From Harry Pettit at the Daily Mail:
The ‘Cambrian explosion’ is one of the most significant events in the planet’s 4.5-billion-year history and ultimately led to the arrival of complex animals like humans.
New research shows the event – which took place between 500 and 540 million years ago – was a much more gradual process than first thought. More.
A team based at Oxford University Museum of Natural History and the University of Lausanne carried out the most comprehensive analysis ever made of early fossil euarthropods from every different possible type of fossil preservation. In an article published today in the Proceedings of the National Academy of Sciences they show that, taken together, the total fossil record shows a gradual radiation of euarthropods during the early Cambrian, 540-500 million years ago.
The new analysis presents a challenge to the two major competing hypotheses about early animal evolution. The first of these suggests a slow, gradual evolution of euarthropods starting 650-600 million years ago, which had been consistent with earlier molecular dating estimates of their origin. The other hypothesis claims the nearly instantaneous appearance of euarthropods 540 million years ago because of highly elevated rates of evolution.
The new research suggests a middle-ground between these two hypotheses, with the origin of euarthropods no earlier than 550 million years ago, corresponding with more recent molecular dating estimates, and with the subsequent diversification taking place over the next 40 million years.
“Each of the major types of fossil evidence has its limitation and they are incomplete in different ways, but when taken together they are mutually illuminating and allow a coherent picture to emerge of the origin and radiation of the euarthropods during the lower to middle Cambrian,” explains Professor Allison Daley, who carried out the work at Oxford University Museum of Natural History and at the University of Lausanne. “This indicates that the Cambrian Explosion, rather than being a sudden event, unfolded gradually over the ~40 million years of the lower to middle Cambrian.” …
Hmmm. Did very many people think that the Cambrian explosion was literally sudden, as opposed to a very swift development (40 million years) in terms of geological time? One thinks, for example, of an explosion of new ideas that in fact take decades to become entrenched in a population. They are an explosion compared to millennia of the old ideas, though not compared to a firecracker. Similarly, the Cambrian was an explosion compared to the Boring Billion.
Still no word on why everything sped up dramatically at that point.
See also: Maverick theory: Cambrian animals remade the environmentby generating oxygen
Michael Medved discusses intelligent design theory with Darwin’s Doubt author Steve Meyer
Hat tip: Ken Francis