A Fresh Look at Major Evolutionary Transitions

In 1995, the Hungarian theoretical evolutionary biologist Eörs Szathmáry, together with the British theoretical evolutionary biologist John Maynard Smith, published their theory of ‘major evolutionary transitions’ in biology. The emphasis was not on all the small genetic changes that occur in organisms from one generation to the next, but on certain major organisational changes that occur only occasionally. Examples they offered of such changes are the appearance of chromosomes in cells, the formation of eukaryotic cells, or the emergence of a society with language. At first glance, the theory of major evolutionary transitions appears to overlap with the O-theory. On closer inspection, however, there are significant differences. To illustrate these differences, this chapter contrasts the use of criteria for levels of organisation in both approaches.