High-temperature environments of human evolution in East Africa based on bond ordering in paleosol carbonates. Introduction East Africa is the home of fossil localities found in regions that experience extremely high temperatures. For so long, there were debates on whether regions like these had always been hot and dry; and there was a conclusion that suggested these regions were possibly cooler and constituted a savanna type ecosystem during the Pliocene and Pleistocene period. Researchers assumed that such a climate and environment change could have occurred due to a few major circumstances being the creation of the East African Rift system which consequently led to differential surface uplift, as well as remains of mammals and plants that suggested a more open habitat. While less has been identified in regards to the analogy, a hypothesis is tested to answer the question researchers decided to analyze the temperature history from the Turkana Basin, in northern Kenya, by applying the carbonate clumped isotope thermometer. Hypothesis: Past ecosystem temperatures of carbonate formation (Pliocene and Pleistocene) from the Turkana Basin were not cooler or more vegetated than it currently is, they were comparable to or even warmer than today’s environment.

Methods To test the hypothesis, carbonate nodules were collected to use as samples > 50 cm below the surface areas of soil horizons from paleosols and similarly; recent soils that had nodular, crack pendant morphologies were sampled as well (from April through October 2008 as well as during January 2009). Additionally, data from soil temperatures in tropical environments was compiled to have a better understanding of the differences between the soils found from undisturbed tropical forest habitats and the soils found in open and disturbed forests. For a better understanding of paleotemperature record, it is important to relate the soil temperatures to air temperatures. This is important as solar heating of the soil surface increases soil temperatures.

Results The tests suggested that the fossil soil carbonate sample was closely related to the recent soil carbonate that was collected, suggesting that the fossil carbonates were not recrystallized during burial.

Reflection: The presented research article tackles excellently the high temperatures experiences in East Africa, and more particularly in the Turkana Basin, a human evolution. The authors did a spectacular job collecting samples and analyzing data in different periods of times, and additionally it was well elaborated. Although it is a well-written article, it might not be easy to understand unless you have geology and/or anthropology knowledge; however on a positive note, it encourages the reader to do a bit more research and understand certain terms. Similarly, to understand the data collected, it would be suggested to understand the certain terms and what they each mean to this particular study; depending on who the audience would be, I would suggest explaining certain terminologies for a better understanding of the research that was done. While the data was sufficient and supported the research article, it was a bit challenges to go back and forth trying to figure out what they were saying, which brings back the fact that it would help readers who are not necessarily experienced in the field to have a better understanding if it was explained in simpler terms; however that depends on who they targeted as an audience. Although terms were challenging and it required further research, the content was consistent and well put together, and also the title was a good fit as it introduced immediately the audience to the research.