W2 L2 Hominid Evolution Th Flashcards
Key skeletal changes to reduce the cost of bipedalism
Big toe reduced, straightened
Fingers become long and more slender
Pelvis shortened, more bowl-like than blade-like (helps support base of spine)
Spine curved to help lower back absorb shock
Femur bends inwards, knee straightened, patella central to joint
Connection with spinal column (foramen magnum) on underside of skull
-less robust upper arm
Change of stance for bipedialism
- Changing the skeleton reduces weight bearing on the spine and the neck
- Provides an advantage for individuals that are upright
- Australopithecus skeleton still differs though
When did we start to walk
Sahelanthropus tchadensis (7 Mya – Chad)
* Small skull
* Spinal column may connect to underside of skull
* Some evidence from other bones but debated
Australopithecus afarensis (3.2 Mya – Ethiopia)
* Small ape (30-45kg; 1.2m tall)
* Excellent skeleton that bears all
Evidence of Australopithecus afarensis walking
Bipedal footprints from Laetoli, Tanzania (3.5MYA) attributed to Australopithecus afarensis.
* Bipedal hominid, A. afarensis remains found nearby
* Footprints are heel to toe, walking like human
Human vs Chimp feet
Similar in some respects:
* Both have 52 foot bones (nearly 25% of all bones in body)
Different in others:
* Human feet are very inflexible providing better “push off” during walking
* Chimps adapted for climbling
Homo erectus walking like modern human
- 1.5 Mya footprints, found in Kenya
- Foot shape and pressure pattern almost identical to modern human
The evolution of human foot
- Big toe has not changed much
- Robust ankle ligaments supporting upright position
- Foot arch providing additional cushioning
- Soft tissue pads to provide cushion
Why did bipedalism evolve
Many possible explaination
* Improved foraging efficiency in grass-land (see above grass)
* Improved thermoregulation under the hot savanna sun (reduced surface area and possibly more air movement)
* Increased home range = increased foraging success
* Increased ability to use tools effectively (e.g. in hunting)
* Energetically efficient way of moving between food patches
* Increased meat consumption pushed selection for economy of movement
Human skeleton and running
- Over short distances, humans are one of the slowest mammals
- Even Usain Bolt would have been caught by a lion in less than 20 secs
- But we can run for 2-8 hours; no lion can
The evolution of tool use in the genus Homo
- Homo habilis (2.5myo) used simple stone tools
- Tools became more sophisticated over time
What’s so special about tool use?
- Humans use percussive techniques to shape tools into sharp points
- Creates stress on hand joints
- Have adaptations in their hands to deal with these
- Shape and proportion of hand increases performance when striking– in early humans may have advantaged in physical combat
Human using fire
Evidence from South Africa (1.5 Mya), Israel (700,000 ya) & numerous European sites (>500,000 ya)
fire and tool use and eating
-it changed the way we eat
-other primate are mainly vegetarian while human are omnivorous as fire allow us to process food
Fire changing our gut
Methods
* Collected data from 352-519 species
* Added body mass indices and diet they ate in the wild
* Controlled for phylogeny
* Diet positively related to gut size
* Different areas of the gut have a stronger relationship than other
Neaderthalis vs Homo sapiens
Stockier body
– Shorter legs
– Broader shoulders, hips
– Barrel chested
– Less slender hands, feet
