The Timing of Development

Abstract

The question of whether it is possible to fit together the developmental and evolutionary explanations raises a number of difficulties. In a sense, it is possible to consider that the problems concerning the development of the individual have nothing to do with those related to the evolution of organisms over time (Wallace B, Can embryologists contribute to an understanding of evolutionary mechanisms? In: Bechtel W (ed) Integrating scientific disciplines: case studies from the life sciences. Springer. pp 149–163. Retrieved from http://link.springer.com/content/pdf/10.1007/978-94-010-9435-1_9.pdf, 1986). If one describes the development as the temporal trajectory of an individual from the zygote to adult, then the timescale of the individual development appears to be radically different from the evolutionary time scale. This chapter aims to show that the time dimension is an essential element to explain the proximal mechanism of development, and that it remains unspecified if not still largely ignored by biologists. I suggest that by focusing on the characters rather than on the “developmental stages”, developmental biology, while approaching evolution, nonetheless and paradoxically lost sight of the actual temporal dimension its process (Beer, G.R. (de) 1930. Embryology and evolution. Gloucestershire: Clarendon Press; Hamburger V, Hamilton HL, J Morphol 88(1):49–92, 1951). Therefore, consideration and characterization of the timing of development remain to be done: it requires to analyze its peculiarities and the way they have been, or may be apprehended. This focus on the developmental time will allow us to emphasize the importance of time for the explanation of the developmental process.