I’ll post my new story below — it’s about a fossil discovery in the Yucatan. Big roll-out in Science, with a teleconference highlighted by a couple of questions from the legendary science journalist David Perlman (look him up — that’s the guy I want to be in my 90s!). Our graphics team has done a great job putting together not only a diagram of the cave and illustrations of what has been found there — saber-toothed cats, lots of bears, etc. — but also has created an image of Naia, the 15-year-old girl whose remains were discovered by scuba divers. Mitochondrial DNA tests suggest that she — and all Paleoamericans, and all more modern Native Americans — come from the same ancestral population, one isolated in Beringia during the Ice Ages. This is a long way from being a settled matter, as you’d expect with such a hot scientific topic. Here’s the top of my story:

By J.A.

The divers found her on a ledge, her skull at rest on an arm bone. Ribs and a broken pelvis lay nearby. She was only 15 years old when she wandered into the cave, perhaps in search of water in an era when the Yucatan was parched. In the darkness she must not have seen the enormous pit looming in front of her.

More than 12,000 years later, in 2007, after the seas had risen and the cave system had filled with water, her skull — upside down, teeth remarkably intact — caught the eye of a man in scuba gear.

The divers gave the girl a name: Naia. Her remains may help determine the origins of the earliest Americans and finally solve the mystery of why they looked so dramatically different from the Native Americans of recent millennia.

A paper published Thursday online in the journal Science argues that the discrepancy in appearance between the Paleoamericans and later Native Americans is most likely the result of recent, and relatively rapid, human evolution — and not the result of subsequent migrations of people into the Americas.

Tests on samples of mitochondrial DNA taken from Naia show that she has a genetic marker common today across the Americas, one that scientists say evolved in a prehistoric population that had been isolated for thousand of years in Beringia, the land mass between Alaska and Siberia that formed a bridge between the continents during the Ice Ages.

Thus, according to the new report, the Native Americans and the Paleoamericans are the same people; they just look different because of evolutionary changes.

“This is truly an extraordinary discovery,” said Yemane Asmerom, a University of New Mexico geochemist who is a co-author of the new report. He compared the cave, known as Hoyo Negro (“black hole”), to the Awash Valley of Ethi­o­pia — the site of the 1974 discovery of “Lucy,” an early human ancestor.

Most scientists have assumed that the first humans to come to the Americas crossed over from Eurasia across the Bering land bridge that existed before the oceans rose after the Ice Ages. But there is great debate about whether this represented a single migratory event or multiple pulses of people from different parts of Eurasia and via different routes, including a coastal migration. One maverick theory, based on archeological finds, contends that people came from Europe, following the edge of the ice around the North Atlantic.

Adding to the mystery is that the Paleoamericans, such as Naia, don’t look like later Native Americans. Naia had a small, projecting face, with narrow cheekbones, wide-set eyes and a prominent forehead. Her profile would resemble that of an African more than a Native American, said James Chatters, an independent researcher based in Washington state and the lead author of the new paper.

This distinct morphology is most famously found in the “Kennewick Man,” a 9,000-year-old skeleton discovered two decades ago along the Columbia River in Washington state. Facial reconstruction resulted in someone who looked a bit like the actor Patrick Stewart (“Star Trek,” “The X-Men”). Scientists theorized that he could have been related to populations in East Asia that spread along the coast and eventually colonized Polynesia; modern Native Americans may have descended from a separate migratory population, under that scenario.

Chatters said in an interview, “For 20 years I’ve been trying to understand why the early people looked different. The morphology of the later people is so different from the early ones that they don’t appear to be part of the same population.”

He went on: “Do they come from different parts of the world? This comes back with the answer, probably not.”

[Keep reading.]