Evolution: like any other science it is predictable

Abstract

Evolutionary biology rejoices in the diversity of life, but this comes at a cost: other than working in the common framework of neo-Darwinian evolution, specialists in, for example, diatoms and mammals have little to say to each other. Accordingly, their research tends to track the particularities and peculiarities of a given group and seldom enquires whether there are any wider or deeper sets of explanations. Here, I present evidence in support of the heterodox idea that evolution might look to a general theory that does more than serve as a tautology ('evolution explains evolution'). Specifically, I argue that far from its myriad of products being fortuitous and accidental, evolution is remarkably predictable. Thus, I urge a move away from the continuing obsession with Darwinian mechanisms, which are entirely uncontroversial. Rather, I emphasize why we should seek explanations for ubiquitous evolutionary convergence, as well as the emergence of complex integrated systems. At present, evolutionary theory seems to be akin to nineteenth-century physics, blissfully unaware of the imminent arrival of quantum mechanics and general relativity. Physics had its Newton, biology its Darwin: evolutionary biology now awaits its Einstein.

Figure 1.

Two ‘unexpected’ examples of convergent evolution. (a) Trackways from the Santo Domingo Formation (Late Triassic–Early Jurassic) of Argentina that are interpreted as representing the activities of some sort of theropodian avialian (‘bird’), and possibly convergent to other flying theropods. Centimetric scale bar. Picture courtesy of Ricardo Melchor (Universidad Nacional de la Pampea, Argentina). (b) A protistan convergence. The dinoflagellate Haplozoon praxillellae, an intestinal parasite of polychaete worms that has converged on a cestode-like bodyform, including attachment structures, strobilation and a hairy covering. Scale bar, 10 mm. Picture courtesy of Brian Leander (University of British Columbia).

Figure 2.

Another ‘unexpected’ example of convergent evolution. Carboxysomes of bacteria that are strikingly similar to the protein coats of viruses, but are independently evolved. Upper, transmission electron micrographs of carboxysomes in a cyanobacterium (Synechocystis). (a) Entire cell in the process of dividing, five polyhedral carboxysomes are visible. Scale bar, 200 nm; (b) individual carboxysome. Scale bar, 50 nm. Reproduced from fig. 1a,b in Kerfeld, C.A., Sawaya, M.R., Tanaka, S., Nguyen, C.V., Phillips, M., Beeby, M. & Yeates, T.O. 2005 Protein structures forming the shell of primitive bacterial organelles. Science 309, 936–938; with the permission of AAAS and the authors. (c) and (d) show the alternative models for the carboxysome shell. Each is based on a shell constructed of 740 hexameral units and 12 pentamers, and the two models (c,d) differ in terms of the orientation of the hexamers. Reproduced from fig. 3d in Tanaka, S., Kerfeld, C.A., Sawaya, M.R., Cai, F., Heinhorst, S., Cannon, G.C. & Yeates, T.O. 2008 Atomic-level models of the bacterial carboxysome shell. Science 319, 1083–1086; with the permission of AAAS and the authors.