Human Evolution

Evolution: Gradual change in living organisms over generations. Results in formation of new species.

Evidence: (1) Fossil records, (2) Comparative anatomy, (3) Embryology, (4) Vestigial organs, (5) Biochemical similarities.

Theories: (1) Lamarckism (inheritance of acquired characters), (2) Darwinism (natural selection), (3) Modern synthetic theory.

Human Evolution: Study of how humans evolved from primate ancestors.

Hominids: Family of primates including humans and extinct ancestors.

Diagram Importance: Timeline of human evolution showing different species is essential.

Lamarck's Theory: Organisms acquire characters during lifetime, pass to offspring. Example: Giraffe neck elongation.

Criticism: Not supported by experiments. Acquired characters not inherited.

Darwin's Theory: (1) Overproduction, (2) Struggle for existence, (3) Variations, (4) Survival of fittest, (5) Natural selection.

Natural Selection: Nature selects organisms best adapted to environment for survival and reproduction.

Modern Synthetic Theory: Combines Darwinism with genetics. Variations due to mutations, recombination, genetic drift.

Evidence for Darwinism: (1) Fossil records, (2) Geographical distribution, (3) Comparative embryology, (4) Vestigial organs.

Dryopithecus: Forest-dwelling ape. Lived 15-20 million years ago. Walked on all fours.

Ramapithecus: Lived 12-14 million years ago. Possible early human ancestor. Ate soft fruits and leaves.

Australopithecus: Lived 2-5 million years ago. Walked upright. Brain size: 400-500 cc.

Homo habilis: 'Handy man'. Lived 2 million years ago. Used tools. Brain size: 650-800 cc.

Homo erectus: 'Upright man'. Lived 1.5 million years ago. Used fire. Brain size: 900 cc.

Homo sapiens neanderthalensis: Neanderthals. Lived 100,000-40,000 years ago. Robust build, large brain.

Homo sapiens sapiens: Modern humans. Evolved 50,000 years ago in Africa.

Diagram Importance: Comparative skulls of different hominids showing evolution is crucial.

Bipedal Locomotion: Walking on two legs. Freed hands for tool use.

Brain Development: Increased brain size from 400 cc to 1400 cc. Allowed complex thinking.

Jaw and Teeth: Reduced jaw size, smaller teeth. Diet changed from raw to cooked food.

Forehead and Chin: Prominent forehead, well-developed chin in modern humans.

Cultural Evolution: Development of language, art, technology.

Migration: Humans migrated from Africa to other continents.

Fossils: Remains or traces of ancient organisms preserved in rocks.

Types: (1) Petrified fossils, (2) Molds and casts, (3) Carbon films, (4) Trace fossils.

Fossil Sites: (1) Siwalik hills (India), (2) Olduvai Gorge (Africa), (3) Zhoukoudian (China).

Dating Methods: (1) Relative dating (stratigraphy), (2) Absolute dating (carbon dating, potassium-argon).

Carbon Dating: Measures radioactive carbon-14 decay. Used for fossils up to 50,000 years old.

Importance: Fossils provide evidence of evolutionary relationships.

Vestigial Organs: Reduced, non-functional structures inherited from ancestors.

Examples: (1) Appendix - remnant of large cecum in herbivores, (2) Wisdom teeth - no space in modern jaw, (3) Tailbone (coccyx) - remnant of tail, (4) Body hair - reduced in humans, (5) Ear muscles - cannot move ears.

Significance: Evidence of evolution. Shows humans evolved from ancestors with different lifestyles.

Homologous Organs: Similar structure, different function. Example: Human arm, dog forelimb, whale flipper.

Analogous Organs: Different structure, same function. Example: Bird wing, insect wing, bat wing.

Comparative Embryology: Embryos of different vertebrates show similarities. Example: Gill slits in human embryos.

Biochemical Evidence: Similar DNA, proteins, blood groups across species indicate common ancestry.

Timeline: (1) 15-20 mya: Dryopithecus, (2) 12-14 mya: Ramapithecus, (3) 2-5 mya: Australopithecus, (4) 2 mya: Homo habilis, (5) 1.5 mya: Homo erectus, (6) 100,000 ya: Neanderthals, (7) 50,000 ya: Modern humans.

Out of Africa Theory: Modern humans originated in Africa and migrated to other continents.

Cro-Magnon Man: Early modern humans. Lived 40,000 years ago. Made cave paintings.

Neanderthal Extinction: Disappeared 30,000 years ago. Possibly due to competition with modern humans.