Exam 1, Hominins

Where did the ancestors of the modern apes and humans evolve initially?

Where did the ancestors of the modern apes and humans evolve initially?

Europe and then they migrated to Africa between 9-7 Ma.

When did the last common ancestor between chimps and the line that led to humans live?

Between 9.3-6.5 Ma.

• Date is debated

Sahelanthropus tchadensis

• Lived between 7.2-6.8 Ma. in Chad

• Had a forward foramen magnum

• May have been an ape ancestor because it is the earliest know knuckle-walking ape

Australopithecus afarensis

• Lived between 3.85-2.95 Ma. in Kenya, Tanzania, and Ethiopia

• The earliest undisputed bipedal hominid in 3.72 Ma.

  • Her name was Lucy

Homo habilis

• Lived between 2.644-1.44 Ma.

• Lived in Kenta, Tanzania, South Africa, had cranial features like hominids

Homo erectus

• Lived between 1.95 Ma.

• Found in Africa, Europe, Asia

Homo sapiens neandertalensis

• Lived between 400-40 Ka.

• The last common ancestor for Neanderthal and sapiens lived 750-550 Ka.

Homo bodoensis

• Originally classified as Middle Pleistocene hominins

• Lived between 774-129 Ka.

• Reclassified due to a specimen found in bodo D’ar, Ethiopia

What did Homo bodoensis eventually evolve into?

Homo sapiens in Africa and Neanderthal in Europe

Homo sapiens sapiens

• Species was evolved to this point around 286 +/- 32 Ka.

• Still exist today (duh)

• Fossils of five individuals were found in Morocco with tools

What are the 11 characteristics of human primates?

1. Largest brains relative to body weight (1:40, large cerebral cortex and more neural connections)

2. No muzzle due to cooking food

3. Capable of complex learning

4. Cultural responses as a central human adaptive strategy (fire, clothing, tools, weapons)

5. Advance use of symbolic communication (language)

6. Concealed ovulation in females (no estrus cycle)

7. Human infants are dependent on mothers much longer (gives them more time to mature)

8. Male-female division of labor

9. Hands are free to make/use tools

10. Food can be carried and transported back to base camp

11. Bipedal/ bipedal locomotion

Bipedal locomotion

• A controlled fall

  • One foot catches the body and pushes off the ground to keep walking

Cranium Characteristics

• Head balances atop of spinal column allows scanning motion

• Have binocular vision and can find objects even with camouflage concealing it

Spine Characteristics

• Human S-shaped spine; quadrupled spines are arched/bridge-shaped

• Human vertebrae are shorter/wider (provides more support)

Pelvis Characteristics

• Human pelvis is shorter and flatter

• Flared outward

• Gluteus maximus is largest muscle in humans

  • On back of pelvis

• Human g.m + hamstrings extend longer than femur

  • Allows for greater leverage for stride

Knee Characteristics

• Medial angle of femur to tibia is 90 degree in apes and 101 in humans

• Human center of gravity remains along centerline of body while walking

  • Apes shift side to side

Foot Characteristics

• Feet are weight bearing in humans

• Big toe (hallux) is enlarged and parallel to the other toes

• Humans have longitudinal arches on bottom of feet, apes have transverse arches

What was the H. sapiens ecological niche in Africa when just starting out?

Being a daytime hunter on the African savannah

• No one else hunted during the day besides the cheetah because the calories burned while doing and overheating so wasn’t worth it

Physical and behavioral characteristics in Ancestors of Great Apes and Contemporary Great Apes

• Small brains compared to modern humans

• Fur

• Quadruped/knuckle-walking

• Lived in jungle

Physical/behavioral characteristics in Australopithecines

• Small brains compared to genus Homo

• Fur at first but lost it around 3 Ma.

• Bipedal with remnants of arboreal skeletal adaptations

• Lived in savannah

Physical/Behavioral Characteristics of Homo

• Large brains

• Virtually hairless (except for pubes and top of head)

• Obligate terrestrial bipeds

Advantages to large brains and bipedalism

• Less surface area exposed to sun (only head and shoulders)

• Heat transfer from organism to atmosphere is faster because humans are hairless

• We have more sweat glands and can efficiently use evaporative cooling (10x number of sweat glands than chimps due to mutated 1-EN1 gene)

• Ability to run long distances in heat

Other human advantages

• Humans are social and can hunt in groups and share strategy super effectively/efficiently

  • Anticipates animal behavior, trap, track

Negative adaptations of humans

• We use up carbohydrates faster (glucose)

• Sodium loss is great

• Water lost (need 1.3 liters/day and can die when go 4 days without water)