The Why of Sex

Research is showing that sex confers significant evolutionary advantages on species.
Researchers have found that asexual population tend to accumulate harmful mutations and were not as well adapted to their surroundings as sexual populations of roundworms (Photo: ISTOCK)

There is a biological cost to sex, as should be evident to us from our own experience. Would things not be so much simpler if each of us could reproduce asexually, saving ourselves the emotional entanglements that take up so much of our being? After all, species which reproduce asexually, and there are many where every individual can give rise to an offspring, should be able to reproduce twice as fast as sexual species, where males cannot give birth.

It has long been speculated that sex confers an advantage by increasing the genetic variability of a species because each offspring (bar identical twins) is a unique mixture of the paternal and maternal genes. In species that reproduce asexually, the offspring is an almost exact copy of its parent, and for one is equally susceptible to disease—thus, say, when an infection sweeps through such a population, it takes a much heavier toll than it does in a more genetically varied population.

The other possibility put forth is that harmful mutations that take place at random tend to accumulate in asexual species while sex breeds them out. This, for example, would be one reason why sex among close relatives is counterproductive.

Now research by University of Oregon biology professor Patrick C. Phillips and his students shows that there is something to both these views. The researchers, working with roundworms, a species that propagates both sexually and asexually, genetically manipulated the worms into two separate populations, one sexual and the other asexual.

Tracking several such collections of the worms over 50 generations, they found that the asexual populations tended to accumulate harmful mutations and were not as well adapted to their surroundings as the sexual populations.

Science Buzz 31 Oct 2009 - 6 Nov 2009
  • Message in the Toilet

    According to a study by the London School of Hygiene & Tropical Medicine, only 32 per cent of men washed their hands with soap while 64 per cent of women did. A quarter of a million people were counted using the toilets and their use of soap was monitored by on-line sensors. Messages, ranging from ‘Water doesn’t kill germs, soap does’ to ‘Don’t be a dirty soap dodger’, were flashed onto LED screens at the entrance of the toilets and the effects of the messages on behaviour were measured. While women responded better to reminders, men tended to react best to messages that invoked disgust, for example ‘Soap it off or eat it later’.

  • Turning Male Flies into Lusty Lotharios

    When Professor Joel Levine’s team eliminated a class of pheromones—cuticular hydrocarbon pheromones—in fruit flies, at the University of Toronto Mississauga, they found that female fruit flies bred without the hydrocarbons were so sexy that even males of other fruit fly species courted them. The tweaked males were also sexually irresistible. The study, published in Nature, points to a link between sex, species recognition and a specific chemical mechanism. Levine stresses that while pheromones are part of the human mating dance, the cues for attraction are far more complex in our species.

  • Tiny Dino Species Identified

    A new species of dinosaur has been identified 30 years after its fossilised remains were discovered. Fruitadens Haagarorum, researchers say, is one of the smallest dinosaurs known to science. In the Royal Society journal Proceedings B, the researchers say that the dinosaur weighed less than 1 kg. It was agile and a fast runner, and lived about 150 million years ago. It belonged to a group of dinosaurs called the ornithischians—largely plant-eating creatures. The genus name Fruitadens refers to the area of Fruita in Colorado, where the fossils were first discovered.