Earth 125 1st Edition Lecture 19 Outline of Last Lecture I. Appearance of PrimatesII. HumansIII. Environment Corresponding to the Transitional Forma. Glaciers, climate changeOutline of Current Lecture II. Human EvolutionIII. Brain size IV. Biogeography of humansCurrent LectureI. Bipedality & Evolutiona. Obligate bipedality requirementsi. Foramen magnum1. Foramen in back of head for “knuckle-walkers”2. Under skull for humans/obligate bipedsii. Shape of spine1. Straight spine for chimps2. s-shaped spine for humans/obligate bipedsiii. Pelvis muscles1. Small muscle pelvis for chimps2. Large muscle pelvis for humansiv. Knee 1. Bent knee for chimps2. Extend/lock knee for humansv. Big toe1. Opposable big toe, no arch for chimps2. Big toe in place of other toes, pronounced arch for humansb. Why did bipedalism evolve?i. A response to increasing areas of open savannah1. Must traverse savannah in order to find food in rainforestsii. Cooling of climate (increased drying in Africa), fragmentation and reduction of forest, increase of savannahiii. Bipedality has a less energetic cost of walking than chimps’ knuckle-walking1. Humans were four times more efficient than the chimpsiv. In crossing the savannah, sun is beating down. Increased temperature = body water loss1. When sun is directly above the sky, it is hitting more surface area of the chimp than the human2. Shadows cast by knuckle-walkers (top) and bipeds (bottom)v. Bipedals have an edge in terms of heat loading – receive more cool breeze and less heat radiating from the groundc. Persistence hunting: running and tracking until prey falls from exhaustioni. Bipedals obviously have the advantage ii. Humans have a low heat load and sweat glandsII. Brain Sizea. Was Lucy a modern human?i. Jaws and teeth1. Less expansive teeth set in humansii. Lucy and some of her contemporaries were bipedal, much like modern humans and unlike chimps, etc., but in terms of skull and jaws, they were more chimp-like than modern human-like. Commonlyreferred to as australopithecinesb. Relative brain size in primates: bigger than in other groupsi. Relative brain size in Homo: bigger than in other primatesc. Development of Hominid Braini. At 2my, we find fossil finds in which skull was measured to show capacity of brain to be twice as much as beforeii. Changes in Social/Cultural behavior1. Crushed bones show use of tools – stoneIII. Biogeographya. Members of genus homo move from Africa to Asia, Europei. Tools help this relocationii. Glaciers in North and deep Southb. Neanderthals: Homo neanderthalensisi. Evolve outside of Africa – near East, Europe, late Pleistoceneii. Short bodies, but more robustiii. Biogeography: Went extinct 30,000-40,000 years ago1. Not an African distributionc. Anatomically Modern Humans (Homo sapiens)i. 200,000-Presentii. Earliest Appearance in Africaiii. Different shape in skull compared to Neanderthalsiv. Evidence of changes in social/cultural behavior1. Cave art2. Deliberate burialsd. Controversies? i. How many species of Australopithecines; how many of Homo?ii. Out of Africa vs. Multiregional1. What happened in last 200,000 years?2. Support from molecular data for Out of Africa