Evidence for a geologic trigger of the Cambrian explosion

[Dead_Parrot]

MADISON – The oceans teemed with life 600 million years ago, but the simple, soft-bodied creatures would have been hardly recognizable as the ancestors of nearly all animals on Earth today.

Then something happened. Over several tens of millions of years – a relative blink of an eye in geologic terms – a burst of evolution led to a flurry of diversification and increasing complexity, including the expansion of multicellular organisms and the appearance of the first shells and skeletons.

The results of this Cambrian explosion are well documented in the fossil record, but its cause – why and when it happened, and perhaps why nothing similar has happened since – has been a mystery.

New research shows that the answer may lie in a second geological curiosity – a dramatic boundary, known as the Great Unconformity, between ancient igneous and metamorphic rocks and younger sediments.

More: http://www.eurekalert.org/pub_releases/2012-04/uow-efa041612.php

Ah, the Cambrian. Making the '60s look sane and sober since - well, forever.

[HereSince1628]

1. Very fond of Opabinia, one of my all time favorite

beasts from the past. I used it and Anomalocaris for extending discussions on asic patterns in animal morphology.

A bilateral critter with an odd number of eyes (5) is just so very very cool for speculation

[longship]

2. Love-hate relationship with Simon Conway-Morris

His work on the Burgess Shale is certainly worthy of his fame, first brought to the public by Stephen J. Gould in Wonderful Life.

Unfortunately, Simon-Morris has some very flaky beliefs. Apparently he is a theist (no real problem there, so is biologist Kenneth Miller), but Simon takes his metaphysical beliefs to an extreme that I would not recommend, if I were a compatriot in his field. He interposed his religious beliefs into his science to a point that many biologists are frankly uncomfortable.

Here we get into the very knotty problem of demarcation. So far I don't know any scientist, or theist who has solved it. There is a line between science and non-science. But nobody has ever to state any criteria to that demarcation. One may as well be arguing about the number of angels who can dance on the head of a pin.

Religion and science are not non-overlapping magisteria, as Stephen J. Gould called it. Religion does interpose itself on science. It has been this way since science's birth in ancient Greece.

Sorry about the ramble here. I have been reading Dawkins' The Ancestor's Tale for about the third time and your post about the Cambrian triggered some loose neural connections.

[Odin2005]

4. I like his work on the evolutionary relationships of Cambrian critters.

He showed that many of them are primitive remembers of existing phyla, such as Anomalocarids being primitive Arthropods, he essentially demolished many of Gould's ideas about the Cambrian Explosion.

But I agree with you that his religiosity is annoying.

[eridani]

5. There really were chordates there

Gould was commenting on research that was far from fully developed.

[Odin2005]

8. Also, IMO he was biased towards exaggerating the strangeness of the critters.

[eridani]

9. But there were still more body plans than exist in evolutionalry lines today n/t

[eridani]

6. Intelligent rambles are fine, IMO

Though I take issue with the common triviallization of the angels on the head of a pin issue. It just so happens that this is one of humanity's most significant intellectual problems. It was solved by Newton and Leibnitz.

[longship]

7. Touchè

nt

[laconicsax]

3. "Explosion" is such a piss-poor term.