In a paper published in Proceedings of the National Academy of Sciences (PNAS) this week Dr. Kaboth-Bahr and an international group of multidisciplinary collaborators identified ancient El Niño-like weather patterns as the drivers of major climate changes in Africa. This allowed the group to re-evaluate the existing thought regarding climate impacts on human evolution.
Dr. Kaboth-Bahr and her colleagues integrated 11 climate archives from all across Africa covering the past 620 thousand years to generate a comprehensive picture of when and where wet or dry conditions prevailed over the continent. “We were surprised to find a distinct climatic east-west ‘seesaw’ a lot like the pattern produced by the weather phenomena of El Niño, that today profoundly influences precipitation distribution in Africa,” explains Dr. Kaboth-Bahr, who led the study.
Wet and dry regions shifted between the east and west of the African continent on timescales of approximately 100,000 years, with each of the climatic shifts being accompanied by major turnovers in flora (plant-life) and mammal fauna (animal-life).
“This alternation between dry and wet periods appeared to have governed the dispersion and evolution of vegetation as well as mammals in eastern and western Africa,” explains Dr. Kaboth-Bahr. “The resultant environmental patchwork was likely to have been a critical component of human evolution and early demography as well.”
The scientists’ work suggests that a seesaw-like pattern of rainfall alternating between eastern and western Africa probably had the effect of creating critically important ecotonal regions — the buffer zones between different ecological zones, such grassland and forest.
“Ecotones“provided diverse, resource-rich and stable environmental settings thought to have been important to early modern humans,” adds Dr. Kaboth-Bahr. “They certainly seem to have been important to other faunal communities.”
“Re-evaluating these patterns of stasis, change and extinction through a new climatic framework will yield new insights into the deep human past,” says Dr. Kaboth Bahr. “This does not mean that people were helpless in the face of climatic changes, but shifting habitat availability would certainly have impacted patterns of demography, and ultimately the genetic exchanges that underpin human evolution.”
Or as I like to say…”Weather is everything”.