Being Pretty Isn’t Easy… Oh, Screw It!
… and it’s a matter of chance too, as it appears. Have you ever wondered why, if only the ‘sexiest’ genes survive selection, we don’t all look like Brad and Angelina? Besides the fact that the concept of sexual attractiveness is a culturally determined concept, it seems that scientists have found the answer lurking in mutations of our DNA repair kits.
This question, the ‘LEK PARADOX’ as it is called, has puzzled scientists for years. According to Darwin’s Theory of Evolution, sexually-selecting species such as humans should have much less variation than we do. If females select the most attractive males surely the ‘ugly’ gene should be wiped out by now? Sure there are secondary selection criteria as cars or bank account, and,
But, let’s face it, given the option between Ashton Kutcher and Danny DeVito..?
Looking around us, this expected scenario is far from the case; Professor Marion Petrie and Dr Gilbert Roberts of Newcastle University launched a new theory about biological reasons. Their research suggests that our ugliness, or should I say variation, is due to genetic mutations in our DNA repair kits (as the name suggests these are repair proteins which identify, bind to, and repair damaged DNA).
Less efficient repair kits results in greater genetic variation, as damaged DNA is un-repaired. The scientists’ research has shown that this phenomenon produces variation at a faster rate than sexual selection can get rid of it.
‘We started this research ten years ago and our model has now produced a good fit with what we observe in terms of genetic variation, which leads us to believe that our theory is correct’ says Professor Petrie. ‘We find that sexual selection can promote genetic diversity despite expectations to the contrary.’
While DNA mutations are generally found to be harmful, they can actually be useful in parts of the genome responsible for disease defence. Greater genetic variation in these areas can actually promote increased resistance to bacterial and viral attacks.
On top of this, previous research from Professor Petrie has actually shown that men with greater genetic diversity are actually found to be more attractive to women. So there you go – love your mutations!
Heredity. 2007 Apr;98(4):198-205. Epub 2006 Nov 22.
Sexual selection and the evolution of evolvability.
* Petrie M, Roberts G.
Evolution and Behaviour Research Group, School of Biology, University of Newcastle upon Tyne, Newcastle-upon-Tyne, UK.
Here we show that sexual selection can have an effect on the rate of mutation. We simulated the fate of a genetic modifier of the mutation rate in a sexual population with and without sexual selection (modelled using a female choice mechanism). Female choice for ‘good genes’ should reduce variability among male subjects, leaving insufficient differences to maintain female preferences. However, female choice can actually increase genetic variability by supporting a higher mutation rate in sexually selected traits. Increasing the mutation rate will be selected against because of the resulting decline in mean fitness. However, it also increases the probability of rare beneficial mutations arising, and mating skew caused by female preferences for male subjects carrying those beneficials with few deleterious mutations (‘good genes’) can lead to a mutation rate above that expected under natural selection. A choice of two male subjects was sufficient for there to be a twofold increase in the mutation rate as opposed to a decrease found under random mating.Heredity (2007) 98, 198-205. doi:10.1038/sj.hdy.6800921; published online 22 November 2006.
PMID: 17119550 [PubMed – in process]