How reptilian Tyson really put the bite on Holyfield

Mike Tyson's jaws came together on Evander Holyfield's right ear with a force like a 20-kg weight falling on to it - twice as great as people normally exert when they bite.

And the jaw action of the former champion on Saturday night was less like a human than a reptile: "He was shearing and tearing, which is almost alligator-like", said Tom Korioth, a scientist who specialises in the biomechanics of biting. Usually when we bite with our incisors, or front teeth, the downward bite is matched by a slight bending of the jaw, creating a slight sideways tearing force. But Tyson's chomping motion had an excessive tearing action, making it remarkably violent.

Holyfield needed plastic surgery to replace a piece of cartilage torn from his ear by Tyson, who was disqualified after he bit his opponent's other ear. His prize money was withheld and he has been suspended pending more hearings.

Professor Korioth, of the University of Minnesota's School of Dentistry, Minneapolis, has studied of the way the jaw works and the forces involved. After watching a video of the Tyson-Holyfield fight he said: "Most of the ear is cartilage, and you need a lot of power to bite through it."

According to New Scientist magazine, tests by Prof Korioth on volunteers asked to bite on pressure pads for five seconds showed that normally the incisors exert a force equivalent to a 10-kg weight. He estimated that the force needed to sever a piece of the ear's cartilage would be roughly twice as great. The volunteers, though, were not behind on points at the start of the third round against an opponent who had previously beaten them for the world championship. However, even Tyson might find a worrying opponent in a human tested in 1985, whose teeth came together with a force like a 170-kg weight. If he is banned from boxing he should think a while before taking up alligator-wrestling (and ear-biting). The reptiles' jaws can exert a force equivalent to a weight of between 650 and 1,400kg - more than 300 times greater than what he managed.