After suggesting the existence of an evolution tool kit, how would one go about identifying the contents of such a tool kit? We would need to assign the functional role of ‘evolution’ to specific genes. Typically, biologists classify genes according to their functional roles. But they don’t assign evolution itself as a functional role.

Perhaps this is because a non-teleological viewpoint does not see evolution as a biological function, but instead views it as an unintended side product of reproduction and other biological functions. Or perhaps it is because such functional roles are determined in the lab using genetic and biochemical assays. Such tests can help us determine, for example, whether a gene is involved in protein folding and stabilization or the transport of anions. Yet because evolution is a process that occurs over great spans of time, such assays cannot detect a bona fide ‘evolution’ gene. It would be like trying to detect the arrangement of organs in a body by using a microscope.

If evolution is a process that occurs through deep time, any evolution gene would require a secondary function that allowed it to be maintained generation to generation. This would mean evolution genes will be biochemically and genetically detected through their secondary functions. In other words, when Sean Carroll identifies a took kit of developmental genes, might he really be detecting a tool kit of evolution genes? Not quite, as the developmental took kit genes simply turn on switches. As evo-devo shows, it is the switches, and not the developmental tool kit genes, that evolve (the tool kit genes typically show strong conservation over deep time).

Of course, this all points us in the direction of the evolution genes. We’ll consider our first candidate in the next installment.

In his book Endless Forms Most Beautiful, Sean Carroll explains the role of tool kit genes in the development of organisms. Tool kit genes express products that in turn regulate whether or not other genes are turned on during embryological development. As such, most of them are transcription factors that bind to regulatory regions of a gene, regions Carroll refers to as switches. What thus determines whether or not a particular gene is expressed during development is the combination of activated and repressed switches as a consequence of the composition of the tool kit gene products available.

The teleological echo of all this can be seen from more than one angle.

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