Anthro Lecture 6 2.5

Primate vs Hominid vs Hominin
- Primate: biological order that includes apes, monkeys, prosimians, humans & ancestors, and closely related animals
  - Over 300 living species of primate
  - Usually poor sense of smell
  - Usually relatively flat, prehensile hands and feet
  - Usually flexible shoulders & hips
- Hominids descended from the common ancestor of all Great Apes
  - Usually share at least 97% of DNA with humans
  - Usually can at least stand on two legs
  - Larger brains
  - Can make tools
  - Usually can use/understand a little language
- Hominins are a part of the lineage leading to Homo Sapiens
  - More closely related to humans than to chimpanzees
  - Usually can use/understand a little language
- Humans are all three
Environmental Context:
- Pliocene: 5.3-2.5/1.75 mya
  - Slightly warmer than today on average
    - Noticeble cooling trend
  - Sea lvl 80 ft higher on average
  - North & South America become connected
  - Around 3 mya, glaciation began to occur
  - Animals:
    - Ancestors of zebra
    - Ancestors of lions
    - Predators
- Pleistocene: Ice Age, 2.5 mya-12 kya
- East Africa: where most human evolution happened
  - Africa's Great Rift Valley:
    - Earth is ripping tectonic plates apart from each other, creating new tectonic plate
    - Reconstructing the environment: Deep Sea Cores
    - Starting around 20 mya, the forests and jungles of east Africa began to recede and were replaced by savannas
      - Savannas: grasslands w/occasional tree growth
      - By 6 mya the savanna is the dominant environment in east Africa. Thus, ur ancestors who had adapted to life in the trees had to adapt to a drier, less forested ecosystem
        
        Walking on 2 legs, more energy efficient
        
        Bowl-shaped pelvis & flexible torso
        
        Human (Homo) vs Chimp (Pan)
        
        C vs S-shaped spine
        
        How to tell if a skeleton was bipedal:
        
        Pelvis shape
        
        Skull (foramen magnum)
        
        Bipedalism developed by 4 mya; possibly 6 mya or earlier
        
        High-quality plant food were widely dispersed over the savanna hominins expanded their food range to include more meat, perhaps during plant scarcity. In mammals, this is associated w/larger brains relative to body size
        
        Accessing food becomes more complex bc environment; intelligence selected for
        
        Sexual dimorphism is reduced to accommodate giving birth to large-brained children; women get larger
        
        Additionally, our brains and those of our hominin ancestors are not well-developed at birth. Thus, while it takes longer for us to raise our offspring, it makes giving birth easier
Hominins: Worldbuilding ideas
- Sahelanthropus tchadensis (5-7 mya)
  - Unique bc he was discovered in north-central Africa and not east Africa
  - Maybe a biped
- Australopithecus afarensis (3-4 mya)
  - 3.5-5.5 ft tall hominin who inhabited East Africa.
  - Bowl-shaped pelvis
  - Brains are chimp-sized (400 cc)
    - "Walk good comes before think good"
  - "Lucy" Worldbuilding ideas
    - Bipedal, but retained earlier tree-navigating traits; ironically, she may have died falling from a tree
  - Footprints in volcanic ash (Laetoli footprints) Worldbuilding ideas
    - Mary Leakey & Paul Abell discovered two trails of footprints preserved in volcanic ash in the same sediment layer as A. afarensis fossils
    - Trails is abt 90 ft long and contains 84 individual prints
- 7-9 known Australopithecine species
Paleoanthropologists: study of the origins and predecessors of the present human species, using fossils and other remains