July 14, 2014 in City

The Rock Doc: Skeletons give glimpse into lives of early humans

E. Kirsten Peters

I need to get a cap on my front tooth redone – it has a significant chip in it. Luckily I live at a time in which dentists are in every city and town, plying their trade in ways that can help us each day.

A young woman whom scientists are calling Naia was not so lucky. She lived about 12,000 to 13,000 years ago in what’s now the Yucatan Peninsula of Mexico. A recent article in New Scientist reports that Naia’s teeth have a number of large cavities in them. Her mouth likely hurt a lot when she was alive.

The name Naia comes from a derivative of the Greek for “water nymph.” Naia’s remains got their name because they were found in a flooded cavern. She was covered by water owing to ancient climate change. During the end of the Ice Age, when Naia lived, sea level was a great deal lower. Worldwide, glaciers melted as major climate change moved the globe in a warmer direction, so sea level rose. The waters covered Naia’s remains, helping preserve them for modern divers to discover.

Naia probably fell into a sinkhole in the rock of the area where she lived. She was not alone. Animals also fell into the hole, as we know from their remains. Some of the animals were giant sloths and sabertooth cats – creatures now extinct. But some, like the puma and cougar, are still with us. All of their remains were covered, along with Naia, by water as the sea rose.

While Naia’s remains don’t represent a complete skeleton, they constitute more than just a skull. There are complete arms and shoulders, one leg and a pelvis.

But back to Naia’s teeth. They show cavities and pits around the gum line, leading scientists to think Naia ate a lot of fruit or honey. Her small size and delicate bones suggest she may not have eaten much meat. And she may have gone hungry a good portion of the time.

Naia’s bones contain a special type of DNA known as mitochondrial DNA. Actually, all of us have mitochondrial DNA – it’s passed down from mother to child. I sometimes call this type of genetic material “mama-DNA.” Different populations of humans have different mama-DNA. Naia’s mama-DNA indicates she is related to ancient groups of people who lived in eastern Siberia. This fits with the view that North America was populated by people who crossed from Siberia to northern North America over a land bridge exposed because sea levels during the Ice Age stood so low.

Naia’s discovery in a flooded cave is an exciting development for archeologists and other researchers who study early human history in the Americas. We doubtless have a lot to learn about the people who first reached our shores. But with each discovery of bones and teeth, we come a bit closer to understanding the earliest history of those who originally populated our continent.

Dr. E. Kirsten Peters, a native of the rural Northwest, was trained as a geologist at Princeton and Harvard universities. This column is a service of the College of Agricultural, Human, and Natural Resource Sciences at Washington State University.

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