Scarce emergence of new species drove the decline of African megaherbivores, study suggests

A recent study suggests that the decline of African megaherbivores, such as elephants and hippopotamuses, was not due to their vulnerability to extinction, but rather their slow rate of speciation. Researchers from the National Museum of Natural Sciences, the National Research Center on Human Evolution, and the University of Alcalá analyzed 3,327 fossil records over 23 million years, considering factors like body mass, tooth crown height, and environmental changes.

Around 7.2 million years ago, Africa's climate started becoming drier, altering landscapes and vegetation. While both the emergence of new species and extinctions increased initially, the rate of new species emergence slowed significantly around 3.6 million years ago, while extinctions continued to rise. This led to a loss of diversity among large-bodied animals, which began long before humans could have hunted them.

Species like Deinotherium and Anthracotheriidae were affected. The study found that while smaller herbivores went extinct at a faster rate, their faster speciation rates allowed them to recover more quickly. Large megaherbivores, however, lost diversity at a much slower pace due to insufficient new species emergence. This imbalance was exacerbated by aridification, which favored smaller ungulates over megaherbivores.

The expansion of open habitats, increasing aridity, and declining ecosystem productivity over millions of years contributed to the widespread loss of these large herbivores, with human activity playing a secondary role.