Primate Evolution and Early Hominids

Primate Evolution

• Primates are mammals, including monkeys, apes, and humans.
• Oldest primate fossils date back 65 million years, following the extinction of dinosaurs.
• Key primate characteristics:
  • Opposable thumbs for grasping.
  • Relatively large brains (e.g., chimpanzee brain size ~300cc).
  • Omnivorous diet.
  • Stereoscopic vision and color vision for enhanced survival.
  • Rotatable forearms, single births, no tail (in humans).
• Humans and chimpanzees shared a last common ancestor approximately 7 million years ago.

Early Hominids

• Hominids are human-like animals that walked upright.
• Early hominids lived in humid forests of East and Southern Africa, transitioning to grasslands due to climate change.
• Hominid adaptations compared to chimpanzees:
  • Smaller jawbones.
  • Larger brain sizes.
  • Reduced brow ridges.
  • Smaller teeth.
• Australopithecus (Southern Ape) was the first primate to habitually walk on two legs, differing in walking mechanics from later hominids.
  • Sexual dimorphism (males larger than females).
  • Lucy (40% complete skeleton, East Africa, ~3.2 million years ago; 107cm tall) is a notable example.
• Tool use emerged approximately 2-3 million years ago, coinciding with a growth in brain size.

Walking Upright

• Walking upright (bipedalism) in early hominids offered advantages like freeing hands for tasks like carrying objects or infants.
• However, bipedalism presented challenges, requiring adaptations in the skeletal system.
  • A change in the location and shape of the skull, upper body, spine, hips, knees, and ankles.

Fire's Impact

• Fire use by hominids provided significant survival advantages:
  • Easier digestion of cooked food, potentially boosting brain development.
  • Illumination in low-light conditions.
  • Defense against predators.
  • Increased hunting efficiency in dark environments.
  • Maintaining body temperature. -Cooking meat provided easier digestion - increased nutrients led to larger brain sizes.

Tool Use and Cave Paintings

• Toolmaking developed, marking advancements in cognitive abilities.
• Cave paintings indicated further complexity in human societies and symbolic thought.

Agriculture

• The Younger Dryas event (a period of global cooling) led to the development of agriculture, providing a stable food supply, enabling human population growth.
• Agriculture marked a significant shift in human societies and led to lasting improvements in human survival.

Current Human Population

• The current global human population is approximately 8 billion.