Chapter 11 Primates and Human Evolution Primate Characters

Chapter 11 Primates and Human Evolution

Primate Characters • Grasping hands and feet with thumb and big toe often opposable • Sensitive pads on fingertips and nails instead of claws • A mobile shoulder joint, especially in humans • Large braincase and a postorbital bar • Flattened face with eyes rotated forward for stereoscopic vision • Usually have one offspring at a time • Females have only two mammary glands

Anthropoid Origins • Anthropoid (“human-like”) primates were thought to have originated in Africa. • Recent finds from the early Eocene of China and Thailand (above) have challenged this view because they are older. • Anthropoids are distinct in having rounded nostrils (not slit-like as in prosimians), usually large canines, molar-like premolars, and broad square molars.

Miocene Apes • Proconsul is the bestknown early ape, early Miocene of Kenya. Proconsul • Proconsul is designed for diverse locomotion styles (quadrupedal running, standing upright, swinging from branches) and could probably swing a stick for defense.

Hominoid Relationships Hominidae – great apes Hylobatidae – lesser apes Pongidae (ape family) has been eliminated as a paraphyletic group, and Hominidae (human family) has been expanded to include most apes. Note in the right diagram that no common ancestors are known!

Classification of Apes and Humans Superfamily Hominoidea • Family Hylobatidae – gibbons – Smaller tree-climbing apes • Family Hominidae – Subfamily Ponginae – Orang-utans • Slow climbers and brachiators – Subfamily Homininae • Terrestrial quadrupeds – chimps and gorillas • Infrafamily Hominini – Terrestrial bipeds – humans – Monophyletic group of humans and their closest relatives

Apes • Apes arose in the Miocene of Africa as grasslands developed there, have short 5‑cusp molars Baboon • Early-middle Miocene: Dryomorphs – Large canines, Africa to Eurasia • Middle-late Miocene: Ramapithecines Chimp – Small canines, very diverse, Africa to Asia • Pliocene: poor fossil record leaves many questions about hominid relationships, including the origins of living groups of apes

Apes • It was long believed that Ramapithecus was the first human and that the human/ape split occurred 15 M. Y. ago. DNA and protein similarities, however, suggested a mere 5 M. Y. ago split, with man, chimp, and gorilla being equally similar. Discovery of more skeletal material suggested that Ramapithecus is an orang-utan. • Gorillas and chimps have no definite fossil record, so tracing their ancestry is difficult.

Late Miocene Apes Sivapithecus (=Ramapithecus) of China region Modern human Chimp Jaw and molars of Sivapithecus showing “Y” and cusp pattern Hand of Dryopithecus Lower jaw of Gigantopithecus (late Miocene of India and Pleistocene of China)

Humans and Upright Posture Grasping hand Gorilla Loss of opposable toe in foot Foot flat with straight toes for plantigrade walking Walking on knuckles

Modifications for Bipedalism • Skull with ventral foramen magnum • Backbone develops an S-curve • Pelvis short with bowl-shaped ilium to support abdominal organs • Hip joint faces downward and sideways • Long, slender leg bones • Knee forms a straight hinge for standing • Foot a flat platform with non-opposable toes

Reasons for Bipedalism • Ability to stand tall for a better view • Freeing up the hands to use tools • Faster or more efficient locomotion • One theory is that forest-dwelling apes became restricted to west Africa where they gave rise to chimps and gorillas, while humans arose as an adaption to the open grasslands in east Africa.

Brain First Theory • The early popular theory was that the big brain was required for tool use, so it came before bipedalism. • This was confirmed by a skull at Piltdown, England, with a large braincase but primitive jaws (a). • Piltdown man turned out to be a hoax (a human cranium planted with an orang-utan jaw). • Australopithicus found in Africa (b) disproved the brain first theory with its small brain and bipedalism.

Piltdown Man • Discovered 1912 near Piltdown, East Sussex, England • Exposed as a fraud in 1953 • Parts of human skull and orangutan jaw etched with acid and buried at an excavation site. Why was the hoax so readily accepted by England’s experts?

Piltdown Man Most human fossils had been found in Africa. There were racist views about Africa. It was a relief to find evidence of human evolution in Europe. Though the skull was from a modern human, Piltdown was considered intermediate in brain size between Homo erectus and Neanderthal Man!

Adult Chimp Adult Human Juvenile Chimp Juvenile Human Neoteny is the evolutionary process where juvenile traits are retained into adulthood. Human evolution may be a case of neoteny. Enlargement of the human brain could have been accomplished by retaining the juvenile proportions of an ape. This could also explain the loss of hair in humans. But it fails to explain our large legs.

Early Human Fossils • Orrorin – teeth, jaw fragments, broken limb bones that suggest bipedalism, 6 M. Y. old • Sahelanthropus – distorted cranium (at right) with foramen magnum that suggests bipedalism, 6 M. Y. old • Ardipithecus – teeth, skull fragments, and limb bones from several individuals with somewhat large canines, thin tooth enamel, and clear evidence of bipedalism, 5. 8 to 4. 4 M. Y. old • Praeanthropus – Lucy (most of skeleton found in 1974) and other bones and teeth, 4. 1 to 2. 9 M. Y. old

Praeanthropus walked fully upright Early hominids had the distinct human pelvis for upright walking. Fossil trackways also demonstrate full bipedality.

Evolution of Human Characters Chimp Ardipithecus Praeanthropus Palate of Lucy Ape Legs Skeleton of Lucy (Praeanthropus), the most complete early hominid skeleton Modern human Fingers Ape Praeanthropus Modern human

Australopiths • All previously included in genus Australopithecus • Praeanthropus – small primitive forms such as Lucy (P. afarensis) with strong sexual dimorphism • Australopithecus – advanced gracile australopiths that probably gave rise to Homo • Paranthropus – robust australopiths with broad faces and massive jaws (at right) • The last two have small canines and no diastema

Human Timeline

Later Australopiths • Australopithecus africanus (gracile, 3. 0 -2. 3 M. Y. ago) • Paranthropus robustus (robust, 1. 9 -1. 6 M. Y. ago) • Paranthropus boisei (robust, 2. 4 -1. 3 M. Y. old)

Human Relationships

Hominid Species Hominid species Praeanthropus afarensis Age Brain size Height 4. 0‑ 3. 0 M. Y. 380‑ 450 cc 1. 2 m Australopithecus africanus 3. 0‑ 2. 3 M. Y. 380‑ 450 cc 1. 4 m Paranthropus robustus 1. 9‑ 1. 6 M. Y. 380‑ 450 cc 1. 5 m Paranthropus boisei 2. 2‑ 1. 2 M. Y. 380‑ 450 cc 1. 5 m Homo habilis 2. 0‑ 1. 6 M. Y. 630‑ 700 cc 1. 3 m Homo erectus 1. 6‑ 0. 3 M. Y. 800‑ 1300 cc 1. 7 m Homo sapiens 0. 1‑ 0. 0 M. Y. 1000‑ 2000 cc 1. 8 m - Neanderthal Man (replaced Homo erectus, large brow ridges, elaborate burials) - Cro‑Magnon Man (replaced Neanderthal 40, 000 yr, made cave art in France/Spain) - Modern Man (developed from earlier forms, domesticated plants and animals)

Early Species of Homo • Homo habilis (“handy man”) was discovered in Olduvai Gorge, Kenya, in the 1960 s by Louis Leakey and has a much larger brain than the australopiths. • Homo rudolfensis is a possible second species from Kenya with a larger brain but other more primitive features (skull above). • Without the enlarged brain both would better be classified as australopiths. Both are 2. 4 -1. 5 M. Y old.

Earliest Homo (Africa) • Homo habilis and Homo rudolfensis represent one or two species of early Homo from Kenya. • Homo probably evolved from the Australopithecus africanus. Homo habilis • The primary feature is a large increase in cranial size over Australopithecus. • Homo coexisted with robust Australopithecus for about a million years.

Homo erectus – Exiting Africa Prior to 2 million years ago humans were restricted to eastern Africa. • The earliest Homo erectus (or H. ergaster) (a) dates to 1. 9 M. Y. ago and has a brain size of 830 cm 3 but retains heavy jaws and brow and lacks a chin. • More specialized Homo erectus material is found throughout Eurasia dating 1. 9 -0. 5 M. Y. ago along with Acheulean hand axes (b-d).

Evolution of Homo Peking Man Neanderthal Man (Homo erectus) Common in Africa and Asia (Homo sapiens neanderthalensis) Common in Africa and Europe

Stone Tools Neanderthal (Homo sapiens) Homo erectus Homo habilis

Neanderthal Man • Neanderthal Man (a, c) is an archaic form of Homo sapiens that branched off half a million years ago and lived till 30, 000 years ago. • Compared to modern man (b) they had a similar brain size but differences in head shape. Invading Cro Magnon may have killed them.

Modern Man • Found in Africa and Israel dating back 100, 000120, 000 years ago (skull above) • Spread into Europe 40, 000 years ago (Cro. Magnon Man), but no evidence they mixed with Neanderthals, and to Australia at the same time • DNA evidence shows that the latest common ancestor of all living humans lived about 200, 000 years ago in Africa (“Mitochondrial Eve”).

Dispersal of Modern Humans The Americas were the last continents to be colonized, with the oldest well-documented site in Chile! The Ice-Age Bering Land Bridge is the obvious route, but there’s debate whether they traveled inland (big game hunters) or along the coast (fishermen).

Humans arrived in the Americas about 14, 000 years ago. • The old theory is that humans traveled between the ice sheets of Canada in what is called the “ice-free corridor. ” • An newer theory is that they came down the Pacific Coast by boat (supported by Dr. Heaton’s Alaska research).

LGM Ice Cover

Cast of human mandible in On Your Knees Cave (9, 800 yr B. P. ) By Erik Hill, Anchorage Daily News

Archaeological Excavation at On Your Knees Cave Many bifaces, microblades, bone tools, and cultural charcoal beds were found inside and outside the cave.

Common mammals from On Your Knees Cave Middle Wisconsin 50, 000 -24, 000 yr B. P. Brown bear Black bear Arctic fox River otter Harbor seal Steller’s sea lion Caribou Saiga (or goat) Long-tailed vole Hoary marmot > Heather vole > Brown lemming > Last Glacial Maximum 24, 000 -13, 000 yr. B. P. Arctic fox Red fox Ringed seal Harbor seal Steller’s sea lion Maybe Brown bear Black bear Otter/Mink Caribou Postglacial 13, 000 yr B. P. -present Brown bear Black bear Arctic fox Red fox River otter Steller’s sea lion Caribou Black-tailed deer Long-tailed vole Human Bold indicates index species

The Northwest Coast • The coast had more exposed land area during the Last Glacial Maximum than previously thought. • The period of maximum ice cover was very brief. • The coast provided an easy means of transportation • The coast had a more moderated climate then the interior. • The coast had a rich supply of seafood. • Making a living along the coast required similar culture at all latitudes, whereas traversing the interior requires diverse adaptations. • This could explain the rapid colonization of North and South America.