Tiêu đề Brian M. Fagan_ In the Beginning ✅

Lecture Two In the Beginning Scope: In this, the second lecture, we begin our narrative of human prehistory, with an account of the earliest humans of all. Lecture Two covers human origins from before 7 mya up to 3 million years before present. The first part places humans among the primates and in the suborder Hominidae. We then consider the fundamental anatomical and behavioral changes that may have occurred among hominids before and after they separated from their common ancestor with chimpanzees between 7 and 5 mya. The next part of the lecture examines the different fossil forms, which define the earliest stages of human evolution, and concludes that we must conceive of human evolution as a form of conceptual bush. The lecture ends with the descendants of Australopithecus afarensis splitting into different lines about 3 mya. Outline I. Victorian biologist Thomas Huxley called human origins the “question of questions” for humankind. As long ago as 1863, he drew attention to the close anatomical relationships between humans and apes, a highly controversial piece of research at the time. In 1871, Charles Darwin, of evolution and natural selection fame, theorized that Africa, with its rich ape populations, would reveal much about human evolution. The research of a century and a half has proved them correct. A. Today’s paleoanthropologists draw on researches in numerous academic disciplines to tell the story of early human evolution. Molecular biology in particular has helped pinpoint the moment when humans separated from our closest living non-primate relatives, the chimpanzees. B. All of us are members of the order Primates, which includes most tree-loving placental mammals. There are two suborders: anthropoids (apes, humans, and monkeys) and prosimians (lemurs, tarsiers, and other “premonkeys”). C. The many similarities in behavior and physical characteristics between the hominids (primates of the family Hominidae, which includes modern humans and their ancestors) and pongids (our closest living primate relatives) can be explained by identical characteristics that each group inherited millions of years ago from a common ancestor. 1. The basic anatomical pattern of the large hominids appeared in the Middle Miocene epoch, about 18 to 12 mya. By the Late Miocene, some 8 to 5 mya, tree-loving apelike animals with long arms and legs abounded in Africa, the ancestors both of modern non-human primates and hominids. 2. The albumin protein substances found in primate blood have evolved at a constant rate. Thus, the difference between the albumins of any pair of primates can be used to calculate the time since they separated from each other. 3. Chimpanzees, our closest living relatives, diverged from a common ancestor shared with humans about 5 to 6 mya. II. Dramatic environmental changes affected tropical Africa, the cradle of humankind, about 5 mya and had a profound effect on the evolution of the first humans. At this time, primates abounded in thick forests, in more wooded country, and on the open savanna grassland, where they had to stand upright to survive. A. An upright posture and a bipedal gait are among the most characteristic human features. In the trees, a four-footed posture is highly effective. One walks on one’s knuckles like a football lineman. Endurance and the ability to cover long distances are vital in open country, such as the savannas, which covered much of East Africa between 5 and 1 mya. Bipedalism made this easier and freed the hands for tool making. 1. After about 10 mya, many primates spent more and more time on the ground, coming “down from the trees.” 2. By 5 mya, Africa’s climate was drier, favoring more open country in many areas. Savanna living presented new challenges, among them, the necessity of finding food over large areas. Mobility was essential. B. Plant foods were rarer and more widely dispersed on the savanna. Meat became a larger part of the diet as a way of coping with long periods of plant scarcity. Our earliest ancestors became omnivorous and highly mobile—a characteristic of human foraging for thousands of years in later times. 6 ©2003 The Teaching Company Limited Partnership

Essential Reading: Don Johanson and Maitland Edey, Lucy. Roger Lewin, The Principles of Human Evolution, parts 1–4. Ian Tattersall, The Fossil Trail: How We Know What We Think We Know about Human Evolution. Supplementary Reading: Brian Fagan, People of the Earth, chapter 2. Roger Lewin, Bones of Contention. Questions to Consider: 1. What were the most important qualities for a hominid “coming down from the trees”? 2. How should we think of human evolution, conceptually? Why is the old idea of linear evolution outmoded? 8 ©2003 The Teaching Company Limited Partnership