Transcript of Slides- Introduction Lecture ANTH 18630 Fall, 2011 Slide 3 A phylogenetic tree is a visual representation of how taxa are related to one another. The points labeled, for example, ‘y’ and ‘x’ are called ‘nodes’. Nodes indicate most recent common ancestors, abbv. MRCA. Each node branches into two lines, called lineages. Lineages are comprised of both extinct and living taxa. The taxa (fish, frog, lizard, mouse, human) shown at the ‘tips’ of each lineage are living representatives of the lineage. These are called ‘tip taxa’. In this phylogenetic tree, is the frog more closely related to the fish or the human? Slide 4 Most people look at the phylogenetic tree on the left and say the frog is more closely related to the fish because the frog is placed beside the fish. In the tree on the right, node ‘x’ has been rotated, moving the frog furthest from the fish. The key to answering this question is not to focus on the ‘tip taxa’. Rather, focus on the ‘nodes’ or most recent common ancestors. Node ‘y’ is the common ancestor of the lineages leading to fish, frog, lizards, mouse, and human. Node ‘x’ is the common ancestor of the lineages leading to frog, lizard, mouse, and human. Node ‘y’ is a earlier ancestor than ‘x’. All the taxa that derive from node ‘x’ are tetrapods, making all the taxa more closely related to one another than any is to fish, a non-tetrapod. So, the frog is more closely related to the human because frog and human share a more common recent ancestor (node ‘x’). Slide 7 This is a phylogenetic tree depicting living representatives of the Primate Order (red branches on tree). Mouse, a non-primate mammal, is shown as an outgroup (green branch on tree). Not all primate taxa are shown. As you can see from the figure, the lineage leading to primates diverged from the common ancestor with the lineage leading to rodents approximately 75 million years ago. Galagos are living representatives of the earliest primates, which diverged from common ancestors as early as 63 million years ago. More recent primate lineages include the New World monkeys such as the capuchin monkey, Old World monkeys such as the baboon, apes such as chimpanzee, and humans (we are the only living representative of our lineage). The lineage leading to chimpanzee and the lineage leading to human diverged from their common ancestor only about 7 million years ago. Thus chimpanzee and human are the closest living primates. As we will learn in class, there are fossil representatives along each lineage. The last third of this class will focus on the fossil lineages leading to human AFTER divergence from the common ancestor with chimpanzee. This lineage is called the hominid lineage; we are the only remaining living representatives of the hominid line. Slide 8 Homo erectus is an important hominid fossil lineage. It shares our genus (Homo) but is a separate species. Slide 9 Homo neanderthalensis is another important hominid fossil lineage. Recently scientists have been able to sequence the DNA genome of Neandertals and compare it with that of our own. Slide 10 All members of our species, Homo sapiens, shared a most recent common ancestor approximately 200,000 years ago. Cro-Magnon are early Homo sapiens that lived in France. Slide 11 FIGURE 1.4. The Six Big Events of Human Evolution: Bipedalism The upright, bipedal (two-footed) gait was the first hallmark feature of our hominid ancestors.Transcript of Slides- Introduction Lecture ANTH 18630 Fall, 2011 Slide 12 FIGURE 1.4. The Six Big Events of Human Evolution: Nonhoning Chewing. Humans’ nonhoning chewing complex (left) lacks large, projecting canines in the upper jaw and a diastema, or gap, between the lower canine and the first premolar. The chewing complex of apes such as gorillas (right) has large, projecting upper canines and a diastema in the lower jaw to accommodate them. Slide 13 FIGURE 1.4. The Six Big Events of Human Evolution: Speech Although other animals use noises and calls to communicate basic ideas, only humans can speak and, through speech, express complex thoughts and ideas. The shape of the hyoid bone is unique to hominids and reflects their ability to speak. Slide 14 FIGURE 1.4. The Six Big Events of Human Evolution: Dependence on Material Culture Humans’ production and use of stone tools is one example of complex material culture. The tools of our closest living relatives, the chimpanzees, do not approach the complexity and diversity of modern and ancestral humans' tools. Slide 15 FIGURE 1.4. The Six Big Events of Human Evolution: Hunting Humans’ relatively large brains require lots of energy to develop and function. Animal protein is an ideal source of that energy, and humans obtain it by eating animals they hunt. To increase their chances of success in hunting, humans often employ tools and cooperative strategies. Slide 16 FIGURE 1.4. The Six Big Events of Human Evolution: Domestication of Plants and Animals Humans domesticate a wide variety of plants and animals, controlling their life cycles, using them as