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Mystery of How Early Animals Survived Ice Age Unraveled

How did life survive the most severe ice age? A McGill University-led research team has found the first direct evidence that glacial meltwater provided a crucial lifeline to eukaryotes during Snowball Earth, when the oceans were cut off from life-giving oxygen, answering a question puzzling scientists for years.

In a new study published in the Proceedings of the National Academy of Sciences of the United States of America, researchers studied iron-rich rocks left behind by glacial deposits in Australia, Namibia, and California to get a window into the environmental conditions during the ice age. Using geological maps and clues from locals, they hiked to rock outcrops, navigating challenging trails to track down the rock formations.

Maxwell Lechte samples iron-rich rocks within glacial deposits to try to understand the oxygen concentrations during Snowball Earth (Death Valley, California). (Image: Malcolm Wallace)
Maxwell Lechte samples iron-rich rocks within glacial deposits to try to understand the oxygen concentrations during Snowball Earth (Death Valley, California). (Image: Malcolm Wallace)

By examining the chemistry of the iron formations in these rocks, the researchers were able to estimate the amount of oxygen in the oceans around 700 million years ago and better understand the effects this would have had on all oxygen-dependent marine life, including the earliest animals like simple sponges.

Maxwell Lechte, a postdoctoral researcher in the Department of Earth and Planetary Sciences under the supervision of Galen Halverson at McGill University, said:

Researchers Ganqing Jiang, Malcolm Wallace and Alice Shuster head off into the desert in search of iron formations (Death Valley, California). (Image: Maxwell Lechte)
Researchers Ganqing Jiang, Malcolm Wallace, and Alice Shuster head off into the desert in search of iron formations (Death Valley, California). (Image: Maxwell Lechte)

Around 700 million years ago, the Earth experienced the most severe ice age of its history, threatening the survival of much of the planet’s life. Previous research has suggested that oxygen-dependent life may have been restricted to meltwater puddles on the surface of the ice, but this study provides new evidence of oxygenated marine environments. Lechte, who is also the study’s lead author, said:

Layers of glacial deposits, Death Valley (California). (Image: Maxwell Lechte)
Layers of glacial deposits, Death Valley (California). (Image: Maxwell Lechte)

Lechte points out that while the findings focus on the availability of oxygen, primitive eukaryotes would also have needed food to survive the harsh conditions of the ice age. Future research is needed to explore how these environments might have sustained a food web. A starting point might be modern ice environments that host complex ecosystems today. Professor Galen Halverson said:

Provided by: McGill University [Note: Materials may be edited for content and length.]

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Troy Oakes
Troy was born and raised in Australia and has always wanted to know why and how things work, which led him to his love for science. He is a professional photographer and enjoys taking pictures of Australia's beautiful landscapes. He is also a professional storm chaser where he currently lives in Hervey Bay, Australia.

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