EARTH 125 1st EditionFinal Exam Study Guide: Lectures 18-24Lecture 18What are significant differences in characteristics between primates and other mammals? Whatare significant differences in characteristics between primates and humans?Primates have molar teeth, they are often found in trees and thus have flexible arm and shoulder joints, they do not have a tail, they are quadrupedal, and have larger, complex brains. Within the primates are humans. Humans have increased encephalization, obligate bipedality, increased manual dexterity, speech, technological innovation, cultural transmission of knowledge, delayed maturation (increased learning period), and complex social behavior. Regarding bipedality, there were modifications made in order for humans to be bipedal rather than knuckle-walkers. Some of these modifications result in our back problems, but ultimately make us more energy efficient. Humans have a pelvic tilt, larger leg muscles (but shorter and less muscular arms), extension of vertical legs, our sacrum is tilted, our line of gravity is close to support structures, and our pelvis is broader.Is there evidence in the fossil record for human evolution from chimps to humans?Yes, and a lot of evidence for transitional forms from great apes to humans is found in Africa. Particularly around active volcanoes, which lead to a lot of volcanic ash and bury organisms, there is great evidence that is excellent for dating (radioisotopes). In 1974, Don Johanson found “Lucy,” a Australopithecines. Her skeleton (3.2 my) was enough evidence (from her lower skeleton) to inform scientists of locomotory behavior. Her leg alignscloser to the Modern Human skeleton than a chimp skeleton. Her skeleton was small, but from the perspective of a pelvis, femur, and foot, Lucy looks very human – bipedal. There are other similar cases to Lucy – all prove transitional forms from chimps to humans.Lecture 19What are the requirements in order be an obligate bipedal? (What are the differences between bipedals and quadrupedals?)The foramen magnum is in the back of the head for “knuckle-walkers,” while it is under the skullfor humans/obligate bipeds. The shape of the spine is straight for chimps, yet for humans/obligate bipeds, it is S-shaped. The pelvis muscles are smaller for chimps and larger for humans. The knee is bent for chimps, yet for humans, it is an extend/lock knee. For chimps, their feet have no arch and have an opposable big toe. For humans, they have a pronounced arch in their foot. Why did bipedalism evolve?Bipedals are four times more efficient than chimps. Bipedality has a less energetic cost of walking than chimps’ knuckle-walking. The time of hominid evolution corresponds to a time of rapid climate change and a rapidly changing landscape. The last 25 million years correspond to atime of cooling temperatures, and the cost of locomotion for bipedals/humans is significantly less than for chimps/quadrupedals. This cooling of the climate corresponds to increased drying in Africa, fragmentation and reduction of forest and thus, an increase of savannah. This was a response to increasing areas of open savannah, so organisms must traverse the savannah in order to find food in rainforests. In crossing the savannah, the sun is beating down, increasing the organisms’ temperature and consequently, their body water loss. The bipedals have an edge in terms of heat loading: they receive more cook breeze and less heat radiating from the ground. Further, when the sun is directly above in the sky, it is hitting more surface area of the chimp than the human: In this image, the shadows cast by knuckle-walkers (top) and bipeds (bottom) prove this.Further, in persistence hunting (running and tracking until the prey falls from exhaustion), bipedals obviously have the advantage. This is because humans have a low heat load and they also have sweat glands.Was Lucy a modern human? Her jaws and teeth are less expansive than in humans. In terms of her jaw and skull, Lucy and some of her contemporaries were more chimp-like than modern human-like, even though they were bipedal. In comparison with other primates, the australopithecines had a bigger brain size both within primates and within the genus Homo. Further, at 2my, there is evidence to prove the brain capacity to be twice as much as before. This development of the hominid brain is also shown in changes of social and cultural behavior, where crushed bones (of animals they may have eaten) show the use of stone tools.In terms of biogeography, where did the members of the genus homo move? What are the hypotheses regarding this?The members of the genus homo move from Africa to Asia and Europe. Tools help with this relocation of the genus, and glaciers in the North and the deep South limit their movements and force them to develop other tools. Specifically, the species homo neanderthalensis (Neanderthals) evolved outside of Africa, near East Europe during the late Pleistocene. They have short bodies, yet are more robust. The Neanderthals were extinct around 30,000-40,000 years ago. Modern humans – homo sapiens – had their earliest appearance in Africa. They appeared around 200,000 years ago and are (obviously) still present today. We (modern humans) have a different shape in our skulls compared to Neanderthals. Further, there is evidence of changes in social/cultural behavior: cave art and deliberate burials. Lecture 20What are the two popular hypotheses regarding the relocation of the genus homo?Two popular hypotheses regarding the relocation of the genus homo are the Out of Africa hypothesis and the Multiregional Hypothesis. The Out of Africa hypothesis argues that every living human being is descended from a small group in Africa who then dispersed. The Multiregional Hypothesis claims that our earliest hominid ancestors radiated out from Africa and Homo sapiens evolved from several different groups of Homo erectus in several places throughout the world. Molecular data supports the Out of Africa hypothesis. What group represents the “missing link” between apes and humans? Australopithecines like Lucy.When do we find the first fossils of this group and where? About 3.2 million years ago, in Africa.Name two aspects of their skeletal morphology in which they differed from the great apes, but not from humans. The shape of the spine is straight for chimps, yet for humans/obligate bipeds, it is S-shaped. Thepelvis muscles are smaller for chimps