Modern Marine Ecosystem in Place By Time Trilobite Fossils Appear

 This study made the case that the evolutionary rate of trilobites during the Cambrian wasn't all that extraordinary. Most naturalists look at that and say "See! The Cambrian Explosion wasn't all that explosive after all!" But if they do that they miss the fine print that makes their problem worse, not better. 

"We conclude that the Cambrian explosion was over by the time the typical Cambrian fossil record commences and reject an unfossilized Precambrian history for trilobites, solving a problem that had long troubled biologists since Darwin."

So they "solved a problem" about the Cambrian explosion by......saying the real explosion happened BEFORE the Cambrian trilobite fossils show up. Yet they also reject the idea that there was an unfossilized Precambrian history for trilobites. IOW, the explosion was over by the start of the typical fossil record, and there were none before that (in the Vendian).

"Our data therefore provide robust, quantitative evidence that by the time the typical Cambrian fossil record begins (∼521 Ma), the Cambrian explosion had already largely concluded. This suggests that a modern-style marine biosphere had rapidly emerged during the latest Ediacaran and earliest Cambrian (∼20 million years), followed by broad-scale evolutionary stasis throughout the remainder of the Cambrian."

I was glad they used the term "Cambrian explosion", as many science-deniers, of the naturalistic persuasion, have denied there was a true Cambrian explosion. Indeed the purpose of this study was to show that the Cambrian did not have excessively rapid rates of evolution- after the typical fossils of the period show up. But in so doing they are making what occurred before even more explosive!

They emphasize that trilobites did not have a pre-Cambrian history. Indeed one section of their report is "A Cambrian Origin for Trilobites". So somewhere between 541 million (edit, Wiki says 538.8 mya)  to 521 million years ago is when all of this change took place. By only looking at trilobites they are very much narrowing the scope of their problem because so many other forms show up too, including a host of trilobite-like creatures in addition to many other phyla. The oldest trace fossils of what can be described as euarthropods (a group which includes trilobites) are 537 million years old (last section). In other words, they show up at basically the same time everything else did (the Cambrian started 541 MYA). Indeed it apparently took only 410,000 years, a shockingly brief figure, for the Ediacaran biota to be replaced by Cambrian biota. This is made even more shocking compared to the very minimal evolutionary progress of the Ediacaran fauna. If evolution is universal, why didn't the Edicarans do much of it? The Cambrian biota showed much more diversification in their first eight million years (and likely much less) than their predecessors did in 80-100 million years. 

Saying that evolutionary rates were not much out of the norm for the Cambrian once typical (trilobite) fossils show up only solves the problem for the history of fossilization. It doesn't solve the problem of where this modern marine ecosystem came from, because it seems to be in place from the start, without reasonable ancestor forms. It would be like saying a billion dollars appeared in my bank account from nowhere but this is not unusual at all because after the billion dollars appeared my bank account behaved normally, changing with normal deposits and withdrawals. 

PS- there is an issue that defies naturalistic evolutionary expectations within the Cambrian, even if the overall rate isn't much out of the ordinary. The way things appear is strange. There are very few species per order (or sometimes "superfamily" depending on how they rate it). It is like things happened in the reverse of the description of evolution where a species over time becomes a group of closely related species called a genus. Then over more time one or more of those species gets so different than the rest that it becomes its own new genus. This in effect forms a new family that often contains many genera. Eventually that family may be so different from the original species, or other of its descendants, that it becomes a superfamily, or even a new order. But this isn't what we see in the Cambrian. New Orders show up without a lot of speciation. The leaps between form are bigger, even if there are fewer steps (species) between them. Saying that "speciation didn't occur at a fast rate during the bulk of the Cambrian" doesn't deal with this issue at all.

This study did not address how the evolution "started from the top" and went down rather than the standard bottom-up diversification we hear about. There isn't a lot of speciation going on, yet new types at higher taxonomic levels appear. Indeed simpler and more complex appear at the same time, defying naturalistic paradigms. But this isn't the only time that's happened in earth's history. It happened with tetrapods, it happened with comb-jellies, and it happened in the Ordovician. 

    You Tube Channel