Startling new finding: 600 million years ago, a biological mishap changed everything

If life is effectively an endless series of photocopies, as DNA is transcribed and passed on from one being to the next, then evolution is the high-stakes game of waiting for the copier to get it wrong.

Too wrong, and you’ll live burdened by a maladaptive mutation or genetic disorder. Worse, you might never live at all.

But if the flaw is wrong in exactly the right way, the incredible can happen: disease resistance, sharper eyesight, swifter feet, big brains, better beaks for Darwin’s finches.

In a paper published in the open-access journal eLife this week, researchers say they have pinpointed what may well be one of evolution’s greatest copy mess-ups yet: the mutation that allowed our ancient protozoa predecessors to evolve into complex, multi-cellular organisms. Thanks to this mutation — which was not solely responsible for the leap out of single-cellular life, but without which you, your dog and every creature large enough to be seen without a microscope might not be around — cells were able to communicate with one another and work together.

Incredibly, in the world of evolutionary biology, all it took was one tiny tweak, one gene, and complex life as we know it was born.

“It was a shock,” co-author Ken Prehoda, a biochemist at the University of Oregon, told The Washington Post. “If you asked anyone on our team if they thought one mutation was going to be responsible for this, they would have said it doesn’t seem possible.”

The discovery was made thanks to choanoflagellates — tiny balloon-shaped creatures that are our closest living unicellular cousins — and a cool bit of evolutionary time travel known as ancestral protein reconstruction, which allows scientists to resurrect the genomes of long-dead creatures based on their modern descendants’ DNA.

In this case, the reconstruction took Prehoda and his colleagues back about 600 million years, when ancient beings no bigger than a single cell swam through vast shallow seas covering what are now continents. There’s pretty much no fossil record from this period — what kind of fossil could be left by something smaller than a pinhead? — so insights into life at that time rely on researchers’ imaginations and intense scrutiny of modern DNA.

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