Ch2 The First Humans 01 26 2014 Introduction The Dawn of Humanity created on their way to the present Archaeology study of bones and myriad other artifacts that past humans Earliest human ancestors thought to be more than 6 million years old First tools and other artifacts date back to 2 6 million years ago First half of chapter concentrate on human skeletal remains and footprints that provide earliest evidence left behind Second half of chapter Consider appearance of the genus Homo and earliest tools and other materials that make up the archaeological record 3 75 million year old footprints found at site of Laetoli in East Africa are the most dramatic and important evidence we have to early humans as two footed animals ancestors becoming bipedal appears to be the first branch off of apelike Primates because we have grasping hands flexible limbs and highly developed sense of vision share with other primates Hominoidea because of shape of teeth absence of tail and swinging arms taxonomic group includes apes and humans Earliest Hominoidea appeared approximately 25 million years ago Apes generally distinguished from monkeys and other primates by larger size distinctive teeth greater sociability absence of a tail and reduced sense of smell New group of animals called dryopithecines emerged between 17 and 12 million years ago during Miocene epoch had several features that suggest they were the probable ancestors of both living apes and humans o known primarily from fossil teeth that have survived o Apparently very successful at arboreal adaption ranging over Africa Asia and Europe o Between 9 and 4 million years ago climate drastically changed along Indian and Eurasian continental plates causing climates from East Africa to East Asia to be drier and more seasonal Quite possible that some apes were driven to the open savanna and along the human line At some point after 10 m y a one of African primate species took path towards humanness fossil time period is very scanty Fossil discovery of this creature maybe in Sumbruru Hills of Kenya Fragment of an upper jaw dating 9 8 m y a characteristics of chimpanzee gorilla human ancestor Genetic and molecular evidence indicates that humans were most closely related to chimpanzees but then began to diverge between 5 and 6 m y a o Evidence from Central and East Africa suggests this date may have even been earlier Human because we have a skeleton designed for upright walking grasping hands with opposable thumbs capable of both strength and precision movement lost the grasping opposable toes to other apes small flat teeth and lack large slashing canines of other primates pronounced nose compared with that of apes and face that sites beneath our brain case rather than in front of it lack fur and have more sweat glands than hair follicles conspicuous penis and breasts have sex face to face care for young over longer period of time make and use tools to alter environment and make lives more secure and comfortable often act according to reason rather than on instinct large brain relative to our size enhanced intelligence and complex repertoire of behaviors known as culture speak a language full of meaning and metaphor But then what of our ancestors most readily found characteristics of ancestors are upright posture larger brains and tools Major questions in human evolution concern when where and why distinctive characteristics appeared what is preserved in layers of geological time Paleoanthropology study of human evolution attempts to answer these questions using evidence from fossils and artifacts Must turn to Africa best evidence from Hadar Laetoli Swartkrans and Olduvai Concept The Family Tree 01 26 2014 In almost all incidences fossil remains of earliest hominin ancestors are very fragmentary poorly preserved and disturbed by natural forces time and nature Since mid 1700 s scientists have classified newly discovered members of plants and animals into organizational system Kingdom Phylum Class Order Family Genus Species Broad to specific Modern humans are members of family Homininae genus Homo and species sapiens Determining genus and species of early humans is very difficult o Fragmented fossils of few parts of a few hundred individuals o Determining age of fossils is hard o Questions about if species existed contemporaneously or sequentially Paleoanthropology morel like court of law than physics lab whenever new fragment is discovered have to reassess and even redraw the entire family tree among the apes Even words to describe the category of early human ancestors are controversial new fossil finds have forced a reconsideration of terms because it gets harder to distinguish first humans from their closest relatives Term hominoid refers to all present and past apes and humans has been used for many years as generic term But new term hominin being used in place of hominoid o Genetic studies show not all apes descended from common ancestor means that on strict taxonomic level chimps and gorillas are hominoids Term used to describe those species clearly in line of human evolution not other apes All hominins are hominoids but not all hominoids are hominins Recent years have shown major changes in field of paleoanthropology features of fossil material found in Chad central Africa and from usual places of East and South Africa Thickness of tooth enamel evidence for bipedalism and tree climbing and size differences between sexes sexual dimorphism important role in discussion Chad new controversial fossil species found designated as Sahelanthropus tchadensis combines ape and human characteristics flat face and habitual bipedalism distinguish it as a human ancestor Dates to between 7 and 6 m y a making it our oldest known ancestor In Tugen Hills of Kenya fossil bones Orrorin tugenensis date to 6 m y a a CAT scan of fossil femur indicated habitual bipedalism arm bones suggest tree climbing thick enamel like humans East Africa Middle Awash area of Ethiopia 17 fossils including teeth skull and arm bones found by research team directed by Tim White of UC Berkeley Fossils lie directly under volcanic deposit dating to 4 4 m y a designated Ardipithecus ramidus species exhibits combination of human and chimpanzee like features o Sometimes described as the oldest skeleton of human ancestor Suggest ancestor most likely walked on two legs Meave Leakey and colleagues named a new genus and species Kenyapithecus platyops flat humanlike face but ape sized brain Dates