By DAVID DERBYSHIRE

Last updated at 17:43 11 September 2007

It has been cursed by every footballer, runner and tennis star forced to remain on the bench because of injury.

But according to a new study, the much maligned Achilles tendon turns out to have played a crucial role in human history.

Scientists say its evolution two to three million years ago allowed our ancestors to run and hunt for the first time.

That freed them from a lifetime of grubbing around for berries, insects and scavenged food – and helped give them the evolutionary edge over their ape cousins.

The findings come from a new computer model of Lucy – the oldest know human ancestor who lived 3.2 million years ago.

Lucy – or Australopithecus afarensis – was discovered in Ethiopia in 1974 and named after the Beatles song Lucy in the Sky with Diamonds.

Although she had many ape-like characteristics – including a protruding jaw and sloping forehead – her posture that was more human than chimp.

A team at Manchester University used a computer programme to create a virtual model of her skeleton and muscles – and then put it through its paces.

To their surprise they found that Lucy was able to walk upright as efficiently as modern people.

However, her lack of an Achilles tendon at the back of her legs meant she was unable to run, the British Association science festival in York was told.

Dr Bill Sellers, who led the study, said running was a crucial step in the evolution of ape-men to modern people. The appearance of the Achilles heel was a major milestone for our ancestors.

“Running changes your options – if you are a runner, hunting becomes possible,” he said. “You won't walk down your prey, but if you are an efficient long distance runner you might be bale to run down your prey.

“Muscles are attached to bones by tendons which are big springs that store energy. We can make a model without tendons and it turns out its rubbish – it can't go very fast and it uses an awful lot of food to get from A to B.

“You really can't run if you don't have an Achilles tendon.”

None of our closest living relatives – the chimpanzee, gorilla and orang utan – has an Achilles tendon. None are able to run.

Dr Sellers believes the tendon evolved before two million years ago. That was the time of Homo erectus – a tall agile human ancestor.

“I would be very surprised if the two million year old Homo erectus couldn't run because you look at the skeleton and it looks so much like a human, except for the head,” said Dr Sellers.

“If you look at the Lucy skeleton 3.5 million years ago, it doesn't look at all like a human. It has much shorter legs and longer arms and I think there's every chance Lucy can't run.

“If you can find evidence of an Achilles tendon, then that will be the point which tells you when we started to run properly and picked up those big spears and started chasing things around .”