Chapter 2 – Human Origins: 7 Million to 1.9 Million Years Ago

Chapter Overview

The chapter begins with a description of the Pleistocene epoch, which is also known as the Great Ice Age or the Ice Age. The Pleistocene epoch lasted from 1.6 mya to about 15,000 years ago. During the Pleistocene, the climate shifted from glaciated periods to interglaciers (times when the climate was warmer than today’s climate). The shift from warm to cold climates caused changes in the regional distribution of plants and animals. Deep-sea cores offer information about the climate changes during the Pleistocene. Climate fluctuations, believed to be caused by astronomical changes, are apparent roughly every 100,000 years for the past 800,000 years.

Primates include two suborders: anthropoids (apes, monkeys, and humans) and prosimians (lemurs, tarsiers, and “premonkeys”). Research in the past century has shown that there are similarities in the behavior and physical characteristics of hominids and pongids. Aegyptopithecus was an Oligocene (35 to 30 mya) fruit-eating primate that was no larger than a fox and weighed no more than 4 to 4.5 kg (9 to 10 pounds). The Fayyum Depression west of the Nile contains fossil remains of Aegyptopithecus. The oldest African ape ever to have been discovered lived during the Miocene epoch (26 to 16 mya). Proconsul is the best known Miocene ape. They were quadrupedal and arboreal. Between 15 and 12 mya, apes that relied on soft foods became extinct and were replaced by those who could eat harder fruit, grass, and seeds, such as Kenyapithecus, who had large molars, flourished in eastern Africa, and was quadrupedal. The archaeological record between 11 to 5 mya is sparse and the transitional form has not been found. David Pilbeam has suggested that the transitional forms were likely arboreal with long arms and legs and a broad chest. The hominid adaptation to bipedality likely incurred an advantage to spending more time feeding on the ground, providing more endurance for walking long distances, and could potentially have had social advantages.

Advances in molecular biology have lead to insights into human evolution. Sarich and Wilson examined blood proteins to determine that apes and humans are more similar than monkeys and humans. They estimated that the divergence of lineages occurred approximately 23 mya for apes and Old World monkeys, 8 mya for gibbons and humans, and that humans and chimpanzees shared a common ancestor 5 to 6 mya. Newer research indicates that humans and chimps share more than 99 percent of their genetic makeup. The relationship between genetic differences and the geological timescale is still debated.

Early hominids faced three major adaptive problems: they were large mammals, they were terrestrial primates, and they lived in an open, tropical savanna environment. Larger mammals require more food because of higher metabolic rates. Advantages to being a large mammal include: a greater mobility that allows hominids to subsist on resources that are unevenly distributed in space and cope with the seasonality of particular foods; ability to deal with heat and cold (humans can sweat); increased longevity; and brain enlargement. Being bipedal frees up the hands and allows for other adaptations, such as toolmaking.

Between 7 and 3 mya there is evidence for several different hominids. The hominids include: Sahelanthropus tchadensis (specimen Toumai, dating from 6 to 7 mya), Ardipithecus ramidus (dating as far back as 5.8 mya), Australopithecus anamensis (4 to 4.17 mya), and Australopithecus afarensis (dating from 3.5 to 3.0 mya—best known for Lucy, and also associated with the Laetoli footprints). There is uncertainty in the field of human evolution as to which, if any, of these species lead to the human line.

Between 3 to 2.5 mya there were several Australopithecine species present; these include: A. africanus (a.k.a. Gracile Australopithecines, dating to 3 mya), robust Australopithecines (A. aethiopicus, A. boisei, and A. robustus; dating from 3 to 1 mya), and A. garhi (2.5 mya).

Beginning 2.5 mya is the first evidence of the Homo lineage with the appearance of Homo habilis (meaning “handy person”). Homo habilis differed from Australopithecus in that H. habilis was less ape-like in appearance; a rounder skull, less prognathism, and less specialized teeth. Homo habilis had a large brain (600-700 cc), walked erect, and is the first well documented to use stone tools. There are four (controversial) criteria used to classify a fossil into the genus Homo: absolute brain size of 600 cc, possession of language (identified from the inside of the skull), an opposable thumb with precision grip, and the ability to manufacture stone tools.

Reconstructing early human behavior is complicated by the poor preservation in the archaeological record; however, some inferences can still be made. Louis Leakey and other paleoanthropologists believed that concentrations of bones and stone tools represented “living floors,” or evidence of a central gathering place for Homo habilis. Other interpretations are that the concentrations are places that H. habilis butchered animals that had either died from natural causes or been killed by predators. Evidence of scavenging comes from Olduvai where 13 bones have evidence of both carnivore tooth marks and stone tool marks. Blumenschine believes that scavenging would have been more prevalent in the dry season when plant foods were not abundant. There is not much archaeological evidence of plant eating for the early hominids because this evidence does not preserve well in the archaeological record. Tooth microwear analyses shows patterns similar to modern nonhuman primates.

The stone tool industry associated with early Homo is the Oldowan industry. Toth now believes that flakes had a much more important role in the early hominid toolkit than once thought. The consumption of meat is associated with larger brain size in Homo habilis, who would have required more energy and a higher quality diet than eating plant foods alone would provide given the physiology of the hominid gut. One difference between early hominid and chimpanzee tool use is the distance that raw materials were carried from their source. Compared to chimpanzees, early hominids would carry raw materials over longer distances and to several locations. Chimpanzees generally only carry raw materials to a single site. Anthropologist Robin Dunbar has discovered evidence between group size and brain size in living primates. From this he was able to estimate that H. habilis lived in groups of around 81 individuals.

One question regarding early hominids is when the ability of spoken communication came about.

Chimpanzees in the wild communicate with gestures and vocalizations; captive chimps have been taught a variety of communication systems ranging from using American Sign Language to computers. Chimpanzees are unable to talk due to their anatomical differences from humans. Endocasts and the shape of the base of the skull both provide information that can be used to reconstruct when the acquisition of language occurred.

Through examining extant primates, it is thought that Homo habilis were highly social and that infants likely had a longer period of dependency than modern chimpanzees due to their larger brain size.

Chapter Outline

I. The Great Ice Age II. The Origins of the Human Line

A. AegyptopithecusB. Miocene Primates

III. Molecular Biology and Human Evolution IV. The Ecological Problems Face by Early Hominins

A. Adaptive Problems Dating the Past: Potassium-Argon Dating

V. Fossil Evidence: 7 to 4.0 mya A. Toumaï: Sahelanthropus tchadensisB. Ardipithecus ramidus

VI. The First Australopithecines: c. 4 to 3 mya A. Australopithecus anamensisB. Australopithecus afarensisC. Laetoli: Footprints of A. afarensis

VI. Fossil Evidence: 3 to 2.5 mya A. Gracile Australopithecines: Australopithecus africanusB. Robust Australopithecines: A. aethiopicus, A. boisei, and A. robustusC. Australopithecus garhi

VII. Early Homo: 2.5 to 2.0 mya A. Homo habilisB. A Burst of Rapid Change? Site: Malapa, South Africa: The Mystery of Australopithecus sediba

VIII. Who Was the First Human? IX. Archaeological Evidence for Early Human Behavior

A. Evidence for “Central Places”? Site: Olduvai Gorge: Tanzania, East Africa B. Hunting and Scavenging

X. Plant Foraging and “Grandmothering” XI. Toolmaking

A. The Oldowan Industry

XII. The Mind of the Earliest Humans XIII. The Development of Language XIV. Social Organization

Chapter Objectives

By the completion of the chapter the student will be able to:

1. Describe the Great Ice Age.

2. Explain the origins of the human line.

3. Communicate the evidence developed by molecular biology for human evolution.

4. Evaluate the ecological problems faced by early hominids.

5. Discuss the fossil evidence for hominids from 7 to 3 mya.

6. Discuss the fossil evidence for hominids from 3 to 2.5 mya.

7. Discuss early Homo.

8. Define the four criteria for determining membership into genus Homo.

9. Critique the archaeological evidence for early human behavior.

10. Discuss the role that grandmothers currently play, and in the past presumed to have played, in plant foraging.

11. Differentiate between animal toolmaking behavior and human toolmaking behavior.

12. Describe the Oldowan Industry.

13. Evaluate the specialized cognitive processes necessary for toolmaking.

14. Discuss the factors that probably lead to the development of language.

15. Trace archaeological evidence indicative of social organization.

Internet Assignments Related to the Chapter

1. Compare and contrast the following Australopithecines:

http://humanorigins.si.edu/evidence/human-fossils/species/australopithecus-afarensishttp://humanorigins.si.edu/evidence/human-fossils/species/australopithecus-africanushttp://humanorigins.si.edu/evidence/human-fossils/species/paranthropus-robustus

2. Using the following websites, describe why Homo habilis is a difficult species to define.

http://www.archaeologyinfo.com/homohabilis.htm http://humanorigins.si.edu/evidence/human-fossils/species/homo-habilis http://www.pbs.org/wgbh/evolution/humans/humankind/j.html

3. What were some of the factors for early hominids to become bipedal? Check out these websites for some arguments:

http://johnhawks.net/weblog/topics/bipedalism/why_be_bipedal.htmlhttp://digitalcommons.iwu.edu/cgi/viewcontent.cgi?article=1013&context=socanth_honproj

Site – Olduvai Gorge, Tanzania, East Africa

1. Olduvai Gorge – http://en.wikipedia.org/wiki/Olduvai_Gorge

2. Jaw found at Olduvai - http://news.nationalgeographic.com/news/2003/02/0220_030220_olduvaijaw.html

Dating the Past -- Potassium-Argon Dating

1.http://archserve.id.ucsb.edu/courses/anth/fagan/anth3/Courseware/Chronology/09_Potassium_Argon_Dating.html

2. http://geology.about.com/od/geotime_dating/a/K_argon_dating.htm

Site: Malapa, South Africa: The Mystery of Australopithecus sediba

1. http://www.huffingtonpost.com/2012/07/14/early-human-fossils-australopithecus-sediba_n_1672438.html

2. https://humanorigins.si.edu/resources/whats-hot/new-early-human-species-announced

Chapter Two

Human Origins

7 Million to 1.9 Million Years Ago

People of the EarthAn Introduction to World Prehistory

FOURTEENTH EDITION

By: Brain M. Fagan and Nadia Durrani

The Great Ice Age

• Pleistocene epoch (Ice Ages or Age of Humanity) - began about 1.6 million years ago (mya). – The major climate and environmental

changes that took place during the Pleistocene were the backdrop for some of the most important stages in human evolution.

– The Pleistocene epoch had constant fluctuations between warm and intensely cold global climates.

The Great Ice Age

• Pleistocene epoch

– The northern parts of Europe and North America were mantled with great ice sheets, the last retreating only some 15,000 years ago.

– There have been at least nine of these glacial periods during the last 780,000 years, which is why the Pleistocene is sometimes called the Great Ice Age.

– Interglacials, with climates as warm as or warmer than that of today, were rare, and the constant changes repeatedly displaced plants and animals from their original habitats.

The Origins of the Human Line

• Aegyptopithecus - Oligocene, some 35 million to 30 million years ago - Aegyptopithecus zeuxis, Nile Valley.

• Miocene Primates

– dental apes - hominoids with apelike teeth but with monkeylike bodies (~23 mya). Proconsul

Morotopithecus bishopi

– Kenyapithecus

– Nakalipithecus nakayamai

The Origins of the Human Line

• Bipedalism - Early hominins became bipedalover a long period of time, perhaps as a result of spending more and more time feeding on food resources on the ground.

• Bipedalism is a way of moving that is configured for endurance rather than power or speed.

• Walking is highly effective for wide-ranging foraging or running a marathon.

Molecular Biology and HumanEvolution

• Vincent Sarich and Alan Wilson - Developed a means of dating primate evolution.

– Sarich and Wilson showed that the albumins of apes and humans are more similar than those of monkeys and humans.

– They argued, apes and humans have a more recent common ancestry.

– Estimated that chimpanzees and humans last shared a common ancestor about 5 million to 6 million years ago.

Molecular Biology and HumanEvolution

• Results of the molecular clock using changes in beta globulin genes (Goodman)– split between monkeys and apes ~ 25 mya

– split between the greater and lesser apes to about 17 mya

– Gorillas split from the chimpanzee-human branch about 8 million years ago

– the human line and chimpanzees about 7 to 8 million years before present

The Ecological Problems Faced by Early Hominins

• Early hominin populations underwent adaptive changes through natural selection to solve environmental problems caused by the broader ecological community.

• Adaptive problems

– Being large mammals carrying capacity

– Being terrestrial primates

– Living in a savanna environment

Fossil Evidence: 7 to 4.0 mya

• Summary of Fossil Hominins– Toumaï: Sahelanthropus tchadensis -

between 6 million and 7 million years old. Confirms what many people have long believed.

Hominin evolution was much more complicated than was suspected a generation ago.

– Ardipithecus ramidus - found in a 4.4-million-year-old layer at Aramis in the arid Awash region of Ethiopia.

The First Australopithecines: c. 4 to 3 mya

• Australopithecus anamensis

– Complete upper and lower hominin jaws, some teeth, and limb fragments of almost 80 individuals from Allia Bay and Kanapoi on Lake Turkana, Kenya.

– These fossil finds date to about 4.2 to 3.9 mya.

The First Australopithecines: c. 4 to 3 mya

• Australopithecus afarensis

– Best known from the Hadar region of Ethiopia and from the Laetoli site in Tanzania (named “Lucy”).

– Lucy was only 1.0 to 1.2 m (3.5 to 4.0 feet) tall and 19 to 21 years old.

– The remains of at least 13 males, females, and children were also found.

– Lucy herself has recently been dated to 3.18 mya by means of a variant of potassium- argon dating that uses computerized argon laser fusion.

The First Australopithecines: c. 4 to 3 mya

• Laetoli: Footprints of A. afarensis

– Dramatic confirmation of A. afarensis

– excavated by Mary Leakey

– potassium-argon-dated to 3.75 to 3.59 mya

– The footprints came from the buried bed of a seasonal river, where thin layers of fine volcanic ash once formed a pathway for animals traveling to water holes.

Fossil Evidence: 3 to 2.5 mya

• Gracile Australopithecines: Australopithecus africanus

– Australopithecus africanus was a gracile, highly mobile hominin, marked in fossil form by small, almost delicate skulls and prognathous faces.

– Found only in South Africa, africanus is an evolutionary mystery, for no one has yet found this form in East Africa, where A. afarensis flourished.

Fossil Evidence: 3 to 2.5 mya

• Robust Australopithecines: A. aethiopicus, A. boisei, and A. robustus:

– Found in both eastern and southern Africa

– had small brains and large teeth that were specialized for chewing coarse, fibrous plant foods

– Three species - A. aethiopicus, A. boisei, and A. robustus

Fossil Evidence: 3 to 2.5 mya

• Australopithecus garhi:

– stood about 1.46 m (4 feet 10 inches) tall

– had protruding features, not unlike those of a chimpanzee

– The lower molars are three times the size of those of modern humans, the canines almost as large.

– Australopithecus garhi’s brain was only a third the size of that of a modern human.

– The legs are long and humanlike, while the arms are long and more like an ape’s.

Early Homo: 2.5 to 2.0 mya

• Sometime around 2 million to 1.8 million years ago, early forms of the genus Homo appeared, marked by larger brains, generally smaller jaws and teeth, and other features that seem to foreshadow modern human crania.

– Homo habilis Louis and Mary Leakey - Olduvai Gorge in 1960

Richard Leakey - the famous Skull 1470 in East Turkana, a large-brained, round-headed cranium that confirmed the existence of H. habilis in no uncertain terms

Early Homo: 2.5 to 2.0 mya

– Homo habilis (cont.)

about 1.3 m (4 feet 3 inches) tall and about 40 kg (88 pounds)

H. habilis would have looked less apelike than Australopithecus, around the face and skull.

The head was higher and rounder, the face less protruding, the jaw smaller.

Who Was the First Human?

• In recent years, four criteria have been generally used to assign a fossil to the genus Homo:– an absolute brain size of 600 cc – the possession of language – the possession of a modern, humanlike precision grip

and an opposable thumb – the ability to manufacture stone tools

• This definition of Homo makes a clear distinction between the hominins of earlier than 1.9 million years ago and Homo erectus and its successors who evolved after that date.

Archaeological Evidence for Early Human Behavior

• Four lines of evidence offer opportunities for testing hypotheses about early hominin behavior:

– 1. Scatters of artifacts

– 2. Manufactured artifacts

– 3. Surviving food remains

– 4. Isotopic analyses

Archaeological Evidence for Early Human Behavior

• Evidence for “Central Places”?

– All archaeology currently tells us is that the early Olduvai sites were places to which stone and food resources were carried.

– These may have been the remote predecessors of hunter-gatherer central places, which were to come into being in later times, conceivably with the regular use of fire for heat and protection.

Archaeological Evidence for Early Human Behavior

• Hunting and Scavenging

– Were these hominins full-fledged hunter-gatherers, or did they scavenge predator kills for meat? Or both?

taphonomy

microwear studies

diverse carnivore and ungulate communities

Plant Foraging and “Grandmothering”

• A scanning electron microscope focused on tooth microwear has shown that some Lower Pleistocene hominins had diets very similar to those of modern nonhuman primates.

• Grandmother Hypothesis (O’Connell) - Very often, women in their 60s and 70s are more efficient foragers than their younger female kin of reproductive age.

– By the age of 5, children can supply as much as half their daily nutritional requirements by their own efforts.

– Both mothers and grandmothers deliberately target easy-to-acquire foods such as fruit during the rainy season, which children can also take in large numbers.

Toolmaking

• Human beings manufacture tools regularly and habitually and with much more complexity than do Chimpanzees.

– The Oldowan Industry – Chipped stone tool industry found in Africa dating from 1.8 mya.

Mary Leakey

Nicholas Toth

Julio Mercader

The Mind of the Earliest Humans

• Homo habilis shared the ability of their earlier ancestors to “map” resources over the landscape, their intelligence amplified by toolmaking.

– Nicholas Toth

– Leslie Aiello and Peter Wheeler

– Steven Mithen

The Development of Language

• Despite the enhanced skill of communicating with others, the first humans probably had only the most rudimentary forms of speech, in addition to the grunts and gestures of other primates.

Social Organization

• Homo habilis may have lived in larger groups, something made possible by greater social intelligence resulting from larger brain size.

People of the EarthAn Introduction to World Prehistory

Fourteenth EditionBy: Brian M. Fagan and Nadia Durrani

Chapter Two

Human Origins

2.1 Louis and Mary Leakey examining fragments of Zinjanthropus (Australopithecus) boisei soon after its discovery.

2.2 Reconstruction of Aegyptopithecus, a primate with the skeleton of an arboreal quadruped.

2.3 Bipedalism and four-footed posture. The two major theories account for the evolution of bipedalism.

2.4 A much-simplified version of how Old World monkeys, apes, and humans evolved.

2.5 Tentative reconstruction of Ardipithecus ramidus.

2.6 Male and female Australopithecus afarensis.

2.7 Hominin footprints from Laetoli, Tanzania.

2.8 Hominin skulls compared. In the back, a gracile Australopithecus africanus; in front, the massive cranium of Australopithecus robustus.

2.9 A tentative reconstruction of Skull 1470 from East Turkana, Kenya.

2.10 Australopithecus sediba.

2.11 A provisional interpretation of the evolutionary relationships between known hominin forms after 6 million years.

2.13 Olduvai Gorge, Tanzania.

2.14 The forbidding, arid landscape of East Turkana, which was somewhat better watered 2.5 mya.

2.15 Chimpanzee using a stick as a tool to fish for insects.

2.16 Early stone technology.

2.17 Oldowan technology.

2.18 A modern hand grasps an Oldowan chopper.

2.19 A female chimpanzee grooms her infant daughter in her nest in the Gombe National Park, Tanzania.