How Did Humans Evolve? Some Early Primate Adaptations for Life in Trees Were Inherited by Humans The Oldest Hominid Fossils Are from Africa The Earliest Australopithecines Could Stand and Walk Upright Several Species of Australopithecus Emerged in Africa The Genus Homo Diverged from the Australopithecines 2.5 Million Years Ago

The Evolution of Homo Was Accompanied by Advances in Tool Technology Neanderthals Had Large Brains and Excellent Tools Modern Humans Emerged Only 150,000 Years Ago Several Waves of Hominids Emigrated from Africa

The Evolutionary Origin of Large Brains May Be Related to Meat Consumption The Evolutionary Origin of Human Behavior Is Highly Speculative The Cultural Evolution of Humans Now Far Outpaces Biological Evolution

Primates Primates include tarsiers, lemurs, monkeys, apes, and humans Figure 17-12, p. 332 illustrates representative primates…

Figure: 17-12 Title: Representative primates Caption: The (a) tarsier, (b) lemur, and (c) lion-tail macaque monkey all have relatively flat faces, with forward-looking eyes providing binocular vision. All also have color vision and grasping hands. These features, retained from the earliest primates, are shared by humans.

Figure: 17-12 part a Title: Representative primates part a Caption: The (a) tarsier, (b) lemur, and (c) lion-tail macaque monkey all have relatively flat faces, with forward-looking eyes providing binocular vision. All also have color vision and grasping hands. These features, retained from the earliest primates, are shared by humans.

Figure: 17-12 part b Title: Representative primates part b Caption: The (a) tarsier, (b) lemur, and (c) lion-tail macaque monkey all have relatively flat faces, with forward-looking eyes providing binocular vision. All also have color vision and grasping hands. These features, retained from the earliest primates, are shared by humans.

Figure: 17-12 part c Title: Representative primates part c Caption: The (a) tarsier, (b) lemur, and (c) lion-tail macaque monkey all have relatively flat faces, with forward-looking eyes providing binocular vision. All also have color vision and grasping hands. These features, retained from the earliest primates, are shared by humans.

Early Primates Were Adapted for Life in Trees Some of these adaptations were inherited by humans Large, forward-facing eyes with overlapping fields of view (allowed accurate depth perception) Color vision Grasping hands Enlarged brain (facilitated hand-eye coordination and complex social interactions)

The Oldest Hominid Fossils Are from Africa Hominids include humans and extinct humanlike primates The oldest known hominid fossils are between 6 and 7 million years old

The Oldest Hominid Fossils Are from Africa Sahelanthropus tchadensis lived more than 6 million years ago Exhibits human-like and ape-like characteristics See Figure 17-13, p. 333…

Figure: 17-13 Title: The earliest hominid Caption: This nearly complete skull of Sahelanthropus tchadensis, which is more than 6 million years old, is the oldest hominid fossil yet found.

The Oldest Hominid Fossils Are from Africa Ardipithecus ramidus and Orrorin tugenensis lived between 4 million and 6 million years ago Knowledge of these earliest hominids is limited - few specimens have been found

The Oldest Hominid Fossils Are from Africa The first well-known hominid line, the australopithecines, arose about 4 million years ago See Figure 17-14, p. 334…

Figure: 17-14 Title: A possible evolutionary tree for humans Caption: This hypothetical family tree shows facial reconstructions of representative specimens. Although many paleontologists consider this to the most likely human family tree, there are several alternative interpretations of the known hominid fossils. Fossils of the earliest hominids are scarce and fragmentary, so the evolutionary relationship of these species to later hominids remains unknown.

The Australopithecines The earliest australopithecines possessed knee joints that permitted bipedal (upright, two-legged) locomotion 4 million year old fossilized footprints confirm that early australopithecines sometimes walked upright

The Australopithecines An upright stance was significant in the evolution of hominids because it freed their hands from use in walking

The Australopithecines Several species of Australopithecus have been identified from fossils Australopithecus anamensis Australopithecus afarensis – believed to have given rise to: A. africanus A. robustus A. boisei All australopithecines were extinct by 1.2 million years ago

The Genus Homo The genus Homo diverged from the australopithecine line 2.5 million years ago See Figure 17-14, p. 334 for a possible evolutionary tree for humans…

Figure: 17-14 Title: A possible evolutionary tree for humans Caption: This hypothetical family tree shows facial reconstructions of representative specimens. Although many paleontologists consider this to the most likely human family tree, there are several alternative interpretations of the known hominid fossils. Fossils of the earliest hominids are scarce and fragmentary, so the evolutionary relationship of these species to later hominids remains unknown.

The Genus Homo Homo habilis appeared 2.5 million years ago Bodies and brains were larger than australopithicenes Retained apelike long arms and short legs

The Genus Homo Homo ergaster appeared 2 million years ago Limb proportions were more like those of modern humans

The Genus Homo Homo ergaster is believed by many to be the common ancestor of: H. erectus (first hominid species to leave Africa approximately 1.8 million years ago) H. heidelbergensis Some migrated to Europe and gave rise to H. neanderthalensis Those remaining in Africa gave rise to H. sapiens (modern man)

Advances in Tool Technology Hominid evolution is closely tied to the development of tools Homo habilis produced fairly crude chopping tools that were unchipped on one end to hold in the hand See Figure 17-15(a), p. 336 to observe an example of a hand axe…

Homo habilis Copyright © 2005 Pearson Prentice Hall, Inc. Figure: 17-15 part a Title: Representative hominid tools part a Homo habilis Caption: (a) Homo habilis produced only fairly crude chopping tools called hand axes, usually unchipped on one end to hold in the hand. Copyright © 2005 Pearson Prentice Hall, Inc.

Advances in Tool Technology Homo ergaster produced finer tools that were typically sharp all the way around the stone Some of these may have been tied to spears See Figure 17-15(b), p. 336 to observe examples of H. ergaster tools…

Homo ergaster Figure: 17-15 part b Title: Representative hominid tools part b Homo ergaster Caption: (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.

Advances in Tool Technology Homo neanderthalensis produced exceptionally fine tools with extremely sharp edges made by flaking off tiny bits of stone See Figure 17-15(c), p. 336 to observe examples of H. neanderthalensis tools…

Homo neanderthalensis Figure: 17-15 part c Title: Representative hominid tools part c Homo Neanderthal Caption: (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 either more insight into tool making, more patience, finer control of hand movements, or perhaps all three.

The Neanderthals Neanderthals lived in Europe from 150,000 to 30,000 years ago They were heavily muscled, had brains slightly larger than modern humans, walked fully erect, and constructed finely crafted stone tools

The Neanderthals Neanderthals were once believed to be a variety of H. sapiens; however, molecular evidence indicates that Neanderthals are a separate species

Modern Humans Homo sapiens appeared in Africa about 150,000 years ago European and Middle Eastern H. sapiens appeared about 90,000 years ago and were known as Cro-Magnons

Cro-Magnons 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 See Figure 17-16, p. 337…

Figure: 17-16 Title: Paleolithic burial Caption: This 24,000-year-old grave shows evidence that Cro-Magnon people ritualistically buried their dead. The body was covered with a dye known as red ocher, then buried wearing a headdress made of snail shells and with a flint tool in its hand.

Cro-Magnons Unlike their predecessors, Cro-Magnons created remarkable cave paintings that made use of sophisticated artistic techniques See Figure 17-17, p. 337…

Figure: 17-17 Title: The art of Cro-Magnon people Caption: Cave paintings by Cro-Magnons have been remarkably preserved by the relatively constant underground conditions of a cave in Lascaux, France.

Cro-Magnons and Neanderthals Lived Side by Side Cro-Magnons coexisted with Neanderthals in Europe and the Middle East for as many as 50,000 years It is not known why the Neanderthals became extinct

Several Waves of Hominids Emigrated from Africa Two hypotheses have been proposed for the evolution of Homo sapiens “African replacement” hypothesis “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

“African Replacement” Hypothesis The dispersing H. sapiens populations replaced all other hominids See Figure 17-18(a), p. 339…

African Replacement Hypothesis The spread of Homo erectus began at least 1.8 million years ago Homo sapiens' expansion began around 100,000 years ago Figure: 17-18 part a Title: Competing hypotheses for the evolution of Homo sapiens part a Caption: (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

“Multiregional Origin” Hypothesis Regional populations of H. erectus evolved into H. sapiens See Figure 17-18(b), p. 339…

Multiregional Hypothesis Regional populations of Homo erectus evolved into Homo sapiens while intermingling with one another Figure: 17-18 part b Title: Competing hypotheses for the evolution of Homo sapiens part b Caption: (b) The "multiregional" hypothesis suggests that populations of H. sapiens evolved in many regions simultaneously from the already widespread populations of H. erectus. Question Paleontologists recently discovered fossil hominids with features characteristic of modern humans in 160,000-year-old sediments in Africa. Which hypothesis does this new evidence support?

The Evolutionary Origin of Large Brains Highly developed brains may have evolved in response to increasingly complex social interactions, such as the cooperative hunting of large game

The Evolutionary Origin of Large Brains If the distribution of this group-hunted meat was best accomplished by individuals with large brains, then natural selection may have favored such individuals

The Cultural Evolution of Humans Human evolution has come to be dominated by cultural evolution, the transmission of learned behaviors from generation to generation

The Cultural Evolution of Humans The evolutionary success of humans is the result of cultural evolution and a series of technological revolutions The development of tools The agricultural revolution The industrial revolution

The Cultural Evolution of Humans Human cultural evolution and the accompanying increases in human population have resulted in humans becoming an important agent of natural selection with respect to other life forms

The Cultural Evolution of Humans In the words of Stephen Jay Gould, “We may not be suited for our role as stewards of life’s continuity on Earth, but here we are”