Evolution of Animal Life Was Delayed

An international team of researchers lead by the University of California, Riverside have released a study on the chemistry of early Earth’s oceans, and how that chemistry may have inhibited the evolution of animal life by up to 2 billion years. The team tracked levels of molybdenum in black shales from this time period and found the amounts to be lower than expected. While life first evolved around 2.4 billion years ago, the first complex animal life didn’t arise until about 600 million years ago.

The researchers found significant, firsthand evidence for a molybdenum-depleted ocean relative to the high levels measured in modern, oxygen-rich seawater.

“These molybdenum depletions may have retarded the development of complex life such as animals for almost two billion years of Earth history,” Lyons said. “The amount of molybdenum in the ocean probably played a major role in the development of early life. As in the case of iron today, molybdenum can be thought of as a life-affirming micronutrient that regulates the biological cycling of nitrogen in the ocean.

“At the same time, molybdenum’s low abundance in the early ocean tracks the global extent of oxygen-poor seawater and implies that the amount of oxygen in the atmosphere was still low.

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