This picture is neither a coffee stain nor a bad tattoo, but rather a fossil from one of the most important places that evolutionary scientists study the emergence of complex life: the fossils of Burgess Shale in British Columbia.
Burgess Shale fossils date from the period of the Cambrian Explosion (525-505 million years ago), when “all of the sudden” (for evolutionary biologists) complex life — great diversification, eyes, body segments, circulatory systems, etc — emerged.
How was this possible? Back in the day, I thought that genetic mutation best explained the process of evolution. In this line of thinking, the Cambrian Explosion would have happened because somehow the environment favored the accidental incorrect copying of genes — a sort of “X-man” approach to evolutionary history.
However, evolutionary development (evo devo) scientists have chucked this idea. Instead, they emphasize two bigger factors that give rise to biological diversity: master “tool kit” genes and the role of “junk” DNA to switch a gene on or off. More on these later this week, but the bigger point is that the role of the master tool kit genes and the “switching” DNA drove not only the Cambrian Explosion, but also the diversification among mammals — like us.
Source(s): _Endless Forms Most Beautiful: the New Science of Evo Devo_, Sean Carroll, Norton, 2005.
