A new research by paleontologists from the Spanish National Research Council reveals that climatic change and ecosystems have triggered the evolution of horses over the last 20 million years. They analyzed 140 different horse species, most of which are extinct, by studying their fossil history.
The research’s conclusions question a classic theory. This theory connects the evolutionary success of these mammals to those novel adaptations which occurred 18 million years ago in response to the spread of grasslands.
The current research has a completely different view. "Environmental changes would have produced a lot more fragmented, mosaic-type ecosystems, where populations of horses with similar demands and adaptations could have evolved isolated from one another, resulting in different species but with a similar appearance", says Manuel Hernández , one of the researchers.
This probably was possible only in ecosystems with a lot of biomass and energy. This is owed to the fact that very similar species which would otherwise have been in heavy competition, could survive.
Diversification accelerated twice again, in 11 and 4 million years ago. This gave raise to new horse species very fast. But these did not display dramatic differences in appearance, they conclude.