| The evolutionary events that allowed the rapid occurrence of metazoa are still enigmatic. The presumably oldest metazoan fossils are microscopic and occur just above 635 Ma, at the beginning of the Ediacaran period. Upon condition that the lack of macrofossils in the lower Ediacaran strata is real, the assumption of a sudden appearance of already complex, but still small animals that flourished during the first half of the Ediacaran is a reasonable option. Consequently, the emergence of the first macrofossils with metazoan affinity in mid Ediacaran strata would indicate a second leap in animal evolution. Here, these apparent leaps are explained in terms of a new concept of evolvability that is based on well definable developmental modules: A system based... |
