The fossilised teeth of ancient rodents suggest that their ancestors found a way to cross the South Atlantic Ocean to colonise South America.
Hesham Sallam, of Oxford University's Department of Earth Sciences, and colleagues report in this week's PNAS new evidence that shows that the ancestors of new world rodents, such as the Capybara, came over from Africa or Arabia in the late Eocene 40-34 millions years ago.
This means that the ancestors of the world's largest living rodent must have found a way to cross the South Atlantic which divided South America from Africa/Arabia at this time.
Rival theories had given Asia, via North America, as a possible origin for the rodent populations [Caviomorpha] that emerged in South America. But this new research shows that evidence from both the fossil and molecular data points to an African/Arabian origin.
Hesham tells us: 'The caviomorph colonisation of South America evidently occurred via a chance dispersal across the vast South Atlantic.'
'Future paleontological research in the late middle Eocene should not only help to further clarify the later stages of evolution of these rodents but also the evolution of other mammalian groups such as primates.'