Back on May 19th, I wrote:
Oxygen is a biological output that, in turn, creates a new context to elicit further changes. Rising levels of oxygen are correlated to the two most radical transformations in evolution – the origin of eukarya and the origin of metazoa. There is no reason to think something as complex as the eukaryotic cell, or the metazoan body plan, would have emerged without oxygen.
A month later, a study came out that supports this line of thinking:
Toxic seas may have been responsible for delaying the evolution of life on Earth by 1 billion years, experts at Newcastle University have revealed.
The study, published online today in Nature Geoscience, reveals for the first time a chemical ‘layering’ of the ocean which may have delayed the evolution of our earliest animal ancestors. Using novel geochemical techniques developed by Newcastle University’s Dr Simon Poulton, the team found that beneath oxygenated surface waters, mid-depth oceanic waters were rich in sulphide about 1.8 billion years ago, conditions that may have persisted until oxygenation of the deep ocean more than1 billion years later.
These widespread sulphidic conditions close to the continents, coupled with deeper waters that remained oxygen-free and iron-rich, would have placed major restrictions on both the timing and pace of biological evolution.
In other words, the blind watchmaker was not able to cobble some metazoan-like life forms without sufficient oxygen, even though there was almost a billion years of trial and error. Apparently, there are not lots of ways to string together something like a metazoan. As it stands, it is quite reasonable to propose that the blind watchmaker had needs – it needed a eukaryotic cell plan and it needed oxygen (a biological output) to generate metazoa.
Chew on that one.