The transition between the Pliocene (5.3–2.6 million years ago) and the Pleistocene (2.6 million–11,700 years ago) has long been seen as a critical moment in human evolution. Researchers assumed this period marked a shift from wetter to much drier climates in North Africa, driving adaptations like bipedalism and tool use.
Now, the new data suggest a different narrative. Stable precipitation patterns may have dominated this critical interval, creating an environment where hominids could occupy diverse ecological niches without facing extreme droughts.
Notice the words “suggest a different narrative.” This research re-interprets previous physical findings (dust deposition) and does not deny the previous research that the Pliocene-Pleistocene transition had frequent, radical temperature fluctuations.
Archaeologists begin with hard evidence, such as soil cores and pollen grains. Then the fun part begins. The evidence can be interpreted in different ways. It often takes quite a while of back-and-forth controversy before the consensus of the experts moves to accept a particular story. In this case, whether the transition was dry, wet or fluctuating and how that influenced hominin survival over millions of years.
The dust reinterpretation comes about because this research adds a new paleo method utilizing hydrogen isotopes in leaf wax. From the paper:
“Our high-resolution leaf wax isotope record demonstrates remarkably consistent northwestern African summer monsoonal rainfall behavior across the Plio-Pleistocene boundary despite global cooling, climate events such as iNHG, and intensified 41- kyr glacial-interglacial cycles, standing in stark contrast to the body of dust flux records traditionally interpreted as a hydroclimate index.”