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ScienceNOW: “Did ‘Snowball Earths’ Trigger Animal Evolution?” Could global ice ages have “triggered” evolution—or is it just another wild idea that works on paper but lacks actual evidence?
A team led by Woods Hole Oceanographic Institution biogeochemist Noah Planavsky claims to have uncovered a possible link between severe ice ages nicknamed “snowball earth” and the evolution of oxygen-breathing life-forms in earth’s history. The research is reported in the journal Nature.
Levels remained constant over time with the exception of a “surge” during an estimated 635–750 million years ago.
So-called “snowball earth” glaciations, thought to have occurred multiple times in earth’s history, covered the planet almost completely in ice. (Most creationists, by contrast, think the evidence for the most recent of these ice ages points to a single multifaceted Ice Age that came about as a climatic consequence of the global Flood, while the evidence for the earlier so-called ice ages can be better explained as catastrophically deposited debris layers.)
Planavsky’s team measured the phosphorus content of certain minerals thought to have formed in ancient oceans, finding that levels remained constant over time with the exception of a “surge” during an estimated 635–750 million years ago. This fits in roughly with the appearance of the earliest animals in the fossil record. But is there a connection?
According to the researchers, glaciation would have broken up rock, releasing phosphorus that would have washed into the oceans as the glaciers melted (hence the surge). There, the phosphorus could have stimulated algae growth, leading to more oxygen production in the oceans. Eventually the level of atmospheric oxygen would have risen as well, easing (hypothetically) the evolution of oxygen-breathing animals.
For University of Southern Denmark biogeochemist Donald Canfield, however, the idea “is a fascinating possibility” but lacks “the continuous [geologic] record that would prove it.” Additionally, critics have pointed out that the phosphorus release from deglaciation would be insufficient to substantially influence ocean life, thereby short-circuiting the hypothesized increase in oxygen production. Our problem, however, goes back to the root of evolutionary ideas: in what way does the presence of oxygen imply that life could have evolved to breath it? The vague, unevidenced answer of genetic mutation just isn’t good enough.
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