Deocampo, Rabideaux examine the environmental conditions that coincide with early human evolution
Human evolution isn’t simply a matter of biology; the climatic and environmental conditions early humans faced also played a role in how our species developed. “It is broadly accepted that environmental change plays a role in evolution, but the extent to which it has influenced human evolution is still up for debate,” says Nathan Rabideaux, who recently completed his Ph.D. in Geosciences. Rabideaux, working with Associate Dean Dr. Dan Deocampo, helped uncover details about environmental changes that happened at Kenya’s Lake Magadi about half a million years ago, around the same time Middle Stone Age humans made some major advances in their technologies.
Rabideaux, Deocampo and an international team of researchers used drill core samples from the lake, with sediments dating back to 1 million years ago to learn more about the relationship between environment and evolution. Rabideaux and Deocampo’s analysis showed that the lake was freshwater 1 million years ago and has grown more and more saline (salty) over time. “This indicates that the environments around Lake Magadi became increasingly more arid beginning about 500,000 years ago and experienced intense drying about 350,000 years ago,” Rabideaux says. “This long-term drying trend is overprinted by pronounced wet-dry cycles that indicates a more variable climate regime in the region beginning around 350,000 years ago.”
The findings excite Rabideaux on multiple levels: While he is a geologist by training, he came into the field because of a fascination with the interaction between human evolution and climate change. This research, which was published in the Proceedings of the National Academy of Sciences in October, helps forward our understanding in that arena.
“What is intriguing about the timing of these events is that human ancestors were starting to develop more complex Middle Stone Age toolkits around this time,” Rabideaux says. “The timing also coincides with the emergence of early Homo sapiens and large diasporas of hominins out of Africa around 500,000 to 300,000 years ago. This research supports the hypothesis that high frequency environmental fluctuations act a forcing mechanism in driving vertebrate evolution, including hominins.” Furthermore, this research indicates that environmental factors might have influenced hominin behavior, and could even have promoted cultural exchange that advanced stone tool technology and social structures.
Since completing the research and his Ph.D., Rabideaux has headed to Rutger University’s Newark, NJ, campus, where he is a research analyst managing the X-ray diffraction and scanning electron microscope labs. “My job includes the operation and maintenance of the instruments, training and supervising students and faculty in use of instruments, and assisting faculty and students with research and teaching,” Rabideaux says. “My background as the XRD Lab Manager at GSU and experience using SEM in my dissertation research were instrumental in qualifying me for this position — I definitely wouldn’t be here if not for the knowledge and skills I acquired during my time in the Department of Geosciences at Georgia State University.”