PIXABAY A long-held theory in evolutionary biology suggests that, when local ecosystems shift, organisms rapidly speciate, evolving traits that allow them to survive. But a study published last week (February 10) in Science suggests that, at least in horses, this was not the case.
"According to the classic view, horses would have evolved faster in when grasslands appeared, developing teeth that were more resistant to the stronger wear that comes with a grass-dominated diet,” said Juan Cantalapiedra, a paleontologist at the Museum für Naturkunde in Berlin, in a statement. “They [would have] also became bigger to more effectively digest this low-quality food, and as a strategy against predators in these new, open habitats."
Cantalapiedra and his colleagues used fossil records of horses to analyze changes in teeth and body size. Then, they computationally generated phylogenetic trees of 138 horse species (7 living and 131 extinct) over 18 million years. They discovered that rapid diversification appeared three times: the first burst occurred in North America between 15 and 18 million ...
