Cambrian Explosion: oxygen not required (Introduction)

by dhw, Tuesday, January 02, 2024, 11:16 (326 days ago) @ David Turell

The Cambrian Explosion is indeed a mystery, as Darwin acknowledged. But I don’t think this article even begins to solve it.

QUOTE: “Contrary to a classical hypothesis, our interpretations place the Shuram excursion, and any coeval animal evolutionary events, in a predominantly anoxic global ocean.” Co-author Christian Bjerrum commented “Specifically, it means that we need to rethink a lot of the things that we believed to be true from our childhood learning. And textbooks need to be revised and rewritten. So, if not extra oxygen, what triggered the era’s explosion of life? Perhaps the exact opposite”.

“Perhaps.” This is pure sensationalism.

QUOTE: Some even went further and suggested to “forget everything you thought you knew about how life evolved on Earth” (Ralls 2023) because it “turns out we might be very wrong about how life arose on Earth” (Harrison 2023).

The Cambrian has nothing to do with the origin of life. More sensationalism.

QUOTE: His hypothesis (Towe 1970, 1981, also see: Saul 2009) is basically that two entirely new amino acids (i.e., hydroxyproline and hydroxylysine), which are required for the formation of structural glycoproteins such as collagen in metazoans, could only form under oxygen rich conditions and that explains the late origin of complex multicellular life after the “boring billion” of only bacterial and protist life. (dhw’s bold)

A totally different theory which emphasizes the richness of oxygen as an essential feature of the “explosion”, in keeping with current theory. I’ve read the whole article, and one reason why the authors attack this theory is:

QUOTE: 1.The availability of the two new amino acids may be a necessary condition for complex multicellular life but certainly not a sufficient condition to explain the sudden origin of numerous new body plans, which required new genetic code (Paps & Holland 2018) for new proteins, new tissues, and new complex organs as well as new ontogenetic pathways.

Precisely the same objection can be raised against their own theory. How does a lack of oxygen produce new body plans?

QUOTE: “The Cambrian explosion is real and its consequences set in motion a sea-change in evolutionary history” (Conway Morris, 2000; Nichols et al., 2006).

Not even Darwin denied its reality or its consequences!

QUOTE: "the abrupt appearance of animal body plan disparity stubbornly remains an unsolved problem for Darwinism.”

Agreed. And this article does not provide a solution to the problem. Whether the explosion was triggered by an increase or a decrease in oxygen is still not enough to explain HOW all the new body plans arose.