How Does Climate Affect Human Evolution

Human Evolution FA1302
8 December 2013
Did Climate Affect Human Evolution?
Climate and environmental change has played a vital role in Earth’s history, and the outcome of these changes has been anything but idle in the evolution of primates. These drastic transformations in the planet’s atmosphere have been the impetus of evolution among species and has sparked interest to geologist and paleoanthropologist for years, resulting in a number of hypothesis that “propose that climate-driven environmental changes during the past 7 million years were responsible for hominin speciation, the morphological shift to bipedality, enlarged cranial capacity, and behavioral adaptability” (Behrensmeyer 476). For this theory to be properly supported, the antecedent question that needs to be identified is, do species adapt to change?
Naturalist and geologist, Charles Darwin, supported this idea, stating “that living things adapt to a place- a habitat” (Joyce 1).
He expressed this theory through the idea that animals and various primates partake in the act of natural selection. In 1997, the National Science Foundation (NSF) supported Darwin’s theory by gathering a research team together and running a serious of studies that demonstrated “that animals can adapt to sudden changes in their environment with surprising speed” (Dybas, Chery 1). Researchers Frank Shaw and Ruth Shaw of the University of Minnesota, St. Paul, and F. Helen Rodd of the University of California used wild guppies from the West Indies island of Trinidad and found that “fish that were moved from a predator-infested pool to a pool with just one predator grew larger, lived longer and produced fewer but larger offspring. In the span of seven to 18 generations--between four and 11 years--they became more like the native guppies in the relatively predator-free environment” (Dybas, Chery
1).
Although studies such as the one above indicates that species do indeed adapt to different environments, there still lies the question of if climate and evolution correlate. Anthropologist Rick Potts challenged this question. For many years, Potts has been “pushing the idea that climate made us" and that “habitats kept changing because climates kept changing” (Joyce 1). For scientist to gain more knowledge and research on this idea, they need to get a fuller climate history in places where human ancestors lived. Which, in this case, would be in East Africa.
The pulsed climate variability hypothesis states that about every 20,000 years ago, “the region vacillated between very dry and very wet periods” (Ferro 1). These extreme changes may have played a vital role in driving human evolution and researchers like Rick Potts and Mark Maslin dig and gather sediments from East African lakes by drilling into lake bottoms and retrieving tubes of muck that contain millions of years of climate history; ranging from “the fossils of the plant pollen and the organisms that lived in the lakes that respond to climate, to the chemistry of the sediments that also can give us very detailed information about changes in temperature and precipitation” (Joyce 1). By collecting these tubes of muck, scientists can compare climate timelines to the fossil records of our ancestors to see how climate affected evolution. Mark Maslin, who mainly focused on the findings form an East African Rift Valley, compared all the lakes that were known to have existed in the East African area over the last 5 million years with climate and human evolution records. Maslin findings were that events such as when humans first migrated out of East Africa, all happened during the wetter periods found on the climate records. Major events in human history, including when humans first started to migrate out of East Africa, happened during wetter periods. It was found that the appearance of early Homo erectus correlates to when a number of deep freshwater lakes appeared. In a press statement, Maslin explained that our ancestors “had to deal with rapid switching from famine to feast—and back again." This, he says, was what drove the evolution of new species with bigger brains, and later forced them to migrate out of East Africa, moving down toward South Africa and north to Europe and Asia” (Ferro 1). By having these freshwater lakes that create lush vegetation, early humans would have been practically forced to migrate for the search of food water.
Evaluations on lake sediment made it clear that East African lakes did in fact play a major role in the explanation of why and when hominin species migrated out of East Africa but after much speculation, it seems as though “we may have to consider that climate was not always the underlying cause and that intrinsic social factors and interspecies competition may have play a significant role” (Ferro 1). Because findings show that “Homo erectus represented an 80 percent increase in brain size over previous species, at the same time that there was the greatest amount of water covering the region” but they also show that other periods of brain expansion occurred when these same areas were extremely dry, “suggesting that brain size increases were driven by aridity” (Ferro 1). Climate did contribute, if not was the main factor of why our ancestors migrated out of East Africa but climate can not be truly be identified as the underlying cause of evolution.

Works Cited
Behrensmeyer, Anna K. "Climate Change and Human Evolution." N.p., 9 Apr. 2012. Web.
Dybas, Cheryl L. "Research Areas." Nsf.gov. The National Science Foundation, 27 Mar. 1997. Web. 11 Dec. 2013.
Ferro, Shaunacy. "Did Ancient Climate Change Drive Human Evolution?" Popular Science. Popular Science, 16 Oct. 2013. Web. 11 Dec. 2013.
Joyce, Christopher. "Did Climate Change Drive Human Evolution?" NPR. NPR, 22 Mar. 2010. Web. 11 Dec. 2013.