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Chapter 26.3: Primates and Human Origins Mrs. Bertolotti Essential Question How have humans descended from earlier forms during the process of evolution? What characteristics do all primates share? What is a primate? Primates have: A) Binocular visionvision- the ability to merge visual images from both eyes Thus results in depth perception and a 33-D view of the world B) A wellwell-developed cerebrumcerebrum- results in more complex behaviors C) Relatively long fingers and toestoes- typically 5 and are flexible What characteristics do all primates share? Opposable thumb D) Arms that can rotate around their shoulder joints 1 Evolution of Primates What are the major evolutionary groups of primates? Humans & other primates evolved from a common ancestor that lived more than 65 million years ago Early in the history of primates, primates split into two groups. Primates in one of these groups look very little like typical monkeys. This group consists of lemurs and lorises The other group includes tarsiers and the anthropoids, the group that includes monkeys, great apes and humans Therefore, primates evolved from 2 of the earliest branches: 1. prosimians 2. anthropoids Prosimians Are alive today Small, nocturnal primates with large eyes that are adapted to seeing in the dark Example: lemurs of Madagascar Anthropoids Humans, apes, and most monkeys belong to this category Smaller eyes-eyes--day day active primates Color vision Larger brains Split into 2 categories early in evolutionary history and became separated during continental drift 1. New World monkeys Found in North and South America Examples: Squirrel and spider monkeys Live almost entirely in trees (arboreal) Possess a prehensile tailtail- a tail that can coil tightly enough around a branch to serve as a ―fifth‖ hand 2. Old World monkeys found in Africa and Asia Example: Macaques Spend time in trees but lack a prehensile tail. Great apes called hominoids hominoids-- ex. Chimpanzees and humans Chimps share approximately 99% of human DNA A New World Monkey using his prehensile tail 2 Anthropoids Anthropoids— Anthropoids —3 categories Monkeys Have tails Old World— World—Asia and Africa New World— World—Central and S. America Apes NO TAILS Larger brains than monkeys Chimps, gibbons, orangutans, bonobo,, etc. bonobo Humans Our closest genetic primate relative is? THE CHIMPANZEE What are the major evolutionary groups of primates? What adaptations enabled later hominine species to walk upright? Hominid evolution Hominid evolution Between 66-7 million years ago, the lineage that led to humans split from the lineage that led to chimpanzees. Adaptive radiation may be responsible for the evolution of early hominids The hominoids in the lineage that led to humans are called hominines hominines.. Hominines include humans and other species closely related to us than chimpanzees. Example: Neanderthals. Hominines evolved the ability to walk upright, use grasping thumbs, and large brains. The skull, neck, spinal column, hip bones, and leg bones of early hominine species changed shape in ways that enabled later species to walk upright. Being bipedal (ability to walk on two feet) was important as it freed up both hands to use tools. The opposable thumb allowed the tips of the fingers to touch the thumb, enabling the grasping of objects and the use of tools. 3 Hominid vs. chimpanzee Human vs. gorilla Features Skull Spinal cord Arms and hands Pelvis Thigh bones Human Atop S-shaped spine Exits at bottom of skull Arms shorter than legs; hands don’t touch ground when walking Bowl-shaped Angled inward, directly below body Gorilla Atop C-shaped spine Exits near back of the skull Arms longer than legs; hands touch ground when walking Long and narrow Angled away from pelvis Chimps most closely related primate to humans— humans —99% similarity in the sequence of our genes! Human’s jaw more arc shaped with smaller canines; chimps’ U with larger canines and larger gaps. Hominid spine S– S– chimps’ is C shaped Hominid pelvis is bowlbowl-shaped, chimps’ long Hominid thigh bones taper in— in—chimps’ out The hominine hand evolved an opposable thumb that could touch the tips of the fingers, enabling the grasping of objects and the use of tools. Hominine Evolution What adaptations enabled later hominine species to walk upright? What is the current scientific thinking about the evolution of humans? 4 Early Hominids Genus Australopithecus LUCY 3.5 million years old Lucy Australopithecus afarensis Lucy Fossil found in Africa Hominids Hominids— —shape of pelvis and femurs showed they were bipedal. Short Short— —3’6’’ Brain size of chimps Jaws more rounded than apes Teeth like humans 40% complete Female SKULLS Lucy had a small skull like an ape, but she wasn’ wasn’t one. LUCY APE •Showed us: •walked upright first •brain size grew AFTER. SKULLS A. afarensis (Lucy) Homo sapien LUCY She walked upright She was a bipedal hominid Bowl Bowl--shaped pelvis Thigh bones taper in Locking knee joint 5 LUCY VS. APE Early Hominids • Genus Australopithecus A. afarensis • Genus Homo Homo habilis H. erectus H. sapiens Time NOT A COMPLETE LIST! THERE ARE OTHERS! Homo habilis Homo sapiens APES Homo erectus Homo habilis transitional species Australopithecus afarensis Means: Handy man Small structure like Lucy Skull 2X’s the size of Lucy 2- 1.8 mya in Africa Tools made of bone and stone. common ancestor to ape and H. sapiens Where Did H. sapiens evolve? Homo erectus Java man / Peking man Africa / Asia / Europe Larger than H. habilis Larger brain Excellent tools, used fire 1.5 mya – ―immediate‖ ancestor Two hypotheses: Out of Africa: states H. sapiens evolved IN Africa and spread to rest of world Multiregional Out of Africa hypothesis supported by most evidence. H. erectus left Africa and THEN evolved into H. sapiens 6 Neanderthals Out of Africa - But When and Who? Researchers agree that our genus originated in Africa and migrated from there to populate the world. Some current hypotheses about when hominines first left Africa and which species made the trip are shown in the figure.. figure More recent DNA data suggest that a small subset of those African ancestors left northeastern Africa between 65,000 and 50,000 years ago to colonize the world, supporting the outout-of of--Africa hypothesis. Newsflash! A comparison of DNA sequences of humans and Neanderthals, the species of hominid that existed from roughly 400,000 to 30,000 years ago, revealed some intriguing findings, indicating, for instance, that at some point after early modern humans migrated out of Africa, they mingled and mated with Neanderthals, possibly in the Middle East or North Africa as much as 80,000 years ago. ago. If that is the case, it occurred significantly earlier than scientists who support the interbreeding hypothesis would have expected. Comparisons with DNA from modern humans show that some Neanderthal DNA has survived to the present. Moreover, by analyzing ancient DNA alongside modern samples, the team was able to identify a handful of genetic changes that evolved in modern humans sometime after their ancestors and Neanderthals diverged, 440,000 to 270,000 years ago. The absence of Neanderthal DNA in the genomes of the two presentpresentday Africans indicates that interbreeding occurred after some root population of early modern humans left Africa but before the species evolved into distinct groups in Europe and Asia. Read more: http://www.time.com/time/health/article/0,8599,1987568,00.html#ixzz0p2EmJ8Pc Homo neanderthalensis discovered in Neander Valley Went extinct Massive skulls, protruding brows Great controversycontroversy- did they die off (genes no longer present in gene pool) or did they evolve with us (interbred so genes still in our gene pool)? Data indicates that interbreeding occurred in certain populations. Modern H. sapiens probably evolved in Africa and replaced Neanderthals. Neanderthals are closely related to us but we are not descended from themthem- instead we share a common ancestor. NEWSFLASH!!!!! 2009 Recent analysis of Ardipithecus ramidus ramidus… … aka ―Ardi ―Ardi‖‖ found in 1994. Lived 4.4 million years ago in what is now Ethiopia The last common ancestor shared by humans and chimpanzees is thought to have lived six or more million years ago. A hominid with opposable big toes like chimps and apes 1.2 million years OLDER than Lucy, and our oldest known common ancestor with other primates (4.4 mya mya)! )! 47 inches tall Show that chimps have actually evolved MORE than humans since our common ancestor APES Mated???? Homo neanderthalensis Homo sapiens “ARDI” Ardipithecus ramidus transitional species Homo erectus Homo habilis Australopithecus afarensis common ancestor to ape and H. sapiens ARDI????? 7 “Race” and evolution What is the current scientific thinking about the evolution of humans? The considerable range of observed phenotypic variation in human populations may reflect, in part, distinctive processes of natural selection and adaptation to variable environmental conditions. Race is characterized by the color of an individual’s skin color and their ancestry. The former, most widely recognized as an indication of one’s race, is accompanied by the presumption that the genetic and biological causes responsible for it, originate from people with a great degree of genetic variations within the human species. The development of varying skin pigmentation is not an influential enough of a difference to divide the human species into races. Skin color is merely a reaction to an environment. Race is a concept of society that insists there is a genetic significance behind human variations in skin color that transcends out ward appearance. However, race has no scientific merit outside of sociological classification. There are no significant genetic variations within the human species to justify the division of “ races.” Essential Question How have humans descended from earlier forms during the process of evolution? 8