How Volcanic Iron Delayed Life on Earth

If it weren't for iron and fire, we could be a much older species that we are now. Researchers from the Universities of Tübingen and Alberta claim that the heavy metals spewed from subsea volcanoes in Earth's adolescence poisoned early life on earth, delaying a boom in oxygen and life for a half-a-billion years.

That's at least according to a study recently published in the journal Nature Geoscience, which details how the widespread heavy-metal poisoning of primordial oceans can explain for the mysterious lag between the birth of Earth's first cyanobacteria, and the famous Great Oxidation Event (GOE) - which lead to the rise of complex life as we know it.

It has long been suspected that there was simple life on Earth even before the GOE, which somehow pumped loads of life-giving oxygen into our atmosphere 2.5 billion years ago. However, researchers only revealed concrete of evidence of cyanobacteria - the first oxygen producing photosynthetic organisms - this past September, after analyses of chemical weathering preserved in the ancient soils, or paleosols, were published in the journal Geology.

This discovery is essentially helping to rewrite evolutionary textbooks, but it also raised many questions as well - the primary one being, "why then, did it take so long for these organisms to impact the atmosphere on a global scale?"

Iron (Fe), the latest study asserts, could be to blame. The Tübingen and Alberta researchers reportedly exposed modern-day cyanobacteria to iron at levels matching those in ancient sediments - likely released in the subsea volcanic eruptions that were common during Earth's earliest years.

The team found that while iron can serve as an important nutrient for cyanobacteria, this primordial metal was too concentrated for the simple organisms to handle, reducing the volume of oxygen they pumped out by as much as 70 percent.

"We used the most conservative, lowest estimates of iron concentration to demonstrate that even if Fe²⁺ concentrations were low, the effect of iron toxicity on oxygen production is significant," lead researcher Elizabeth Swanner explained to New Scientist.

She and her colleagues believe that this would have been more than enough to delay the GOE, adding an important piece to the puzzle that is life's beginnings.

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