Re: Musings about the Cambrian Explosion


Tim Tyler wrote:
> Jim McGinn <jimmcginn@xxxxxxxxx> wrote or quoted:
>
> > You are dead right. The Cambrian explosion has to do with the fact
> > that the atmosphere, as a result of sea life, was beginning to be more
> > amenable to life which allowed lifeforms to survive on land and,
> > consequently, there was a relatively rapid (in geologic terms) increase
> > in viable space for lifeforms to survive.
>
> That sounds pretty unlikely to me. Most of the Cambrian explosion that
> we can see is an underwater phenomenon:
>
> ``Cambrian land-life is almost unknown in the fossil record.''
>
> - http://www.fossilmall.com/Cambrian_Shadows/Protichnites.htm
>
> Until now, most life has been underwater anyway. What happens on the land
> is just the tip of the iceberg.

Interesting. Well, maybe I'm wrong on this. I was
just trying to make sense of why there was such large
jump in the rate of novelty. The only thing that
makes sense is that there was a relatively sudden
increase in the spatially defined level of
opportunity. How about this. Maybe Oxygen breathing
lifeforms did not make it up to land during the
Cambrian (they would have to wait until there was
enough Ozone in the upper atmosphere to reduce
ultra-violate rays, possibly). But some ultra-violate
resistant plants did begin to colonize the land
surface. This produced a relatively sudden increase
in the amount of amount of oxygen from the CO2
breathing plants and this sudden increase in oxygen
is what afforded the cambrian explosion to
aquatic animals. (One way to test this hypothesis
is that we'd expect a relatively large increase in
species that breath directly from the atmosphere
rather than from gills, possibly? I don't know.)

Jim


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