Stardate 20020429.1301

(Captain's log): I've been rereading Stephen Jay Gould's book Wonderful Life which discusses the results of a dramatic reinterpretation of the fossils of the Burgess Shale. This is probably the single most important fossil find in the world. The majority of fossils only preserve "hard parts", mainly bones and teeth and calcified shells. Very rarely conditions were such that traces of soft tissues would be preserved in conditions where dead bodies would not be destroyed by other processes. The Burgess Shale is one such, and the fossils it preserves come from the early part of the Cambrian, shortly after the Cambrian Explosion of large multicellular animals. There is an earlier set of fossils which were found in Australia, but the creatures found there don't seem to correspond to any modern groups and it's thought that it was an abortive experiment. However, the fossils found in the Burgess shale include ancestors of all modern animal groups and definitely represent part of the history of modern life.

What's odd about the Burgess Shale is that it also contains a huge number of truly strange creatures which appear to not be related either to other contemporary creatures or to anything modern. Some of the weird wonders were misidentified on initial investigation: Hallucigenia was originally reproduced as being completely unrelated to anything modern, but was later identified as being a clear member of a modern group. On the other hand, such creatures as Opabinia and Wiwaxia and Anomalocaris have been reconstructed with a high degree of certainty, and they're absolutely not related to anything known.

The point of Gould's book is to try to talk about how the anatomical variety in the Burgess shale is far greater than in any fauna studied ever since. For instance, all modern arthropods fall into only three groups with recognizable characteristics; they're all variations on one of three basic designs: insects and other uniramians, chelicerates, and crustaceans. Historically there was a fourth major group, now extinct: the trilobites. But in the Burgess Shale there several other arthropods which are completely unrelated to any of those four groups. Indeed, it's not completely clear whether some of them are even arthropods, though it's not obvious what else they might be.

So what became of them? Why did such variety die out? Gould says that it largely partakes of chance. What he says is that by studying the fossils they've left, there isn't any way to point to one creature and say, "This one's doomed" and a different one and say "This one will conquer the earth." He then takes a step I consider unjustified and claims that a hypothetical zoologist on the spot, studying living organisms, would equally not be able to pick the winners and losers.

He could be right, but there's insufficient evidence for his point of view. One reason is that even with the magnificent preservation of soft parts in the Burgess Shale, there is still much we can not learn. It is possible, for instance, to make some rather shrewd guesses about general lifestyle (where they lived, in general what they ate) but more complex behaviors are obviously not preserved. And we have no clues at all about reproductive behavior or about how the young developed, which is obviously a critical factor in survival of the species.

For example, Anomalocaris is by far the largest creature found in the Burgess Shale, and it is quite evidently a predator. But what of its young? All small creatures would have been prey for larger versions of others. By analogy, no-one and nothing messes with a full-grown Nile Crocodile (if they want to keep living) but the babies have to be protected by adult crocs to prevent them from being eaten. It's exceedingly unlikely that the Burgess arthropods engaged in any kind of parental rearing or protection, so just how did the young survive?

Likely there was some chance involved. A mutation in one species could well have produced a marked decrease in the survivability of another. For example, suppose that nothing alive then was capable of seeing the color red. Suppose that the eggs of some species were actually a rather bright red, because within the limits of existing vision it actually blended into the background quite well. Then assume some predator mutates and becomes able to see all those yummy red eggs to eat. Obviously the red-egg species is in big trouble. Irrespective of how big and powerful and impressive the adults of that species might be, it is probably doomed due to reproductive failure.

There's a deeper reason, and it is the thesis here. It's a natural switch from non-zero-sum to zero-sum competition. At the time of the Burgess Shale, that switch hadn't yet taken place, and in the non-zero-sum "Expansion" phase, things are more forgiving. Once you switch to the zero-sum "Competition" phase, creatures which were viable before cease to be, and will die out.

Which is what happens to products, too.