Human Evolution A Brief Look at Where We

Human Evolution A Brief Look at Where We Came From

How Do We Know Evolution Has Occurred Clues to the past are left behind, for us to discover and interpret. �Fossils of bones, trace fossils, paintings, artifacts, DNA

Science Can Make Several Assumptions with Confidence �Africa is the birthplace of humanity �Modern humans evolved from apelike ancestors, through a series of intermediate steps �Human evolution has been varied, features evolving at different times, different rates

Some Key Transitions �About 7 -8 mya hominids diverged from the great apes, no fossil evidence this far back �About 4 mya bipedalism arose �About 2. 5 mya stone tools are being to be used �About 1. 5 mya more sophisticated tools are seen �About 0. 5 mya fire is mastered, spears �About 40, 000 ya symbols and signs of abstract thought (jewelry, paintings, burials) �About 10, 000 ya agriculture

Similarities Between Us and Chimpanzees �Shoulders with wide range of movement �Dexterous hands with fingers capable of grasping �Nails instead of claws �Relatively large brain �Cognitive abilities �Large complex social groups �DNA comparisons, 98% identical

Lineage Branching Term “hominid” refers to all species originating after human/African ape split

Bipedalism Arises ~4 mya

Why Bipedalism Arose �“Savanna” hypothesis-period of climate change �Upright posture allowed species to look over tall grasses. �Ability to carry food or young �Walk longer distances using less energy �Reach low branches �Less exposure to the hot African sun

Lucy ~3. 2 mya • This fossil was found in 1974, at the site of Hadar in Ethiopia. • About 40% of the hominid skeleton was discovered. • This skeleton is a member of A. afarensis • Skeleton is that of a full grown female, about 3. 5 ft. tall and 60 -65 pounds. • Bipedal, 1 st identified sp.

Laetoli Footprints Discovered in 1978, by Mary Leaky, in northern Tanzania. They are believed to footprints left by a member of A. afarensis (like Lucy). These footsteps are believed to be ~3. 6 myo. They indicate that 3 -4 individuals walked in the volcanic ash and left these prints. A “heel-strike” to “toe-off” gait, like humans, is found with these fossils.

Foramen Magnum Supporting Bipedalsim

Genus Homo �First appeared ~2. 5 mya �Gradual increase in brain size; ~400 - 500 cc to 1350 cc seen in modern humans �Advent of tool-making, this was advantageous due to climate changeallowed alternate food sources to be accessed

Dentition Also Changed Due to Diets

Homo habilis aka “tool man” �Lived between ~2. 5 - 1. 6 mya, at the same time as A. afarensis �Brain size increasing ~650 cc �Hands capable of tool making using stones to create simple blades

Homo erectus �Brain size ~900 cc �Made more sophisticated stone tools-”handaxes” �First species to leave Africa and spread throughout Asia and Europe �First to master fire

Homo neanderthalensis

�H. neanderthalensis lived about 250, 000 -30, 000 years ago �Mostly likely evolved from H. erectus species that had spread to Europe �Actually had a larger brain (1500 cc) than H. sapiens (1350 cc) �Had language �Produced sophisticated stone blades and spears �Adaptations for tolerating cold weather �Compact bodies that conserved heat �Protruding mid face �Low foreheads �Prominent brow ridges �Weak chins

H. Sapiens vs H. neanderthalensis

Homo sapiens �Anatomically modern humans, appearing about 200, 000 years ago �Much smaller brow ridge, high forehead, rounded braincase, prominent chin, flat face �Created tools that were more complex, often using new materials-bones and antlers �About 40, 000 years ago ornamentation appeared. This included jewelry, paintings, carvings, musical instruments �Evidence of “abstract” thought

�About 200, 000 modern humans originated in a small region in Africa from a population of H. erectus that had been isolated from the main population. The new species H. sapiens then migrated out of Africa into Asia and Europe.

�Previously thought that H. sapiens replaced H. neanderthalensis. �New evidence suggests that the two species actually interbreed. �Today’s humans have 1 -4% of neanderthal DNA in their genome. �This DNA is linked to Type 2 Diabetes, lupus, Crohn’s Disease, keratin � http: //humanorigins. si. edu/resources/intro-human-evolution

We have not changed much genetically over the last 30, 00040, 000 years but culturally we have changed significantly. What changes do you think we may experience in the future?