Monsoon rains in Asia are partly responsible for driving the evolution of mammals, a new study reveals.

An international team of researchers studied how evolution of bamboo rats, African mole rats and other species changed over time, and compared that to records of changing monsoon patterns. Rodents were selected for the study due to the fact that they are common in the fossil record, and the animals are greatly affected by the environment.

They found a correlation between the frequency of the weather systems and body features in the mammals, including the shape of the heads and teeth. The study covered records of 38 species lasting 24 million years. Of the animals examined, 32 are currently extinct, and some of these species may have been wiped out by monsoons, researchers report.

"It was natural to assume that a mighty climatic phenomenon like the monsoon would play a part in evolution, but until now there has never been any decisive evidence thereof. We have now found that," Fabien Knoll from The University of Manchester said.

During periods when there was little rain, teeth of the rodents changed, providing the animals with the ability to dig into the hard ground. Doing so would have helped protect the creatures from predators, in an environment with little vegetation to hide the prey animals.

Varying monsoon conditions could have also altered patterns of evolution in other animals, although changes in the body plans of other animals would be different from adaptations seen in rodents, researchers stated.

Monsoons are seasonal changes in the direction of prevailing winds in a given area. Although they can cause both wet and dry conditions, they are usually associated with torrential downpours, which can greatly alter conditions in an affected area. Summer monsoons can bring vast quantities of precipitation to areas near Bangladesh, Sri Lanka and India, between the months of April and September.

Agriculture in those nations is dependent on the water delivered by these weather systems. It is partly due to these monsoons that India is the world's top producer of dairy products. However, these heavy rains can also cause a great deal of damage to buildings and infrastructure, often taking human lives in the process. More than 100 people died in India during a monsoon that struck, before the storm delivered over 39 inches of rain to Maharashtra, killing over 1,000 people.  

This new research could help biologists protect animal species living in areas subject to the torrential downpours, investigators believe.

Analysis of the role of altering monsoon patterns on the evolution of rodents was profiled in the journal Scientific Reports.

Photo: McKay Savage | Flickr