Research which shows how early humans varied their diet between seasons have proved to be an "incredible surprise" to a Bradford University professor.

A team of international scientists has revealed how early humans ate about 1.8 million years ago.

Julia Lee-Thorp, professor of archaeological sciences at the University of Bradford who was part of the team, said the full findings would appear in the November issue of the journal Science.

The team - which included researchers from the University of Colorado at Boulder, Texas A&M University and Ohio State University - found that the eating habits of an early human called Paranthropus robustus varied between the seasons and even years.

The researchers analysed the ratios of carbon in enamel from four fossil Paranthropus teeth found in South Africa to reveal their diet.

A team from the University of Utah used the laser ablation method to analyse the enamel.

The scientists believed that Paranthropus were vegetarians specialising in extremely hard plant food that required a lot of crushing.

Julia Lee-Thorp said: "Previously we had only a very averaged view about the diet of Paranthropus robustus. Our earlier carbon isotope work hinted that they were not specialist vegetarians, but gave no details.

"Now, by analysing tiny increments of fossil enamel, we can demonstrate that what they ate changed during the year."

The team of scientists have worked together on similar types of research over the years and the latest project has built on that foundation.

"The findings were an incredible surprise because we didn't expect to see so much variation in the diet.

"It shows that they adapted their diet perhaps to the different conditions - which was a little unexpected."

It is the first time this type of research has been done on the enamel from Paranthropus and the team are hoping that they can use the findings as the basis for future research into teeth which pre-date the period.

In future such research will be able to be conducted at the University of Bradford because it now has the technological capabilities needed to process enamel.

The professor said she was looking forward to the future research that could be done using these findings.

"I just find it amazing that we are using tooth enamel," she said.

"So look after your teeth - they will last for two million years!"

e-mail: sunita.bhatti@bradford.newsquest.co.uk