Prelim 2 Flashcards
Lectures 10-18
What are the costs of bigger body size?
Need more food
What are the 3 benefits of bigger body size?
- Need food less often
- Better at intra-species competition for resources and less vulnerable to predators
- Locomotion - once moving, can run/walk long distances
Benefits of larger brains/CBS
- Social intelligence
- Technological intelligence
- Control of fire
Costs of larger brains/increased CBS
- Premature/helpless infants
- Lots of energy needed
- Tradeoff - smaller guts & higher quality diets needed
Expensive Tissue Hypothesis
Theory that increased brain size is afforded through decreased gut size - acc. Wrangham, this is possible due to cooking
Impact of helpless infants
Women need constant help and must carry infant
Morphological differences between H. erectus & sapiens
Below head - basically the same
H. erectus has smaller brain and more prognathic
Radiation
Rapid expansion of many new, related species (due to natural selection)
Phylogenetic Species Concept
Use physical traits and “clusters” of similar traits to group species together
Miocene
23-5.3 MYA, more cooling, radiation of ape species - human evo. from apes begins at end of this
Sources of variation within species
Age, sex, geography
Derived characteristics
Characteristics that deviate from past ancestors
How can we date human evolution?
- Fossils - different strata of Earth
- Molecular clock - DNA comparison (e.g. between humans and chimps)
Adaptive shifts in hominid evolution
- Locomotion
- Diet & dentition
- Brain size increase
Obstacles to bipedalism
- Loss of balance/stability
- Difficulty of pulling leg up
- Less speed initially
Indications of bipedalism in fossils (5)
Foot - parallel big toe, 2 arches
Leg - upper femur angle
Pelvis - bowl-shaped & outward flare
Spine - double curve (vertebrae)
Skull - Foramen Magnum at bottom center
Ardipithecus ramidus time + place
4.4 MYA, Ethiopia
Ardipithecus ramidus morphology + behavior
Small, bipedal climbers with changing dentition
Australopithecus afarensis morphology + behavior
“Bipedal apes”
Small, long armed, flared pelvis, no grasping big toe (likely poor climbers)
Australopithecus afarensis time + place
4-3 MYA, Ethiopia
First adaptive shift
Bipedalism
Second adaptive shift
Diet + dentition
Gracile species
Huge back teeth
Australopithecus africanus and A. sediba
Tiny, bipedal small-brained apes with giant molars
3-1.9 MYA
Robust species
REALLY huge back teeth
Paranthropus aethiopicus, boisei, robustus
Huge chewing muscles, sagittal crest and bigger brains
Died out(?)
2.5-1.8 MYA
Theories of bipedal advantage
- Reach fruit above head
- Scan for predators/resources
- Free hands (for infants, food, tools)
- More efficient locomotion (maybe not)
- Heat stress in savanna
Early hominid diets
Hard foods - USOs, nuts
More flexibility in savanna - survive dry season and scattered resources
Types of diet data
- Chemical - isotopes & proportions of elements
- Archaeological - tool marks on bones, teeth fossils
- Ethological - examine chimp use of tools (can dig for USOs)
Homo habilis morphology + behavior
- Big brain to body ratio
- First to fully benefit from bipedalism (Bigger bodies, longer legs, no divergent big toe)
- Loss of Sagittal crest, but big molars
- Extensive tool use (“handyman”)
H. naledi
Super recent discovery - possible offshoot of paranthropus, b/c brains are way too small
Throws everything into question
Last great adaptive shift
H. erectus: new range, ecology, genus
H. erectus range
Africa –> Eurasia, Indonesia
H. erectus morphology
Postcranium, essentially modern
Less prognathic and bigger-skulled than H. habilis
Societal implications of helpless infants
Mothers need much more help and must constantly attend infants, plus need more energy/food
Acheulean tools
Second tool industry
Hand axes, cleavers
Made by intentionally shaping multiple sides of a rock
Oldowan tools
First tool industry
Stones with flakes taken off
Archaic H. sapiens characteristics
- Habitual use of fire
- Better tools
- Big game hunting
What ecological changes led to the emergence of hominins?
Global drying and reduction of rainforests –> hominins move to savanna
Pleistocene
2.5-.01 MYA
“Ice Age” aka many glaciers, up to 70-80% of surface
Sea levels fell & land bridges
When did habitual fire use begin?
Direct evidence - 400,000 YA
Hearths (repeat burning) and concentrated, burnt artifacts prove
Early archaic H. sapiens
400,000 - 125,000 YA
Brain size into modern range
Reduced posterior dentition but big anterior teeth
Massive brow ridge
Levallois tools
Third tool industry - early H. sapiens
Made out of super sharp stone flakes
Sometimes lashed to a shaft to create 7ft spears
What are the implications of big game hunting?
Additional intelligence to cooperate, plan, preserve meat
What are the results of range expansion?
Flexibility and generalism
When did bipedalism begin? Which species is associated with this?
~4 MYA, A. ramidus
When did dentition begin to change? Which species is associated with this?
~2.5-1 MYA, Paranthropus genus and A. africanus/sediba
When did brains and bodies grow bigger? Which species is associated with this?
~2 MYA, H. habilis/erectus
Recent Replacement
Splitters
H. erectus travels, dies out in other continents
H. sapiens evolves in Africa and expands to other continents, maybe pushing out old erectus species
Multi-Regional Evolution
Lumpers
H. erectus leaves Africa, evolves into H. sapiens separately
Gene flow ensures no speciation
Neanderthal time + place
400,000 - 30,000 YA in Europe and Middle East
Neanderthal morphology + behavior
Sloping forehead, big nose, no chin, occipital bun at back of skull
Short, stocky, thick bones
No evidence of diff. brain function
The Neanderthal Question
Are Neanderthals
1. a different species from us which developed from H. erectus (RR)?
2. a subspecies, but still Homo sapiens (MRE)
Flores hominins time + place
700,000 - 13,000 YA
Indonesia
Flores hominins morphology + behavior
Super tiny, simple tool use, no gene flow with other populations
How did humans reach the Americas?
Land bridge during Pleistocene (low sea levels) between Russia and Alaska, then walking/rafting to Patagonia
