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Spurred into action by the demands of politicians and the ordinary homo sapiens on the street, biologists held a meeting last week to sort out the question of what exactly constitutes a species.

They have been bickering about the problem for 200 years, according to Michael Claridge, professor of entomology at the University of Wales, ever since Linneaus started classifying plants. But arguments have intensified recently because the world is trying to stop its species going extinct and tends to assume that biologists will be able to pronounce on what species are.

Professor Claridge persuaded the many species of biologist around the world - ranging from virologists to primatologists - to gather at the University of Wales and sort themselves out.

"There's an enormous amount of controversy about it," he said. The problem is that some biologists think two groups of organisms are separate species if they do not interbreed (the biological definition); but others are more finicky and think that within a biological species, any group of organisms which all display a feature that is not present in all the others (such as a patch of colour) deserve the title of a separate species even if they could interbreed with the other organisms.

Meanwhile, there are plenty of organisms that do not breed sexually at all. Throwing DNA testing at the problem does not necessarily help, says Professor Claridge. Defining species by the amount by which their DNA differs would put humans in the same species as chimpanzees but put apparently identical marine algae into different species.

Professor Claridge is hoping eventually for a grand synthesis, "a general species concept with more specialist approaches for particular areas". Did the conference achieve this? Not exactly. "I believe that the difference between us is not as great as some people felt," he said.