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Anthropology: Human Evolution and Adaptations Evolutionary Theory Charles Darwin 1809-1882 Published Origin of the Species (1859) Galapagos Islands – observed different species of finches Controversial ! Evolution Evolution refers to change over time, or transformation over time. Evolution assumes that all natural forms arose from their ancestors and adapted over time to their environments. There are numerous ways in which evolution occurs, the most noted are Natural Selection and Adaptation. Darwin’s Theory – Natural Selection 1. Heritability: Organisms inherit characteristics from their parents 2. Variation: there is a lot of variation within a species 3. Environmental Fitness: Those traits that allow an individual to survive to reproductive age – to pass on to offspring Darwin’s Finches An example of Variation Peppered Moth UK – example of natural selection White and Black moths (Variation) Food source for birds Before Industrial Rev. most moths – white better camouflaged against white lichen (Enviromental Fitness) Industrial Rev – coal dust turned environment black, now black moths better camouflaged. Black moths now surviving to reproduce and pass their colour to next generation (Heritability) Now, most moths are black (natural selection) Key Concepts in Evolution Adaptation Variation Natural Selection – – random genetic mutations occur within an organism's genetic code, the beneficial mutations are preserved because they aid survival Survival of the Fittest – – only the necessary characteristics survive – and the species who acquire those characteristics will remain and reproduce Artificial Selection Human breeders have produced dramatic changes in domestic animal populations by selecting individuals to breed. Breeders eliminate undesirable traits gradually over time. Examples? Evolution – evidence Physical Anthropologists Look at: 1. Fossil, bone, stone remains (using dating techniques) 2. Microscopic analysis – pollen, scratches on bone 3. Experiments – flake stone techniques Human Evolution Hominids Human Evolution Primate - Largebrained, mostly treedwelling mammals with three-dimensional color vision and grasping hands. Humans are primates. Hominid: is any member of the biological family Hominidae (the "great apes"), including the humans, chimps, bonobos, gorillas and orangutans The oldest hominids belong to the genus Australopithecus: Australopithecus Australopithecus Australopithecus Australopithecus afarensis africanus (example) robustus boisei Australopithecus afarensis Our most ancient ancestor is Australopithecus afarensis. They lived roughly 4 - 2.75 million years ago. " Lucy" is the skeleton remains of an Australopithecus afarensis which has made us aware of this species. Hominids - The Human Lineage Homo Habilis Homo Erectus (example) Neanderthals Cro-Magnons Homo Sapiens Homo Erectus They inhabited the regions of southeastern and eastern Asia until approximately 300 000 years ago. Europe, India, China and Indonesia have all yielded evidence of Homo erectus. – "Turkana Boy" was an African discovery, which shows that Homo erectus had a similar body size to humans. The period that this boy lived in was 1.6 million years ago. Homo erectus, according to some studies, made use of fire and occupied caves. Habitual Bipedalism Bipedalism – to habitually walk on two legs. Humans only primate with this adaptation What had to happen for us to stand up straight? Bipedalism continued Structural changes required for us to walk upright: 1. S-shaped spine Arched foot Pelvis – shorter and wider More gluteus muscles Fewer head / neck muscles – therefore a bigger brain 2. 3. 4. 5. Advantages of being bipedal Free hands for carrying Can walk longer distances Can have a continuous good view of surroundings Disadvantages of being bipedal Highly dangerous birthing process Offspring very dependent and weak because the skull must grow outside of the womb Hominids and Brain Size Humans have the largest brain for our body mass compared to other mammals Refinements in hand structure A fully opposable thumb gives the human hand its unique power grip (left) and precision grip (right). Tooth size comparison Hominid (human), Primate differences: Primates Social structures Dominance Hierarchies Silverbacks and alpha males in a group Grooming Related to the hierarchies Stress release Hominids / Humans Pair Bonding AND Group Living Humans are the only primates to have both social characteristics simultaneously Hominid (human), Primate differences Primates Reproduction Estrus cycle (in heat) No choice of when to mate Who gets to mate when ties into dominance and grooming hierarchies Hominids / Humans No estrus cycle Choice in when to mate Hominid (human), Primate differences Primates Mother – Infant relationship Long infant dependency compared to other mammals Important in learning survival skills and culture Hominids / Humans Longest infant dependency period of all primates Hominid (human), Primate differences Primates Communication Facial displays, call, touch Hominids / Humans Speech centre in the brain Culture Dagger Carvings – Stonehenge Horse in world's oldest painted prehistoric cave, 15,000-10,000 BC Lascaux, France Humanity and our Variations Our bodies are essentially 50 000 years old. Now culture, not physical evolution enables us to adapt very quickly to a changing environment Race - Cultural construct – does not physically exist Skin Colour - Legitimate Explanations for Human Variation Sunlight is the best source of vitamin D (necessary for healthy bones) Light skin absorbs vitamin D and burns more easily than darker skin Paler skin is found in areas further from the equator where there is less sunlight (environmental Fitness) Skin colour (variation) Skin Colour - Legitimate Explanations for Human Variation Darker skin provides better protection from UV rays Darker skin is found in areas closer to the equator where there is more and stronger sunlight (environmental Fitness) Skin colour (variation)