Human Origins and Evolution A 5 7 Billion years ago humans evolved from apes I II Primate Family Tree A B Nails instead of claws human ape similarities III Ape Family Tree A 5 7 billion years ago IV Earliest Hominin Sahelanthropus tchadensis 1 Humans didn t start walking on two hind legs A V Important Early Hominins B Found in 2002 C From about 75 million years ago D Shape of the skull varies from apes because of brow muscle A Ardi Ardipithecus ramidus 1 4 4 million years ago is when he lived B Lucy Australopithecus afarensis 1 1974 found in Ethiopia 2 One of the most complete skeletons we ve ever identified 3 First fully bipedal hominin to walk majorly on two feet 4 3 2 million years old C 5 3 million years ago humans believed to be BIPEDAL D Humans have evolved getting larger E Advantages of Bipedal 1 Able to use hands 2 Taller able to see things better 3 Oxygen is not as shallow VI Hominin Lineages A B Neanderthals were alive the same time homo sapiens however Neanderthals disappeared C Homo ergaster was believed to have left the African continent 2 million years ago 1 They are believed to be the first VII Origins A Multiregional Hypothesis B Out of Africa Hypothesis VIII Variation in restriction sites in human populations A Analysis of mitochondrial DNA B Digested with different restriction enzymes 1 Enzymes that cut DNA at a specific sequence C Used this to construct a phylogenic tree Phylogenetic Tree Based on Restriction Site Variation A Homo sapiens evolved around 200 00 years ago Support for the out of Africa theory IX X A XI Neanderthals 1 Considered modern A Cro Magnon B Neanderthal C XII The Evidence for and Against Interbreeding A Mitochondrial DNA comes strictly from the mother B Did Neanderthals and modern humans interbreed 1 Based on genome yes 2 Based on Mitochondrial DNA no a Could have been lost through genetic drift b Female Neanderthals did not interbreed with homo sapiens i But males could have C XIII Becoming Bipedal A Changes in spine 1 Shift in position of forum and magnum 2 Change to an S shape B Skull shifted 1 Centered towards spine C Pelvis Altered D Leg Bones Different 1 Longer for longer strides E Feet 1 More narrow than a chimpanzee 2 Thicker and more stabilizing heel bone XIV Neoteny A Neoteny the retention by adults in a species of traits previously seen only in juveniles 1 Adult humans share many characteristics with juvenile chimpanzees B XV Brain Size A Things that led to increase in brain size 1 Language 2 Social interaction with others 3 New tools B Humans have bigger brains than most C Which of the following are thought to have contributed to the increase in brain size in humans 1 Tool Use 2 Social Living 3 Language 4 All of the Above XVI FOXP2 A What makes us human if we are only 1 different than chimpanzees apes 1 Two amino acid differences a This gene is involved in development of human b 6 7 million years ago difference in gene FOXP2 B A XVII Human Migratory Routes B 60 000 years ago started C 1 difference in the population 1 Compared to other animals there is not a lot of genetic variation 2 Small group that moves away from the rest a Founder event b Paripatric Genetic Drift D When we compare levels of genetic variation in a contemporary African population to that of a contemporary non African population we find there is 1 More variation in the African population 2 More variation in the non African population 3 Equal Variation in both populations E Why is there less genetic variation in the non African populations 1 Non African populations represent founder events 2 Non African populations have high mutation rates 3 Non African populations experience high rates of Natural Selection XVIII Natural Selection Explains Human Differences A Darker skin tones live in hotter areas B Lighter skin tones live in colder areas XVIV Influence of Culture on Evolution A XX Cultural Influence in Other Species A XXI Language A CHAPTER SUMMARY 24 1 ANATOMICAL MOLECULAR AND FOSSIL EVIDENCE SHOWS THAT THE HUMAN LINEAGE BRANCHES OFF THE GREAT APES TREE Anatomical features indicate that primates are a monophyletic group that includes prosimians monkeys and apes The apes in turn include the lesser and great apes The great apes include orangutans gorillas chimpanzees and humans Analysis of sequence differences between humans and our closest relatives chimpanzees indicate that our lineage split from chimpanzees 5 7 million years ago Lucy an unusually complete specimen of Australopithecus afarensis demonstrates that our ancestors were bipedal by about 3 2 million years ago Human lineage fossils occur only in Africa until about 2 million years ago when Homo ergaster migrated out of Africa to colonize the Old World 24 2 PHYLOGENETIC ANALYSIS OF MITOCHONDRIAL DNA AND THE Y CHROMOSOME SHOWS THAT OUR SPECIES AROSE IN AFRICA Studies of mitochondrial DNA mtDNA suggest that the time back to the common ancestor of modern humans is about 200 000 years implying that modern humans Homo sapiens arose in Africa the out of Africa theory The mtDNA out of Africa pattern is supported by Y chromosome analysis which also shows a recent African origin of modern humans Analysis of Neanderthal DNA from 30 000 year old material indicates that as the ancestors of non African humans emigrated from Africa they interbred with the Neanderthals Our species originated in Africa and subsequently colonized the rest of the planet starting about 60 000 years ago 24 3 DURING THE 5 7 MILLION YEARS SINCE THE MOST RECENT COMMON ANCESTOR OF HUMANS AND CHIMPANZEES OUR LINEAGE ACQUIRED A NUMBER OF DISTINCTIVE FEATURES The development of bipedalism involved a wholesale restructuring of anatomy Neoteny is the acquisition of sexual maturity in an otherwise juvenile state humans are neotenous exhibiting many traits as adults that chimpanzees exhibit as juveniles There are many possible selective factors that explain the evolution of our large brain including tool use social living and language FOXP2 a transcription factor involved in brain development may be important in language as mutations in the gene that encodes FOXP2 are implicated in speech pathologies 24 4 HUMAN HISTORY HAS HAD AN IMPORTANT IMPACT ON PATTERNS OF GENETIC VARIATION IN OUR SPECIES Because our ancestors left Africa very recently in evolutionary terms there has been little chance for genetic differences to accumulate among geographically separated populations Humans have very little genetic variation with only about 1 in every 1000 base
View Full Document
Unlocking...