Human Evolution and PREHISTORY

Human Evolution andPREHISTORY PART III: EVOLUTION OF THE GENUS HOMO AND THE DEVELOPMENT OF EARLY HUMAN CULTURE

Human Evolution andPREHISTORY Chapter Seven: HOMO HABILIS AND CULTURAL ORIGINS Link to the Canadian Association for Physical Anthropology

Chapter Preview When, Where, And How Did Human Culture Develop? When Did Reorganization And Expansion Of The Human Brain Begin? Why Did The Eating Of More Meat Lead To Improved Brains?

EARLY REPRESENTATIVES OF THE GENUS HOMO Olduvai Homo habilis, 1.8 my • 650-690 cc cranial capacity • Modern-looking hands, feet • Little difference from Australopithecus in body size, sexual dimorphism, and tree-climbing abilities • Maturation rate closer to apes • Associated with stone tools

Olduvai Homo habilis, 1.8 my OH 24

EARLY REPRESENTATIVES OF THE GENUS HOMO KNM ER 1470, Lake Turkana, 1.9 my • 752 cc cranial capacity • Cranium is more modern in appearance than in Australopithecus • Associated with stone tools

KNM ER 1470 1470

EARLY REPRESENTATIVES OF THE GENUS HOMO KNM ER 1470, Lake Turkana, 1.9 my • Inside of the skull shows a pattern in the left cerebral hemisphere that is associated with the speech area and right hand control of living humans • Wear patterns on tools indicate predominance of right-handedness • Brain was reorganized along human lines

Relations between Homo habilis and Australopithecus There is no agreement on what distinguishes Australopithecus from Homo One approach is to use the following characteristics: • Absolute brain size greater than 600 cc • Use of language and tools • Precision grip distinct to Homo

Relations between Homo habilis and Australopithecus Collard and Wood would define Homo by its adaptive zone Australopithecus • Body mass and shape more suited to closed environments, e.g. forest • Ape-like diet • Ape-like development pattern • Combined locomotion of bipedalism and climbing

Relations between Homo habilis and Australopithecus Collard and Wood would define Homo by its adaptive zone Homo • Body mass and shape more like ours, suited to open habitats • Diet more like ours • human-like development pattern • bipedalism

Relations between Homo habilis and Australopithecus • Marked increase in brain/body size ratio • Heat-exchange system to keep brain cool (only a rudimentary one in late gracile Australopithecines) • Smaller teeth in relation to skull size • Major brain-size increase and tooth-size reduction are important trends in the evolution of the genus Homo • Earliest fossils to exhibit these features appear by 2.4 mya (Baringo)

Relations between Homo habilis and Australopithecus • None of the robust Australopithecines belong in the direct human lineage; they coexisted with Homo habilis from 2.5 to 1 mya, headed in two very different evolutionary directions • The body of Homo habilis had changed little from gracile Australopithecines; hence, they are likely suitable ancestors for Homo • Did Australopithecus afarensis or Australopithecus africanus give rise to Homo habilis? • Or was it Kenyanthropus (Chapter 6), to the exclusion of all Australopithecines (minority view)?

Relations between Homo habilis and Australopithecus • Most see early East African graciles as generalized enough to have given rise to both Homo habilis and robust Australopithecus • Homo habilis and robust australopithecines appear about the same time in the fossil record • At least a 3-way split was underway by 2.5 mya (see Figures 7.5 and 7.6 on next slides and in text)

Relations between Homo habilis and Australopithecus

LOWER PALEOLITHIC TOOLS The beginning of the “Old Stone Age” is marked by the appearance of tools 2.6 million years old

Olduvai Gorge • 2 million years ago Olduvai was a lake, whose shores were inhabited by robust Australopithecines, Homo habilis and later Homo erectus (chapter 8) • Assemblages of stone tools (2 mya) were found, associated with bones of now-extinct animals and with evidence of butchering • On an occupation surface, 1.8 mya, there was a “stockpile” of basalt stones, forming a circle

Oldowan Tool Tradition • Flakes were struck from a stone either by using a hammerstone, or by striking the stone against a large rock (anvil), using thedirect percussion method • It produced tools with sharp edges, effective for cutting and scraping • Microscopic wear patterns show tool use for cutting meat, grasses, wood

Oldowan Tools • Important technological advance for early hominins • Saving of labour and time • Addition of meat to diet on afrequent basis • Since dentition of Australopithecus and Homo is poorly suited for meat eating (e.g. small canines), sharp tools for butchering were needed

Tool Use • Probably a result ofadaptationto an environment changing from forests to grasslands, 3-2 mya (see Figure 6.11)

Oldowan Tools and Bone Assemblages • H. habilis and large carnivores were active at the same locations, based on combinations of toolmarks and gnaw marks • Whole carcasses of animal skeletons are not represented • Tools were made of materials that were procured at a distance • There was repeated use of sites over periods of 5-15 years Suggesting that our Oldowan forebears were SCAVENGERS

Tools, Meat, and Brains • After 2.5 mya meat became an important part of the hominin diet • Early hominins lacked size and strength to compete for kills and to drive off predators, so must have relied on wit and cunning

ORIGINAL STUDY Cat in the Human Cradle • An anatomical analysis has suggested that both Homo habilis and A. afarensisi were better than us at climbing trees and suspending • Archaeological evidence from South Africa and observation of modern-day leopard activity support “tree-caching” as an ancient form of leopard behaviour in Africa • The collection of bones at Olduvai Gorge then could be explained by both ground scavenging and the scavenging of leopard “tree kills” by Homo habilis

“Man the Hunter” • In the 1960s and 1970s the “man the hunter” model for provisioning of the social group was supported, followed later by documenting the role of “woman the gatherer” • Cooperation in food procurement and division of labour by sex are seen as prime factors in the success of early Homo in this model • Since these factors relate to male-female differences in thedistant past, they are generally attributed to biologically determined sex differences rather than gender

Tools, Meat, and Brains • Behavioural reconstructions from fragments of bone and stone rely on observations of living primates, human (e.g. modern food foragers) and nonhuman • It is likely that the culture of Homo habilis played a role in food-sharing behaviours, rather than strict biological male-female differences

Hominid Brain and Meat Consumption • Increase in brain size correlates with appearance of meat in the hominin diet • The human brain consumes more than twice the energy of the brains of nonhuman primates • Meat is more energy-dense than plant food, important for the evolving brain

Daniel Wolpert...The Real Reason for Brains • “You may reason that we have brains to perceive the world or to think, and that’s completely wrong.”

Hominid Brain and Meat Consumption • The most readily accessible plant sources were leaves and legumes, difficult for primates to digest • Chimps search for animal foods on the savanna; why not our ancestors, too? • Increased meat consumption ensured an adequate intake of essential amino acids and more leisure time for exploring the environment • These factors may have stimulated brain development, as indicated by significant increase in brain size in Homo habilis

THE EARLIEST SIGNS OF CULTURE AND TOOLS • Problem solving, e.g. the use of stone tools to butcher and prepare meat • Tool manufacture, emphasizing manual dexterity and fine manipulation, resulting in improved organization of the nervous system • Abstract idea of the tool, plus the steps and materials to make it

Language Origins • Importance of cooperation, planning and foresight for H. habilis raises questions about communication abilities • Humans and apes share a gesture-call system, inherited from the common ancestor • Humans and apes share language potential (apes to the level of a 2-3 year-old) • These sharedabilities must have been possessed by the earliest hominins as well

Language and the Homo habilis Brain • The speech area is adjacent to that involved in precise hand control • Manufacture of Oldowan tools require manual skills beyond those of chimpanzees using stones and anvils for nut-cracking (chapter 4) • H. habilis exhibited handedness in toolmaking which is associate with lateralization of the brain • Lateralization is associated with language

Wernicke’s area and Broca’s area are two areas in the brain associated with speech. Both are believed to have been present in the Homo Habilis brain.

NEXT TIME: Homo erectus and the Emergence of Hunting and Gathering

Human Evolution and PREHISTORY