Lifestyle Evolving organisms found survival in sex

Evolving organisms found survival in sex

Being ‘lovesick’ takes on a whole new meaning in a new theory which answers the unsolved fundamental question: why do we have sex?

University of Adelaide researchers have developed a computer simulation model which supports the theory that sexual reproduction evolved because of the presence of disease-causing microbes and the need to constantly adapt to resist these ever-evolving bugs.

“Asexual reproduction, such as laying unfertilised eggs or budding off a piece of yourself, is a much simpler way of reproducing,” says Dr Jack da Silva, Senior Lecturer in the University of Adelaide’s School of Biological Sciences.

“It doesn’t require finding a mate, and the time and energy involved in that, nor the intricate and complicated genetics that come into play with sexual reproduction. It’s hard to understand why sex evolved at all.”

One theory says sex evolved because it allows the recombination of DNA between mating pairs so that individuals are produced that carry more than one beneficial mutation. However, Dr da Silva, says, this theory doesn’t explain why sexual reproduction would be maintained in a stable, well-adapted population.

Another evolutionary theory says that our pathogens, such as bacteria, viruses and parasites, are continuously adapting to us and we need to evolve constantly to become resistant to them. This provides the opportunity for new mutations to be beneficial and maintains a strong selective force.

Dr Jack da Silva and student James Galbraith have developed a new combined theory through computer simulations. Their model accurately reproduced the rapid evolutionary increase shown in the amount of sex with other individuals exhibited by nematode worms coevolving with a highly pathogenic bacterium.

“This is not a definitive test but it shows our model is consistent with the best experimental evidence that exists,” Dr da Silva says.

Read more about the origins of sex here. Story credit: University of Adelaide newsroom.

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