human evolution Flashcards
What did the diet of chimpanzees mainly comprise of? And how did this affect their facial structure?
Tough fibrous plant material so required powerful chewing forces generated by large muscles
What selection pressure resulted in quadrepeds moving to bipeds?
Climate change - Africa became cooler and drier, reduced forestation to more grasslands, deserts and savannah ecosystems.
Climbing biped was advantageous as they could live in both habitats and occupy a wider niche. Gather more food, less competition for resources (outcompete other species that cannot carry out bipedalism), increase chances of survival and reproductive success
Changes in hallux (big toe)
Q: opposable hallux to allow grasping during tree climbing, aid arboreal lifestyle
B: hallux in-line and non-opposable, provides forward thrust for bipedalism and aids with balance
Changes in feet
Q: flat foot
B: arched foot, acts as a shock absorber and spring to propel forward
Changes in foramen magnum
Q: positioned back of the skull, positions head forwards when moving quadrupedally
B: centralised, head balanced on top of spine over the centre of gravity so less energy required to support the head
Changes in spine
Q: C-shaped spine, weight of abdomen supported on arched spine while on four limbs
B: S-shaped spine, acts as shock absorber, centre of gravity positioned above pelvis so less energy to support head
Changes in ribcage
Q: cone shaped, house large gut and allow wide range of motion for brachiation
B: barrel shaped, allow arms to swing side to side to assist with balance when walking
Changes in pelvis
Q: narrow and flat
B: shorter and broader, bowl shaped, allows for bigger head during birth
Changes in valgus angle
Q: large valgus angle
B: smaller valgus angle, places feet directly below centre of gravity, allows for stable bipedal locomotion and conservation of energy whilst standing
Changes in arm:leg ratio
Q: longer arms for brachiation
B: longer legs to cover more ground per stride, travel longer distances and increase energy efficiency
Changes in fingers
Q: longer curved fingers, stronger grip on branches
B: shorter straight fingers, increases ability for power and precision grips for tool making
Explain the selection pressure for finer motor control and precise manipulation of objects
More developed hand/wrist muscles have an adaptive advantage → create more sophisticated tools → more sophisticated hunting techniques → larger success rate of collecting food → greater chance of survival
Positive feedback loop between bipedalism and hand dexterity.
What are the four changes to the endrocranium?
- Increase in brain size
- Increase in cortical tissue (cerebrum)
- Increase infolding of cerebellum
- Development of Broca’s and Wornicke’s areas
Why is an increase in brain size good?
Tool making abilities increase → improved hunting efficiency → greater food supply and resources for a larger brain
What is the cortical tissue (cerebrum) responsible for?
Higher brain function (abstract thought, finer motor control, complex thinking and actions)
What is the cerebellum responsible for?
Balance and muscle coordination
What are the Broca’s and Wornicke’s areas responsible for?
Broca’s = production of speech
Wornicke’s = comprehension of speech
Why are the Broca’s and Wornicke’s areas beneficial?
Increase speech and language ability → improve communication → greater efficiency during group hunting + elders can pass down knowledge and experience to younger ones
What are the 4 advantages of bipedalism?
Hands free → able to carry items eg. young or bring food back to home base + make tools
More energy efficient locomotion
- travel longer distances → outcompete other primates for resources
- more energy available for other activities
Easier to locate food and predatorss (disadvantage easier to be seen by predators)
60% less surface area exposed to the sun + stronger air currents above ground → keep cool → better thermoregulation on hot African grasslands
What are the 6 disadvantages of bipedalism?
- Childbirth is a risky process
- Increased chance of hernias
- Back ache + slipped discs (S-shaped spine → larger load on lower back)
- Strain standing on two legs → arched feet collapse
- Varicose veins (veins become enlarged and twisted) → susceptible to cuts and grazes
Reduced ability to travel distances + decreased speed (painful) → gather less resources for survival + increased chance of predation
Biological evolution
The transmission of genetic material from parent to offspring
Cultural evolution
The change in human culture through the transmission of learned behaviour, ideas and knowledge from one generation to another
What trend did tools show over time?
- more specialised
- sharper, more refined, longer blades
- increase in variety and quality of materials
- more complex, more imagination
- more blows/strikes
Oldowan tools (who, how many blows, description)
Homo habilis
~ 6 blows
Stone tools with several flakes knocked off one side by heavy blows by another rock
Acheulian tools (who, how many blows, description)
Homo erectus
~ 50 blows
Stone tools with flakes struck off both sides (biface), long sharp edges
Mousterian tools (who, how many blows, description)
Homo neanderthalensis
~ 150 blows
Levallois technique used to sharpen flakes
Specialised tools eg. spears and axes
Upper Paleolithic tools (who, how many blows, description)
Homo sapiens
~ 250 blows
Specialised, finer and composite tools
Huge range of tools, very job specific
What are the 5 advantages of tools?
- Skin animals for clothes and shelter → live in cold places/new environments + less sickness
- Hunt bigger animals → more meat/energy
- Access to wider variety of food sources → higher quality diet eg. meat
- Better able to manipulate materials → more complex shelters made → large groups to live together
- Change in skull (don’t need big teeth/jaws) → increased brain size + cognitive ability
Who was the first to use fire?
Homo erectus
What are the advantages of fire?
- Lengthens day (light source at night)
- Cooking
- Better weapons/tools
4.Protection from predators (scare predators away) - Provides warmth (migrate to colder areas)
Why is longer day length provided by fire beneficial?
Enables activities to continue after dark -more time to make tools, learn language, teach others
Time to socialise - binds group together for cooperation
Why is cooking beneficial?
Soften foods and easier to chew → no need to grow large jaw/teeth/ muscles → energy can be used to run a bigger brain
Detoxifies food and kills pathogens in meat → prevent illness and death
Makes food more digestible → greater energy intake from same amount of food
Preserve meat (smoking) → lower chance of starvation when food is scarce
Poisonous foods when raw can be eaten when cooked → wider variety of food
How does fire improve hunting?
Fire hardened spear tips → sharper
Hunt with fire → stampede animals → more efficient and successful hunting → more food
What are the disadvantages of fire?
Lots of energy to make
May burn yourself
Destroys ecology
Attracts predators (beacon)
Smoke/fire (tuberculosis)
