The molecular genetics revolution has transformed evolutionary biology, but with rather more success in some areas than in others. About 70 years ago, in an essay predicting the future of biology, J. B. S. Haldane wrote that "our ideal is to establish a family tree of plants and animals", in which he included being able to state when in the past the common ancestors of extant species lived. Haldane suggested that this could be achieved by chemical methods, and he was right, even if his timescale was not: Haldane predicted that it would take thousands of years, whereas phylogenetics has already been the outstanding success story of molecular evolution. Haldane foresaw not only the charting of the evolutionary past, but also the prospect of finding evidence for the central mechanism of darwinian evolution, namely adaptive change. He looked forward to being able to ask "What inheritable variations... show any sign of being ... of advantage to their possessor?". In this respect, molecular data have, as yet, thrown up disappointingly few examples.
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