Human Evolution

Classification Hierarchy Kingdom Animal Phylum Chordate Class Mammal Order Primates Family Hominids Genus Homo Species Sapiens

Human Evolution

Important Vocabulary Paleoanthropologist Scientist who studies fossil evidence of human evolution. Homininds Group that includes humans and their immediate ancestors.

Background It is very rare to find a complete skeleton of a fossilized hominid. Scientists need to look at many different things to try and piece together the puzzle of human evolution.

Background Cont’d When hominid fossils are found, several important characteristics can help determine origin and lifestyle of the species. Did organism walk upright? Curvature of spine, position where spine attaches to skull and shape of pelvis Brain size? Examine skull fragments Diet? Wear and tear on fossilized teeth How and where did it live? Fossils found in same area & environment found

Primates 2 Divisions of Primates Characteristics: 1. Anthropoid primates 2. Prosimean primates Characteristics: Flat Nails (no claws) Prehensile hands and feet (grasping) Color vision and depth perception

Anthropoid Primates Include: Brain size Opposable thumbs marmosets Monkeys Apes Humans Brain size Large relative to their body size Opposable thumbs Similar dental formula number and arrangement of teeth

HUMANS Bipedalism – Ability to walk on 2 feet Aligned toes = Bipedalism Enlarged brain =Vertical face Areas for speech in the brain S- shaped spine Bowl-shaped pelvis

Prosimean primates Include: Lemurs Lorises Tarsiers

Tarsier Skeleton

Gorilla Skeleton

Human Skeleton

Hominids Hominids include humans and extinct humanlike primates The oldest known hominid fossils are between 6 and 7 million years old First fossils found in Africa

Australopithecus NOT ancestral to modern humans! Oldest known genus of hominids Lived more than 4 million years ago Knee joints- Allow bipedalism! Australopithecus anamensis Australopithecus afarensis – believed to have given rise to: A. africanus A. robustus A. boisei more than 1 million years ago NOT ancestral to modern humans!

A. africanus !

A. boiser !

Discovery of Lucy! Fossils of nearly half complete early hominid Australopithecus afarensis suggests hominids became bipedal before their brains began to dramatically enlarge

Ardipithecus ramidus Recent discovery Not clear whether it was bipedal 4.4 million years old

Existence of hominid species not ancestral to modern humans implies… Hominid phylogenetic tree is very branchy in appearance Representing species died out, leaving no descendants.

Early Members of the genus Homo H. habilis & H. erectus Ancestors to modern humans Larger brains than australopithecines May have had speech Started to develop tools Homo erectus Homo habilis

FIGURE 17-15 Representative hominid tools (a) Homo habilis produced only fairly crude chopping tools called hand axes, usually unchipped on one end to hold in the hand. (b) Homo ergaster manufactured much finer tools. The tools were typically sharp all the way around the stone; at least some of these blades were probably tied to spears rather than held in the hand. (c) Neanderthal tools were works of art, with extremely sharp edges made by flaking off tiny bits of stone. In comparing these weapons, note the progressive increase in the number of flakes taken off the blades and the corresponding decrease in flake size. Smaller, more numerous flakes produce a sharper blade and suggest more insight into toolmaking, more patience, finer control of hand movements, or perhaps all three.

Neanderthals For years, the thinking among anthropologists was that homo sapiens, being superior to Neanderthal man, ran him off the planet. More recently, that view has been discarded and the picture become more complicated. For one thing, Neanderthals may have mixed with the ancestor of modern man, which means that we could be carrying Neanderthal genes.

Cro-Magnons Cro-Magnons coexisted with Neanderthals in Europe and the Middle East for as many as 50,000 years Cro-Magnons had domed heads, smooth brows, and prominent chins 30,000-year-old Cro-Magnon artifacts include: Bone flutes Ivory sculptures Evidence of elaborate burial ceremonies

Cro-Magnon Cave Painting

Homo sapiens Evolved about 800,000 years ago A) Neanderthals Were early Homo sapiens They may be ancestral to modern humans OR They may have died out and been replaced by modern humans

Some hypotheses: 1. some anthropologist think H. sapiens evolved in PARALLEL from populations of H. erectus all over the world. (interbreeding) 2. some anthropologists propose that H. sapiens DESCENDED from H. erectus in Africa and then dispersed across Earth.

Waves of Hominid Emigration Two hypotheses have been proposed for the evolution of Homo sapiens “African replacement” hypothesis Also called Out of Africa, Recent-African-Origin “Multiregional origin” hypothesis

“African Replacement” Hypothesis Members of the genus Homo made repeated long-distance migrations out of Africa beginning 1.8 million years ago H. sapiens emerged from Africa about 150,000 years ago and spread across the Near East, Europe, and Asia The dispersing H. sapiens populations replaced all other hominids

FIGURE 17-18a Competing hypotheses for the evolution of Homo sapiens (a) The "African replacement" hypothesis suggests that H. sapiens evolved in Africa, then migrated throughout the Near East, Europe, and Asia, displacing the other hominid species that were present in those regions.

“Multiregional Origin” Hypothesis H. erectus emerged from Africa 1.8 million years ago and spread across the Near East, Europe, and Asia Continued migrations and interbreeding occurred among widespread H. erectus populations Regional populations of H. erectus evolved into H. sapiens

FIGURE 17-18b Competing hypotheses for the evolution of Homo sapiens (b) The "multiregional" hypothesis suggests that populations of H. sapiens evolved in many regions simultaneously from the already widespread populations of H. erectus.