The Evolution of Developmental Complexity

Has complexity increased during evolution? If so, has complexity evolved due to active or passive mechanisms? These are deceptively simple questions that have exercised biologists for decades.

We have developed a measure of the complexity of cell lineages based on Kolmogorov complexity (Azevedo et al. 2005) and have been using it to understand how development evolves. For more information on this work see the Cell-O website.

The Evolution of Developmental Variability

Phenotypic variability constitutes the raw material of evolution by natural selection. However, the levels of developmental variability have, themselves, evolved (Cunha et al 1999). For example, animals typically show cell number variabilities, as measured by the coefficient of variation, in the 5-25% range (Azevedo & Leroi 2000), but some animals have evolved very low levels of cell number variability. Why is that?

Nematodes provide good models for this problem because some species, such as the soil nematode C. elegans, develop through an invariant cell lineage, while others, such as the marine nematode Enoplus brevis, do not.