aidan k said:

“The man has a very interesting thesis - that the development of vision was the PRIME cause of the "Cambrian Explosion" in the diversity of Metazoan life in general and life-with-hard-parts in particular.
My gut feeling (as a professional geologist, bored out of my skull logging an oil well in the middle of the sea) is that he's got a significant part of the story, but not the only part. Vision in a predator species would certainly have had an effect, but there must have been other things happening at the same time - perhaps changes in ocean chemistry - that enabled or made easy other less-obviously correlated developments. In particular, the development of hard part through the Tommotian "small shell fauna" took a significant amount of time. Not a huge amount of time, one to several million years, but it's noticeably slower than the time scale the Parker implies vision might have developed in.
I suspect that more detailed work in the Vendian / Cambrian interface is going to show that yes, vision did develop rapidly in this time period. But yes also, hard parts were developing rapidly ; and plausibly (though hard to demonstrate from the fossils themselves) a behavioural Red Queen's Race of predator vs prey strategies would have been going on too.
Which of these major influences was the chicken and which was the egg isn't likely to be a question that is going to have a clear answer. Despite what Andrew Parker claims for his specialism.”

posted Sunday, October 28 2007