Independent Evolution of Complex Designs in Molluscs: Why the Explanations are in Need of Explaining

To the modern student Aristotle’s physics and cosmology are likely to seem bizarre. His final causes, geocentrism, and sublunar and superlunar realms seem to have no correspondence with reality. But Aristotelianism makes more sense when one understands the historical context of ancient Greek thought. In fact Aristotle’s physics and cosmology describe and explain what we observe in nature. This is attested to by the fact that it was well accepted and influential for a millenium and a half. Eventually, however, as scientific understanding progressed, the Aristotelian explanations became increasingly strained. Aristotelianism became more of a tautology, as whatever was observed was described according to the ancient system. Fire, for example, had the quality of dryness and heat. But is this not simply a tautology? As Descartes put it: “If you find it strange that … I do not use the qualities called ‘heat,’ ‘cold,’ ‘moistness,’ and ‘dryness,’ as do the philosophers, I shall say to you that these qualities appear to me to be themselves in need of explanation.” Aristotelianism failed to explain the physical action causing the effects. Today Darwin’s theory of evolution follows a similar denouement. To modern scientists it seems strange, but Darwin had good reasons for his theories of common descent and evolution. In the final acts, however, evolution is more of a tautology. Like Aristotelianism, evolution is a superfluous explanatory device rather than a value added. The difference is that evolution is running its course over a couple of centuries, rather than a couple of millenia.

Mollusca: A case study

Molluscs are mostly slugs and snails, but they also include larger, more advanced creatures, including the giant squid whose over-sized nerve cells have helped make it possible to study the physics and electrical properties of neurons.

The squids, along with others such as the octopus and cuttlefish make up the brainy side of the phylum and one would think (at least an evolutionist would think) that their more sophisticated central nervous systems would fall into the usual common descent pattern.

New research, however, suggests otherwise. It is a plot line that has played out over and over. Evolutionists arrange the species according to common descent, but when we look under the hood the species don’t cooperate. Contradictory differences in the supposedly closely-related cousins, and contradictory similarities in the supposedly distantly-related neighbors, betray evolutionary expectations.

In this case we now must believe that these advanced central nervous systems evolved independently, not once, but several times. Here is how one report summarized the new findings:

The findings, which rely on advanced statistical analyses, fundamentally rearrange branches on the mollusc family tree. In the traditional tree, snails and slugs (gastropods) are most closely related to octopuses, squid, cuttlefish and nautiluses (cephalopods), which appears to make sense in terms of their nervous systems: both groups have highly centralised nervous systems compared with other molluscs and invertebrates. Snails and slugs have clusters of ganglia – bundles of nerve cells – which, in many species, are fused into a single organ; cephalopods have highly developed central nervous systems that enable them to navigate a maze, use tools, mimic other species, learn from each other and solve complex problems.

But in Kocot's new family tree, snails and slugs sit next to clams, oysters, mussels and scallops (bivalves), which have much simpler nervous systems. The new genetic tree also places cephalopods on one of the earliest branches, meaning they evolved before snails, slugs, clams or oysters.

All this means that gastropods and cephalopods are not as closely related as once thought, so they must have evolved their centralised nervous systems independently, at different times.

That's a remarkable evolutionary feat. "Traditionally, most neuroscientists and biologists think complex structures usually evolve only once," says Kocot's colleague Leonid Moroz of the University of Florida in Gainseville.

"We found that the evolution of the complex brain does not happen in a linear progression. Parallel evolution can achieve similar levels of complexity in different groups. I calculated it happened at least four times."

Once again evolutionary expectations are at odds with reality, and once again the uncooperative empirical data are force fit to the theory. As with Aristotelianism, evolution does not add scientific knowledge. It does not tell us what to look for, and where to look for it. Quite the opposite, it is consistently turning up wrong. And yet the theory simply morphs to encompass the new, uncooperative results. No matter what is found, evolution is assumed to have created it. As one evolution remarked, concerning these new results, “This is more evidence that you can get complexity emerging multiple times.”

If you find it strange that I do not use the explanations of evolution, I shall say to you that these explanations appear to me to be themselves in need of explanation.

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