RUNAWAY HANDICAP

Considering a runaway selection,

If poetry can generate affection,

Surely plumes of paradise entitle

Me to a mate intent upon requital?

My handicap’s an eloquence provoking

Offended neo-liberal fits of choking,

But when this stirs the ire of middle-management,

Amanda’s quick to join me in my banishment.

“In the 1930s, the geneticist R. A. Fisher developed Darwin’s theory of sexual selection with the idea of ‘runaway’ sexual selection. Fisher suggested that if a heritable mate preference – for example, the preference for a larger than average tail – becomes genetically correlated with the heritable trait itself – in this case the larger tail – then a positive feedback loop will arise so that tails will eventually become far longer than would otherwise have been expected. This runaway selection may account for such features as the remarkably elaborate plumage of birds of paradise or the extravagant court­ship displays of the lyre bird.

For many academics, the significance of sexual selection as an evolutionary force only became apparent in the late 1970s, when Amotz Zahavi introduced the ‘handicap principle’. This was further developed in his 1997 book of the same name, which had the provocative sub-title A Missing Piece of Darwin’s Puzzle. Zahavi had recognized that for a physical or behavioural trait suc­cessfully to attract a member of the opposite sex, it had to impose an actual cost on the bearer. In other words, it must constitute a potential handicap to the bearer’s own survival. Otherwise, the possession of such a trait could be faked, making it wholly unimpressive.

The peacock’s tail that adorns the cover of Zahavi’s book is the classic example. Its impressive size imposes an energy cost on the bearer and increases the risk of predation: the larger the tail, the more noticeable the bird, and the slower it will be at escaping from dangerous situations. Moreover, to possess an elaborate tail fan, the peacock has to maintain itself in a healthy condition; it has to be good at finding nutritious food and fighting parasites. So, in the parlance of sexual selection theory, a large and colourful peacock’s tail is a ‘reliable indicator’ of particular good genes, since without such genes the bearer of this tail would either have been preyed upon or else would not have been able to sustain its elaborate nature.”

From Steven Mithen ‘The Singing Neanderthals’ – page 177