A pair of researchers at Flinders University has found evidence that suggests modern kangaroos diversified due to grassland expansion, not drying during the Miocene, as previous studies have shown. In their paper published in the journal Science, Aidan Couzens and Gavin Prideaux describe their study of marsupial tooth specimens that date back 25 million years and what they found. P. David Polly with Indiana University wrote a Perspective piece on the work done by the pair in the same journal issue.