Why cloning could wipe out species

Cloning on a grand scale could spell the end of species as they become progressively nastier, warn researchers at the University of Sussex.

Evolutionary biologist Dr Joel Peck has produced a mathematical model that suggests that asexual reproduction -in which organisms are reproduced from a single parent without fertilisation - leads to antagonistic behaviour within species and, subsequently, population decline.

"For decades evolutionary biologists have wondered why sexual reproduction persists when asexual reproduction seems more efficient, " says Dr Peck. "Virtually all species that are now asexual - excluding microbes - were originally sexual. But we have also seen that these asexual organisms are prone to rapid extinction."

Another puzzle has been the role altruistic behaviour, by which one organism helps another at some cost to itself, plays in the evolution process. As Dr Peck explains: "In many species adults help each other, even though this may cause harm to themselves. An example is when a honeybee 'commits suicide' by stinging someone attacking its hive. The stinger is left in the attacker and the defending bee dies.

"My theory predicts that, if a species becomes asexual, then it will also become progressively nastier so that helpful behaviour almost never occurs. Eventually, this sort of social degeneration can lead to the extinction of the species."

Dr Peck used computer simulation to follow the evolution of hypothetical populations of sexual and asexual organisms for 10,000 generations. The simulations take account of habitat, migration and reproduction. The results showed that, under some conditions, especially when a natural habitat goes into decline, members of sexual populations were three times more likely to survive to reproductive age than asexual populations.

As Dr Peck says: "In sexual organisms, when the going gets tough, the nice get going - they spread out throughout the environment. These nice sorts of individuals then hang around, even after environmental conditions improve. However, under asexuality, niceness doesn't have a chance. The most selfish types seem to take over in an evolutionary blink of an eye."

He adds: "If humans became an asexual population, then it seems very likely that we would quickly wipe ourselves out through sheer antagonism."

Dr. Peck's computer simulations allow for complex interactions between genes. This is something that has not been represented in computer simulations before even though such interactions are common in nature.

His research was supported by a £39,768 grant from the Biotechnology and Biological Sciences Research Council. His paper, Sex Causes Altruism. Altruism Causes Sex. Maybe, is published in the May 22 edition of the Proceedings of the Royal Society.

University of Sussex. April 2004.