Mini-Exam2 Sp2020

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Evolution of Human Behavior (Psych397) Name: Samantha Powers Spring 2020 Mini-Exam 2 Essay/Discussion 1. Modern humans ( Homo sapiens ) have been around for about 200,000 years and it is estimated they left Africa at least 100,000 years ago. However, other human species had already left Africa before H. sapiens . Which species of the genus Homo was first found outside Africa and was also the longest-lived species in our family tree? (1 pts) This species was successful in adapting to different environments and travelling far. How far they went? What morphological characteristics have been described in this species that may have helped it become successful at dispersing and living for so long? (2 pts) How does this species play a part in the two hypotheses that try to explain how early humans migrated out of Africa? Explain these two hypotheses and the supporting evidence (4pts). Which hypothesis is currently more favored and why? (1 pts) What other species of Homo likely interbred with Homo sapiens and what do we know about them? (4pts). The species of the genus Homo that was first found outside Africa and was also the longest-lived species in our family tree were the Homo Erectus. This species was successful in adapting to different environments and traveling far. They traveled to Northern, Eastern, and Southern Africa, Western Asia (Dmanisi, Republic of Georgia, and East Asia (China and Indonesia). The morphological characteristics in this species prepared and helped them too develop successfully at dispersing and living longer. They also had reduced molars and premolars for Systematic hunting for they preyed on animals. They had a significantly larger brain and also had developed tools to use for hunting. This species played a part in the two hypotheses that try to explain how early humans migrated out of Africa. The first hypothesis states Homo sapiens evolved initially in one place in Africa, then migrated out of Africa and replaced all other species, then H. Erectus left Africa 700,000 years ago and became extinct. Evidence for this hypothesis is there is a strong correlation between geographical distance and genetic differences suggesting a single origin. The mtDNA of low variability among humans and greater difference between two gorillas living in the same forest is due to mtDNA being the most variable in Sub-Saharan African populations. This is evidence that they probable evolved here. The second hypothesis is that humans evolved in Africa and replaced H. erectus. The mtDNA data supporting this theory correlates with fossil records. There is also thought to have been two major radiations or waves. The first wave was modern humans left early and became ancestors of the Neanderthals that evolved in Euasia. The second wave was a small group of migrants left that were closely related to east Africans. This supports the fact that most non-Africans are descendent of the 2 nd wave. The hypothesis that is the most favored is the genetic and fossil evidence is the one suggests that homo sapiens emerged in Africa. Research supports the out of Africa theory due to the Neanderthals sharing more genetic variants with present-day humans in Eurasia than with present – day humans in sub-Saharan Africa. This stems from the multiple episodes of

interbreeding between the Neanderthal and modern humans. Another species of Homo that likely interbred with Homo sapiens were homo heidelbergensis. This species was found in Africa and Europe and shares similar features with h. erectus and h. sapiens like large brain cases, rounded skill, receding chin and forehead. When (roughly) did Australopithecines evolve, what anatomical characteristics were observed in them and what can we infer about their behavior? (4 pts) When did bipedalism evolved? Explain 4 hypotheses that try to explain the evolution of bipedalism and the evidence in support or against of them (8 pts). Australopithecines evolved roughly 4 million years ago. The anatomical Characteristics that were observed in them were they walked upright on a regular basis and also still climbed trees. The Anatomical changes that correlated with bipedality were the shape and proportions of the spine, the relationship of spine to head, shoulders and hips, the shape and size of hips, and the angle of upper leg relative to hip and ground. Bipedalism evolved 10-5 million years ago. The environment was cooler and dryer, there was a decline in tropical forests, increase in grassland, and a decline. This was when the rise of australopithecines came about. The first of four hypotheses that tried to explain the evolution of bipedalism was the “Man the hunter and toolmaker” Washburn’s logic for this hypothesis was evidence of fossil records, stone tools, freeing of the hands, and reduction of canines by using tools for hunting and defense. The problems with this hypothesis is the question of who made and used the tools, there being fossils of many species, there being some older then stone tools, and the fossil footprints being older then tools, making them question the accuracy. These factors brought doubts to this hypothesis, along with the australopithesine teeth molars being larger than expected for body size, suggesting more chewing/grinding of plant material had to have taken place do to molars being smaller when shifting to meat diet. Another hypothesis that try to explain the evolution of bipedalism is the savanna- based theory. This theory suggests that the early hominids were forced to adapt to an open savanna after they left the trees by walking erect on two feet. According to this theory, the evolution of bipedal locomotion would have been helpful in the savanna because the posture would allow hominins to watch over tall grasses, hunt effectively, or be aware of predators. There are arguments against the savanna-based theory, due to fossil record showing that the early bipedal hominines were still adapted to climbing trees as well. Several researches have indicated that bipedalism evolved in trees. Another hypothesis is the postural feeding hypotheses. This states that bipedal movements might have evolved into regular habits because they were convenient for obtaining food and keeping balance. It has been observed that chimps were only bipedal when they ate. Chimpanzees would reach up for fruit hanging from the trees, and orangutans used their hands to stabilize themselves, while navigating thinner branches (Stanford 2006). Australopithecus afarensis had hand and shoulder features that demonstrated hanging habits, whereas their hip and hind limb clearly indicated bipedalism. Because a bipedal posture was utilized for grabbing from an overhead branch and harvesting food, there are arguments that bipedalism evolved more as a feeding posture than as a walking posture. The last of prominent bipedalism theories is the provisioning model. This model demonstrated how hominins became more bipedal over the time not only by food gathering but also by provisioning infants (monogamy), but the provisioning model did not have

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