Friday, 11 November 2011

Whiskers Were A Vital Step In The Evolution From Reptiles To Mammals

An artist's impression of Morganucodon, an early mammal
Whiskers are one of the more unusual features of many mammals. They are possessed by both the marine, such as the manatee, and the terrestrial, such as the common rat. The structures are composed of keratin and form a major part of the animal's sensory system. The base of each whisker is connected to a series of very sensitive nerves. The structure acts like a radar, picking up and amplifying signals, which the nerves send back to the brain. As a result, animals with whiskers can detect tiny vibrations or changes in current.

Now a team from the University of Sheffield, led by Professor Tony Prescott, believe that the appearance of whiskers was a vital step in the evolution of mammals from reptiles. Many small mammals move their whiskers back and forth at high speeds in a behaviour known as whisking. They use this to determine the position, shape and texture of objects, allowing them to build up a very accurate map of the environment around them. As many mammals which possess whiskers have poor eyesight, this extra sense is a great asset.

Yet why evolve such a feature in the first place? The first mammals were nocturnal and dwelt in the trees, out of the reach of amphibian and reptilian predators. The team suggest that whiskers evolved to aid sensory awareness because of poor light. We cannot be sure as to how good these first mammals' vision was, but it is likely that they too had poor eyesight.

Professor Tony Prescott said 'this latest research suggests that alongside becoming warm-blooded, giving birth to live young, and having an enlarged brain, the emergence of a new tactile sense based on moveable facial whiskers was an important step along the evolutionary path to modern mammals. Although humans no longer have moveable whiskers they were a critical feature of our early mammalian ancestors.'