Are We Toys?

It’s not easy to make a new kind of organism. The rewiring and reconfiguration of embryonic development and physiological function as a consequence of long periods of evolution, referred to as “developmental system drift,” makes it unlikely that we can discern the kinds of “genotype to phenotype” maps necessary to rationally redesign the features of present-day organisms (a dream of genetic engineering and the new field of synthetic biology), without incurring unexpected outcomes. This conclusion has been confirmed in many experiments.

The basis of this degradation of genetic determinism is clear. Ever since animals and plants first appeared in the biosphere (estimated at more than 600 million years ago for the former, and 500 million years ago for the latter), there has been an enormous amount of additional genetic change, sometimes associated with the evolution of new biological features, but frequently reinforcing existing ones. These mostly random changes could occur along different “pathways” in genealogically related lines of descent, meaning that shared body forms and common anatomical structures often develop by utilizing different genetic circuitry. The segmented backbones of a zebrafish and a mouse, for example, are produced using gene sets that are only partly overlapping, and the gene overlap is even less for the generation of identical-looking digestive systems and reproductive organs in different species (even within the same genus) of nematode worms.

When we focus instead on the more pristine multicellular systems that gave rise to the first animals, however, a very different and rather unnerving picture emerges of how a few specific gene modifications led to dramatic and surprisingly comprehensible changes in the resulting biology. We know about the ancient history of the animals not only from the fossil record, but by way of the same DNA sequencing and “informatics” (i.e., computational) techniques that have —> Read More