What Rotting Fish Reveal About The Fossil Record

Fish full body shot

hide captionThis sequence of images shows changes to the bodies of Amphioxus, also known as the lancelet, during decay. It has only a primitive proto-spinal column called a notochord, but it is a close relative of vertebrates. The variation in colors is caused by interference between the equipment and the light illuminating the fish.

Mark Purnell, Rob Sansom and Sarah Gabbott

Anyone with a functioning nose probably wants to stay away from rotting fish, but a team of British researchers braved the stench — and turned something gross into scientific gold.

According to a study just published in the journal Nature, fish — and other living creatures — don't decompose in a random order. It's the newly evolved parts that go first.

That could have a major impact on the way we read the fossil record. Dr. Rob Sansom is a researcher at the University of Leicester and the leader of the study. He tells NPR's Guy Raz that decomposition plays an important part in the formation of fossils.

Sansom and his team were hoping to find out more about the oldest branches of our family tree. He says fossils from that era — about 500 million years ago — often don't give researchers much information to work with.

"At this part of the fossil record, we don't have any bones or teeth, so the fossil record can be very difficult to interpret," he says. Complex soft structures like tentacles and sensory organs decay too fast to become fossilized, and that means it's hard to tell how evolved an animal really was.

Fish heads

hide captionAmphioxus diverged from vertebrates more than 500 million years ago, and is often studied by researchers hoping to learn more about the early history of vertebrates.

Mark Purnell, Rob Sansom and Sarah Gabbott

"You can end up with an organism, or a fossil, that may look more primitive than it may have been in life," Sansom say.

Sansom says the new research means scientists will begin to get a better picture of our earliest ancestors. "We now have a framework of data with which to interpret these fossils, and place them more correctly in the tree of life," he says.

But that new knowledge came with a price. Sansom says he and his colleagues caught fish in the wild and put them in boxes to watch them decay as part of their research. That made his laboratory one of the least popular places on the University of Leicester campus.

"I've grown used to the smell for now," he says, "but colleagues and visitors are less keen."

University Of Leicester Video

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