The Tangled Bank Theory

Michael Ghiselin developed this idea further in 1974 and made some telling analogies with economic trends. As Ghiselin put it, "In a saturated economy, it pays to diversify." Ghiselin suggested that most creatures compete with their brothers and sisters, so if everybody is a little different from their brothers and sisters, then more can survive. The fact that your parents thrived doing one thing means that it will probably pay to do something else because the local habitat might well be full already with your parents' friends or relatives doing their thing.

Graham Bell has called this the "tangled bank" theory, after the famous last paragraph of Charles Darwin's Origin of Species: "It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other and dependent upon each other in so complex a manner, have all been produced by laws acting around us."

Matt Ridley, The Red Queen: Sex and the Evolution of Human Nature (2003-05-01)

• evolution
• evolutionary theory