Scientists who study extinct life on Earth are stepping up the search for ancient DNA. They've managed to find it in the movies - remember the mosquito blood in "Jurassic Park"? - but not in real life; at least, not that far back in time. Now, a team has discovered something unique in a 46-million-year-old, fossilized mosquito. It's not DNA, but the chemical remains of its last, bloody meal.

NPR's Christopher Joyce has that story.

CHRISTOPHER JOYCE, BYLINE: If you think it's incredibly rare for a dinosaur to die and get fossilized for millions of years, imagine what it's like for a bug. Dale Greenwalt has.

DALE GREEWALT: Everything has to go exactly right, to become fossilized.

JOYCE: Everything did go right in a little corner of Montana millions years ago. There's a rock formation there, mostly shale, that's a veritable bug cemetery. Greenwalt collects fossils there.

Here's how bugs get into the shale. A mosquito, say, lands on a gooey mat of algae and microbes floating on a pond. It gets stuck and dies. And then...

GREEWALT: The algae and the microbes actually grow up and around, and encase and envelope the insect.

JOYCE: That protects the bug's corpse. The mat eventually sinks to the bottom and sediment slowly covers it, and it becomes rock. The bug's impression is preserved in stone.

What Greenwalt and a team from the Smithsonian Institution have found in one of those impressions is iron - a heck of a lot of it - as well as chemical compounds called porphyrins. They're in what was the mosquito's abdomen, nowhere else - preserved for 46 million years.

GREEWALT: And everyone was jumping up and down. And it was just because we knew this was exceedingly rare and important.

JOYCE: They were jumping up and down because iron and porphyrins are the brick and mortar of hemoglobin, the substance that carries oxygen in blood. What they had were the remains of the mosquito's last blood meal. Given the species of mosquito, Greenwalt guesses that its last feed came from a bird. He says the research is important because it demonstrates a technique that could turn up other chemical clues to ancient life.

The team describes the discovery in the "Proceedings of the National Academy of Sciences." Greenwalt says it was the Smithsonian's high-tech spectroscopy equipment that can detect tiny amounts of any element, that made this possible. Now, they're going to try their equipment out on more bugs.

GREEWALT: We have fossil insects that are bright yellow, bright red, bright orange; and there's probably preserved in those fossils a whole array of different types of pigments. I've got the next 10 years of my life all planned out ,working at the museum.

JOYCE: Considering that Greenwalt is a volunteer at the Museum of Natural History - he's been retired for years - this looks like a pretty good deal for the Smithsonian and for bug history.

Christopher Joyce, NPR News.


JOYCE: This is NPR.

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