A future with giant rats?

Source: scientias.nl
The future belongs to the rats. University of Leicester researchers predict that, because rats adapt so well to so many locations in the world, they could even evolve to giant-sized. They fill up the spaces left in ecosystems by animals that become extinct.
As a species, rats have benefited greatly from humans. We have helped them spread all over the world, and they have adapted successfully to their new environments. Rats live on many – if not all – islands around the globe, and are difficult to exterminate. They compete with native species and often come out on top, sometimes resulting in extinction for native species. The empty ecosystem niche left behind is then taken up by the rats, and when the animals are used to their new role, evolutionary adaptations can occur. According to the Leicester researchers, this can be compared with species sharing the earth with dinosaurs. Although there were mammals during the Cretaceous period, they remained small. Once the dinosaurs were gone, however, these mammals evolved; some even became as large as mammoths and horses. Scientists expect that rats could easily evolve to be the size of capybaras, the largest (80 kg) living rodents. If there were enough space in the ecosystem, researchers reason, rats could become even larger.

The investigators do indicate that it is difficult to predict exactly how rats will develop. That development depends on many factors, and those factors likely vary among ecosystems. Each island, then, can be seen as a laboratory for future evolution. Fat rats, thin rats, fast rats, slow rats, ferocious rats and water rats are among the possibilities. Perhaps our descendants will someday be amazed at the great diversity among the successors of the common rat.