Habitual bipedalism

• The single most important characteristic for hominine evolution
• Adaptations can be seen in the foramen magnum, spine, pelvis, legs & feet
• Derived traits for bipedalsm all keep our center of gravity directly beneath us

• Larger, with more folds & surface area
• Slowly developing around 6 mya with a big jump around 2 mya

• Stone tools from about 2 mya
• Shows abstract thought & planning
• Same cognitive abilities required for language language, but no evidence

• It takes us longer to reach different stages of development than other animals
• We have so much more to learn than other organisms, it takes a long time to acquire all the information we need to survive
• Our intelligence allows us to be successful at living a longer lifespan

• Easiest fossils to find
• Give us information about diet, which tells us about the environment, sexual dimorphism & social structure
• Canines get smaller, molars get bigger, enamel gets thicker

Ocurred slowly over time in a mosaic pattern

1.  Habitual bipedalism

2.  Larger brains

3.  Material culture & language

4.  Slower life history

5.  Dental differences

Mosaic evolution

The concept that major evolutionary changes tend to take place in stages, not all at once.  It's a pattern of evolution in which the rates of evolution in functional systems vary from each other.

• 23-5 mya
• Significant environment change
• The planet gets cooler & drier
• Formation of mountain glaciers & polar ice caps
• Multiple effects of cooling: overall decrease in rainfall, rainfall become more seasonal, forests shrunk, woodland areas opened up & savannas expanded
• Created new niches to be filled by adaptive radiation

• 5-2 mya
• Cooling from Miocene continues
• Retreating forests & increasing grasslands create a mosaic environment
• Changes animals' access to resources
• We think a lot took place here for our ancestors

All traits keep the center of gravity centered beneath us

1.  Foramen magnum

2.  Spinal column

3.  Pelvis

4.  Legs

5.  Feet

• Encases the head from the top & wraps around most of the back of the skull
• Placement allows our heads to naturally sit on top of our necks with our eyes pointed straight ahead

• Changes from a C curve to an S curve
• Keeps the center of gravity over the pelvis
• S curve is great for absorbing shock

• Shorter & wider than apes
• Shape creates a bowl for our organs to sit in

• Femur joint has a wider base & comes out further form the pelvis, then angles inward
• Knee joint locks which allows for more absorption of pressure
• Legs are longer relative to body size

• Big toe is smaller, pushed in to the rest of the toes
• Has lost grasping abilities, gained balance
• Arched foot supports weight & absorbs shock
• Allows us to push off with our big toe when we run & jump

1. Savanna theory
2. Relief from heat stress
3. Provisioning mates
4. Energy efficiency
5. Increased ability to see predators, prey, resources & direction

Hominine ancestors were forced out of the trees with the climate shift in the environment.  With the forests decreased, & the grasslands expanded, those who developed bipedalism survived.  Not a likely theory because evidence for bipedalism has been found in areas that were wet & forested at the time.

Less of the body's surface area is exposed to the sun, more is exposed to cooling winds

• Being able to carry things made it possible to exploit resources over a larger area
• Transport of food to mates & offspring; ties into reproductive success
• If you can carry more food to mates, you are likely to get more mates
• Females could carry food & offspring at the same time

• Ability to cover greater distances with less energy
• Not only necessary in grasslands, but in helpful forests where resources are dispersed

1. Pre-Australopithecines
2. Australopithecines
3. Homo

1. Sahelanthropus tchadensis: 7 mya, Chad; furthest west fossil ever found; could suggest westward expansion; predates savanna hypothesis - likely lived in a wet, forested environment; not sure it's a hominine, but if it is, it pushes our ancestry line back about 2.5 mya
2. Orrorin tugenensis: 6 mya, Kenya; not sure it's a hominine, but if it is, it pushes our ancestry line back about 1.5 mya; Likely a woodland/forest habitat - predates savanna hypothesis
3. Ardipithecus ramidus kadabba: 5.8 mya; little evidence
4. Ardipithecus ramidus ramidus:  4.4 mya, Aramis, Ethiopia; earliest widely accepted bipedal hominine; intermediate form - protruding big toe - probably not very efficient biped; also probably forest dweller

Australopithecines

All Australopithecines were fully bipedal

1. A. anamensis:  4.2 mya, Kenya; earliest species widely accepted as an australopithecine
   
2. A. afarensis:  3.8 mya, Laetoli, Tanzania & Ethiopia; apelike features; very sexually dimorphic
3. A. africanus:  3 mya, South Africa; the Tuang Baby; 1st australopithecine discovered; lots of evidence since initial discovery; gracile
4. A. garhi:  2.5 mya, Ethiopia; possible toolmaker; gracile
5. A. aethiopicus:  2.5 mya, East Africa; robust
6. A. boisei:  2.2 mya, East Africa; very robust
7. A. robustus:  1.8 mya, South Africa; robust

• 2.4 mya, Olduvai Gorge, East Africa
• The earliest member of our genus
• Lots of variability; more robust versions sometimes called H. rudolfensis
• 1st significant increase in brain size; 20-30% bigger than australopithecines
• 1st appearance of frontal lobe, reorganization of the brain, more surface area created by folds
• Larger neocortex
• Scavengers

1.  Sahelanthropus tchadensis: 7 mya, Chad

2.  Orrorin tugenensis: 6 mya, Kenya

3.  Ardipithecus ramidus kadabba: 5.8 mya

4.  Ardipithecus ramidus ramidus: 4.4 mya

5.  A. anamensis: 4.2 mya, Kenya

6.  A. afarensis: 3.8 mya, East Africa

7.  A. africanus: 3 mya, South Africa

8.  A. garhi: 2.5 mya, Ethiopia

9.  A. aethiopicus: 2.5 mya, East Africa

10.  A. boisei: 2.2 mya, East Africa

11.  A. robustus: 1.8 mya, South Africa

12.  Homo habilis: 2.4 mya, East Africa

1. A. aethiopicus
2. A. boisei
3. A. robustus

1.  A. africanus

2.  A. garhi

• Located at the Great Rift Valley in Tanzania
• Incredible amount of fossils found here
• Geological processes that ocurred here created an environment great for fossilization

• 3.5 mya, Northern Tanzania
• Footprints of 2 hominines walking in ash
• Best evidence for early bipedalism, shows us these individuals were fully adapted for bipedalism

• Earliest tools
• Flaked & chipped rocks to be used as hammer stones, scrapers & choppers
• 2.4 mya, same time as A. gahri and H. habilis
• Tools show capability of abstract thought & problem solving