Simpson, C. and Erwin, D.H., 2014. Enriching macroevolution. Science. 344(6189): 1234-1235. pdf
Review of Homology, Genes, and Evolutionary Innovation Günter P. Wagner Princeton University Press, 2014. 494 pp
What drives evolutionary innovation? This question has become a central focus of evolutionary biologists over the past decade as comparative evolutionary developmental biology (“evo-devo”) has established a mechanistic basis for understanding the evolution of form and, increasingly, the evolution of developmental processes themselves. The challenge has been to build a conceptual framework that makes sense of the facts of development and explains how development can evolve while producing viable offspring. Prior to the codification of evo-devo, heterochrony was invoked for this purpose (1). Heterochrony produces new phenotypes by varying the rates of somatic and reproductive maturation, and for a time it was a promising conceptual organizer of develop- mental evolution. But heterochrony can only modify existing allometric variation and thus cannot explain the origin of novel traits—and the history of life is strung with novel traits.