Learning about the first animals on Earth from life at the poles

The amazing survival strategies of polar marine creatures might help to explain how the first animals on Earth could have evolved earlier than the oldest fossils suggest according to new research. These first, simple and now extinct, animals might have lived through some of the most extreme, cold and icy periods the world has ever seen. The study is published in the journal Global Change Biology, published this week (12 October 2022).

The fossil record places the earliest animal life on Earth at 572-602 million years ago, just as the world came out of a huge ice age, whilst molecular studies suggest an earlier origin, up to 850 million years ago. If correct, this means that animals must have survived during a time influenced by multiple global ice ages, when the whole or large parts of the planet were encased in ice (snowball and slushball Earths), far bigger than any seen since. If animal life did arise before, or during, these extreme glacial periods it would have faced conditions like modern marine habitats found in Antarctica and the Arctic today, and required similar survival strategies.

Over millions of years, the expansion and contraction of the ice sheets during cold and warm periods has driven the evolution of Antarctica's thousands of unique animals and plant species. The same could be true for the evolution of animal life on Earth. Whilst to humans the polar regions seem like the most hostile environments to life, they are the perfect place to study the past and the potential for life in the universe beyond our planet, such as on icy moons like Europa.

Marine biologist and lead author, Dr Huw Griffiths of British Antarctic Survey (BAS), says:

"This work highlights how some animals in the polar regions are incredibly adapted to life in and around the ice, and how much they can teach us about the evolution and survival of life in the past or even on other planets.

"Whether it is animals living upside down on the underside of ice instead of the seafloor, sponges living hundreds of kilometres under thick floating ice shelves, organisms that are adapted to live in seawater colder than ?2°C, or whole communities existing in the darkness on food sources that don't require sunlight, Antarctic and Arctic life thrives in conditions that would kill humans and most other animals. But these cold and icy conditions help to drive ocean circulation, carry oxygen into the ocean depths and make these places more suitable for life."

Floating ice covers more than 19 million km2 of the seas around Antarctica and 15 million km2 of the Arctic Ocean during winter. Under possibly the most extreme snowball Earth, lasting 50 to 60 million years during the Cryogenian period (720 to 635?million years ago), the whole world (510 million km²) is believed to have been entombed in ice around a kilometre thick, but there is some evidence that this ice was thin enough at the equator to allow marine algae to survive.

"The fact that there is this huge difference in the timing of the dawn of animal life between the known fossil record and molecular clocks means that there are huge uncertainties about how and where animals evolved" says co-author Dr Emily Mitchell, palaeontologist and ecologist at the University of Cambridge. "But if animals did evolve before or during these global ice ages, they would have to contend with extreme environmental pressures, but ones that may have helped to force life to become more complex to survive."

"Just like in Antarctica during the Last Glacial Maximum (33-14 thousand years ago), the huge amounts of advancing ice would have bulldozed the shallows, making them inhospitable to life, destroying fossil evidence and forcing creatures into the deep sea. This makes the chances of finding fossils from these times less likely and sheltered areas and the deep sea the safest places for life to evolve."

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Refreezing poles feasible and cheap, new study finds

The poles are warming several times faster than the global average, causing record smashing heatwaves that were reported earlier this year in both the Arctic and Antarctic. Melting ice and collapsing glaciers at high latitudes would accelerate sea level rise around the planet. Fortunately, refreezing the poles by reducing incoming sunlight would be both feasible and remarkably cheap, according to new research published today in IOP Publishing's Environmental Research Communications.

Scientists laid out a possible future program whereby high-flying jets would spray microscopic aerosol particles into the atmosphere at latitudes of 60 degrees north and south -- roughly Anchorage and the southern tip of Patagonia. If injected at a height of 43,000 feet (above airliner cruising altitudes), these aerosols would slowly drift poleward, slightly shading the surface beneath. "There is widespread and sensible trepidation about deploying aerosols to cool the planet," notes lead author Wake Smith, "but if the risk/benefit equation were to pay off anywhere, it would be at the poles."

Particle injections would be performed seasonally in the long days of the local spring and early summer. The same fleet of jets could service both hemispheres, ferrying to the opposite pole with the change of seasons.

Pre-existing military air-to-air refuelling tankers such as the aged KC-135 and the A330 MMRT don't have enough payload at the required altitudes, whereas newly designed high-altitude tankers would prove much more efficient. A fleet of roughly 125 such tankers could loft a payload sufficient to cool the regions poleward of 60°N/S by 2°C per year, which would return them close to their pre-industrial average temperatures. Costs are estimated at $11 billion annually -- less than one-third the cost of cooling the entire planet by the same 2°C magnitude and a tiny fraction of the cost of reaching net zero emissions.

"Game changing though this could be in a rapidly warming world, stratospheric aerosol injections merely treat a symptom of climate change but not the underlying disease. It's aspirin, not penicillin. It's not a substitute for decarbonization," says Smith.

Cooling at the poles would provide direct protection for only a small fraction of the planet, though the mid-latitudes should also experience some temperature reduction. Since less than 1% of the global human population lives in the target deployment zones, a polar deployment would entail much less direct risk to most of humanity than a global program. "Nonetheless, any intentional turning of the global thermostat would be of common interest to all of humanity and not merely the province of Arctic and Patagonian nations," adds Smith.

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