The Cambrian Problem

The title of the first DpSU of the week is Is the Cambrian Explosion Problem Solved? You may be forgiven for being unaware that there was a C.E.P. – there isn’t, at least in the form that the creationists present it.

A pre-cambrian organism

What’s the problem according to Mr Thomas?

Evolutionists, starting with Charles Darwin, have had a difficult time explaining why such richly diverse aquatic life forms appeared so suddenly and with no trace of evolutionary ancestry in lower (pre-Cambrian) rocks. According to neo-Darwinism, new life forms develop through time, chance, and death. Without the time, the formula cannot work, and yet Cambrian fossils are a parade of well-designed creatures that lived at the same time, not in separate evolutionary ages.

This is…incorrect. For one, we’re talking tens of millions of years. Quite a lot of stuff happened during that time, it seems – although we have the problem that while finding a fossil at a particular point means that the organism existed then, with a much smaller number of finds to play with than we have for more recent periods, we can’t tell that it arose then and not earlier.

This problem is what some scientists term the “Cambrian Conundrum,” and researchers recently made another attempt to solve it. But their scenario, published in the journal Science, is a series of unfounded ad hoc stories coated with a scientific-sounding façade.

I should co-opt that definition for creation science… The paper we’re talking about is called The Cambrian Conundrum: Early Divergence and Later Ecological Success in the Early History of Animals – they propose that the various phylae that are attributed to the Cambrian explosion actually arose much sooner, but only became successful much later. It’s similar to how the mammals only really got going after the dinosaurs disappeared.

The standard tale is that Cambrian creatures did not evolve until about 500 million years ago. In contrast, these authors suggested that animals were actually alive and evolving 800 million years ago. But without the fossils to support their story, why should other scientists believe it?

Their answer was to ignore the fossils and emphasize molecular clocks. When the idea of a molecular clock was first conceived, researchers believed that DNA bases change at a steady rate over time, and thus “tick” at a reliable rate.

However, a decade of abundant research has clearly shown that DNA base change rates are not steady at all, and they are restricted to mutational “hot spots” and non-lethal changes that are different for various genes. For these reasons, and because most molecular clock-based evolutionary histories are markedly different from fossil-based ones, researchers routinely “calibrate” molecular clocks to fossils of supposedly “known ages.” The molecular clock estimates in this Science study were adjusted to 24 fossil-based “ages.”

He gives two cites for his “known ages” sentence, to two old DpSUs. This kind of calibration is important as, if we know a date from, say, radiocarbon dating, we get better results as they will be more accurate.

Thus tuned, the researchers’ clocks indicated that “the last common ancestor of all living animals arose nearly 800 Ma [million years ago].” This falls within the range reported by Stony Brook University’s Barry Levinson, who wrote in BioScience in 2008 that the molecular-based histories constantly contradict the fossil-based histories of life on earth.

From what I can see, he wrote that the kind of thing that these researchers found is pretty standard when it comes to people doing that kind of test, not that “molecular-based histories constantly contradict the fossil-based histories of life on earth.” He’s been quote mined without being quoted.

But if this molecule-based age of 800 million years is true, then how did animals avoid fossilization for 300 million years?

It’s possible that they did not develop the structures required, or, as these researchers are suggesting, they weren’t successful enough to appear.

The Science authors dismissed this problem and wrote that “teasing apart the mechanisms underlying the Cambrian explosion requires disentangling evolutionary origins from geological first appearances, and the only way to separate the two is to use a molecular clock.” In other words, they asserted that molecular clock procedures, though known to be unreliable, provide the real evolutionary history, not fossils.

They’re only unreliable in the minds of creationists – if researchers consistently get the same range of dates in this kind of study, that makes it reliable. The real question is accuracy, which is a completely different kettle of fish. The reason why they are better, as I said, is that there is no guarantee that organisms will fossilise, but evidence will be preserved in the genome.

The fact that these authors calibrated their “clock” to fossil age assignments proves that their clock was just as unreliable as prior clocks. It relied on the very fossil ages that their attempted solution to the Cambrian Conundrum tried to avoid! They can’t have it both ways, and they should not have cherry-picked parts of the fossil record to serve their story—or the seven genes that best served their molecular clock estimates.

*sigh*. Again, it’s not that fossils are unreliable, it’s that they don’t catch everything. Imagine the ‘tree of life’ as determine from the molecular data as a diagram made of string. It’s stretchy, as string is, so you can’t just lay it out and expect it to be completely temporally accurate. But if you can take a pin and attach one point it to a known date, found from fossils, it becomes much more accurate and can be used to determine things much further back than the fossils can reach. They can have it both ways, as they don’t conflict.

The question of when and how the cambrain organisms evolved is legitimate – fossils get a bit grany when you get that far back, so you can never be sure about this or that. But it should come as no surprise that Mr Thomas is missing the point entirely.



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