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The first animal ever to inhabit the Earth still lives among us

Sarah Kramer

2016-02-29T22:46:00Z

Sea sponges are amazing. They live in the tropics and under polar ice. They come in a huge variety of colors, can live a few months or decades, and are used for everything from scrubbing plates to tampons.

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And now, scientists from the Massachusetts Institute of Technology (MIT) have confirmed that the simple sponge may have been the animal that started it all 640 million years ago.

So while they're definitely not our evolutionary "cousins" in the way that chimpanzees are, they're quite possibly our most venerable predecessor confirmed to date.

Here's how scientists made the remarkable discovery.

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Biologists have long suspected sea sponges were one of the first multicellular organisms on the planet.

sponge underwater shutterstock

Sea sponge fossils even predate the Cambrian explosion 540 million years ago, when diverse multicellular life burst on to the scene.

globe sea sponge noaa

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Trouble is, fossils that old are hard to interpret — sponges are very, well, squishy. So it has been difficult to conclude they were the first animals.

illustration antique underwater ocean shutterstock

But scientists discovered that some of the sponge fossils contain evidence of a unique molecule that's still around today.

white sea sponge underwater ocean noaa

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Some algae and sea sponges today still produce the molecule, called 24-isopropylcholestane. It's a fatty lipid that's similar to cholesterol.

algae green underwater noaa — Green grape algae blooms. NOAA

Source: MIT News

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Researchers think sponges developed this gene around the same time the molecule appears in the fossil records.

sponge fossil wikimedia — Raphidonema faringdonense, a fossil sponge from the Cretaceous of England. Wikimedia Commons/Wilson44691

Which means that out of the over 8 million species alive on Earth, sponges were almost certainly the first.

sea sponge underwater flickr

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Unfortunately, our elderly relatives are coming under threat from the fishing industry and climate change.

natural sponge sea basket shutterstock

Source: United Nations Environmental Programme

Deep-sea conservation efforts are underway, though, so hopefully the world's longest-lived animal will stick around for a while longer.

us antarctica program scuba research ocean .JPG — A diver approaches a sea sponge in McMurdo Sound. US Antarctica Program/Rob Robbins

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