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Message:

> Starting 540 million years ago:
> 
> https://www.science.org/content/article/sea-creatures-began-glow-half-billion-years-ago?utm_source=sfmc&utm_medium=email&utm_campaign=ScienceAdviser&utm_content=distillation&et_rid=825383635&et_cid=5189169
> 
> "Some three-quarters of all undersea animals can generate their own light, but the origin of this ability has been shrouded in mystery. Now, research reported today in the Proceedings of the Royal Society B suggests the trait originated in octocorals at least 540 million years ago—nearly 300 million years earlier than scientists previously had thought.
> 
> ***
> 
> "Most bioluminescent animals use the same basic chemical reaction: an enzyme, luciferase, adds oxygen to a type of compound known as a luciferin, producing light as a byproduct. Previous research suggests this ability evolved at least 94 separate times, although some groups of animals that are predominantly bioluminescent contain a few “dull” members, which suggests the underlying chemical machinery was abruptly lost. “It’s a trait that blinks on and blinks off during evolution,” says Todd Oakley, an evolutionary biologist at the University of California, Santa Barbara who studies the origins of vision and bioluminescence and wasn’t involved with the study.
> 
> ***
> 
> "The researchers found that octocoral ancestors were lighting up the ocean some 540 million years ago—hundreds of millions of years before ostracods began spitting up their glowing goo.
> 
> "It’s a “breakthrough” for understanding the evolution of bioluminescence, says Edith Widder, a marine biologist and head of the Ocean Research & Conservation Association who specializes in bioluminescence.
> 
> "Although modern octocorals inhabit a range of depths, their ancestors predominantly occupied the ocean depths, DeLeo notes. In these dark conditions, the ability to glow may have helped them lure prey, communicate, or granted some other advantage. “In the deep sea, animals producing their own light is a way of life,” says James Morin, a marine biologist at Cornell University whose research laid the groundwork for our current understanding of bioluminescence in ostracods.
> 
> [b]"Still, researchers aren’t sure why the trait appeared in the first place.[/b] As Widder notes, many luciferins are excellent “scavengers” of harmful, unstable oxygen molecules known as free radicals, so the pathway may have initially evolved to shield cells from this oxidative stress. At first, light emission may have been mostly a byproduct. DeLeo says bioluminescence may also function as a type of “burglar alarm” for octocorals, allowing them to scare away would-be predators." (my bold)
> 
> Comment: light is always helpful, but these organisms don't have eyes. It is a mystery but developments in evolution always have reasons.