Finger Proportions

Changes from Long fingers compared to the palm -> Slender, proportionate fingers- balanced proportions increase dexterity and reduce injury risk when handling objects

Fingertips

Changes from Narrow, small pads -> Broad, flat pads with dense nerves - Sensitive, broad pads improve touch and precision handling

Grip ability

Changes from Mainly power grip (holding branches) -> Full power and precision grip - Precision grip enables advanced tool-making, art, and technology; power grip maintains strength tasks

Skull and brain changes

Brain size, Brow ridges, Forehead shape, Face projection, Jaw and teeth size, Chin, Foramen magnum position

Brain size

Changes from Small (≈400-500 cm³) -> Very large (≈1350 cm³) - Greater intelligence, planning, tool use, social behaviour

Brow ridges

Changes from Very pronounced -> Minimal - Lighter skull, more room for frontal brain expansion

Forehead spacing

Changes from Sloping -> High, rounded forehead - Space for enlarged frontal lobes (reasoning, language, planning)

Face projection

Changes from Protruding (prognathic) -> Flat face - Better balance of head on spine, improved speech articulation

Jaw and teeth size

Changes from Large jaws, large molars -> Small jaws, small teeth - Reflects cooking and tool use → less need for heavy chewing

Chin

Changes from Absent -> Well developed chin - Strengthens jaw, stabilises during speech and chewing

Foramen magnum position

Changes from Towards back of skull -> Central, underneath skull - Balances head upright for bipedal posture

Broca's area

Controls speech ie the muscles of the lips and vocal cords.

Wernicke's area

Area which interprets sounds (comprehension of language)

Provisioning Model definition

Freeing the hands to carry food and provisioning partners/offspring (e.g., carrying meat/plant foods from kill/forage sites to a safe place).

Provisioning Model advantages

Better infant survival, supports pair-bonding and division of labor; selection for efficient bipedal locomotion that facilitates carrying.

Energy-Saving Model definition

Walking on two legs uses less energy than knuckle-walking or quadrupedalism.

Energy-Saving Model advantages

More efficient long-distance travel, useful for foraging and migration.

Savannah Hypothesis definition

As forests gave way to open grasslands, upright walking became advantageous.

Savannah Hypothesis advantages

Better visibility over tall grass, easier to spot predators/prey, efficient movement in open areas.

Postural Feeding Hypothesis definition

Bipedalism first evolved for feeding while standing in trees.

Postural Feeding Hypothesis advantages

Reached food on small branches, freed hands to gather food.

Thermo-regulatory Model definition

Upright posture reduced heat stress in open environments.

Thermo-regulatory Model advantages

Less surface area exposed to direct sun, more wind exposure, improved cooling.