Humans inarguably have the most impact on evolution. With constantly advancing technology, such as antibiotics, and the animals that we eat, we play an integral role in driving evolution.

University of Minnesota biologist Emilie C. Snell-Rood offers evidence that suggests that as we change the natural habitats of animals, we may be causing them to evolve with bigger brains.

Dr. Snell-Rood studied dozens of individual skulls, some as old as a century, from 10 species, including mice, shrews, bats, and gophers. The dimensions of the skulls were measured, allowing them to estimate the size of the brain.

The results yielded two significant results. In two species, the white-footed mouse and the meadow role, the brains of the animals from the cities or suburbs were about 6 percent bigger than the brains of the animals from farms or other rural areas. Dr. Snell-Rood concludes that their brains became significantly bigger when they moved to cities and towns. Animals in cities and town must learn to find food in places their ancestors never had to encounter.

An increase in brain size was also detected in two species of shrews and two species of bats found in rural Minnesota. Dr. Snell-Rood proposes that this occurred due to the radical change affected by humans in Minnesota. Cities and farms have taken the place of forests and prairies, disrupting the environment. As a result, the animals that were better at adapting to new things and were more likely to survive and breed.

Other studies support the idea that animals with bigger brains also learn better. Researches at Uppsala University in Sweden conducted an experiment in which they bred guppies for larger brain sizes. The big-brained fish scored better on learning tests than those with small brains.

"I think the results are exciting and deserving of much follow-up work," says Jason Munshi-South, an evolutionary biologist at Fordham University.

Follow-up research may include the breeding of small-brained rural mammals with big-brained mammals, in order to study the genes involved in producing different brain sizes. Further testing can also gauge how much human society has affected the way their brains work. 

Image by TJPainter, courtesy of Creative Commons licensing.