Wednesday, July 7, 2010

Musings on coral reefs and creationism

I read an interesting article on coral symbioses in PNAS last week, which set me to thinking about creationism and coral reefs. Corals come in several varieties. Many corals are solitary creatures that grow in deep water. The more familiar reef-forming corals live in colonies and have photosynthetic symbionts called zooxanthellae. They make sometimes giant reefs, and given the growth rate of corals, these monstrous reefs have been something of a problem for creationist chronology, which would limit modern reefs to at most 4500 years old. For example, parts of Australia's Great Barrier Reef are thought to be as much as half a million years old. Creationists have written about reefs on numerous occasions (Roth, Roth again, Hodges, others).

I'm not well-versed in creationist responses to the coral reef problem, but I was intrigued by Barbeitos et al.'s article on loss of coloniality and symbiosis in coral phylogeny. The existence of symbiotic, colonial corals and nonsymbiotic, solitary corals could be explained in different ways. One could imagine a clade (or baramin) of reef corals and another clade (or baramin) of non-reef corals. Molecular phylogenies support the mixing of the two groups in various clades, which raises the question of how many times reef corals have arisen. Barbeitos et al.'s research supports the idea of a single origin of reef corals from which the non-reef corals have been derived.

These results got my creationist brain wondering how intrabaraminic variation in reef-building ability might relate to the growth of modern coral reefs and structures thought to be fossil reefs. I simply don't know how much baraminology has been brought to bear upon the reef problem, but I strongly suspect that it may play a significant role in understanding the origin of reefs. Unfortunately, there has been no (to my knowledge) attempt at coral baraminology, which would serve a significant role in developing a good understanding of reef growth. So we're just left with Barbeitos et al.'s tantalizing phylogenetic study.

The paper is open access, so you can read it for yourself:

Barbeitos et al. 2010. Repeated loss of coloniality and symbiosis in scleractinian corals. PNAS DOI 10.1073/pnas.0914380107

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