Naia, an ancient human skeleton in Mexico: why it’s in the news and why it’s important

You might have seen some stories in the news lately about a skeleton of a young woman that was found in a cave in Mexico.  If you’re anything like me, you think that any find like this is interesting and important.  But not every such find makes the news.  Wondering why this particular discovery, published last week in Science, caused such a stir?

It’s because this young woman (whom researchers called “Naia”) carries in her bones, in her DNA, a story not just of herself but of where and when and how humans arrived in North America.  She also speaks to modern questions of how archaeological bones are interpreted.

Here are the basics: in 2007, divers in an underwater cave in the Yucatan Peninsula in Mexico found a deposit of bones.  Lying among the bones of sabertooth cats, mountain lions, and a gomphothere (an extinct relative of modern elephants) were the remains of a young woman, about 16 years old.  Naia probably fell in and died, over 12,000 years ago (during the last Ice Age, lots of the world’s water would have been tied up in glaciers and the sea level would have been lower than it is now), when this underwater cave was a trap, an open sinkhole in the ground.

The teen’s mitochondrial DNA, extracted from a tooth, confirms what scientists already believe based on other genetic studies of Native Americans: that Naia’s ancestors were of Siberian (or more specifically, Beringian) origin.  The DNA of modern Native Americans, too, reflects a Siberian ancestry.

But what if Naia’s DNA hadn’t been preserved?   What if we just had the bones themselves to go on?  Well, we’d have a different story.  Naia’s facial and cranial structures, based on measurements taken from her skull, don’t look much like those of modern Native Americans.  If we were going just on bone measurements, we’d have concluded that she wasn’t an ancestor of modern Native Americans, because her bones would tell a different story.

But DNA doesn’t lie, right? In this case, the DNA said one thing while the cranial measurements said another.  So what does this mean?  A couple of (really important) things.  First, it tells us that the cranial differences between more ancient Native American skulls and more modern Native American cranial structures are likely a result not of different ancestry but of changes that accumulated in the cranial structures of Native American populations AFTER they arrived in North America.  Or, to be more technical about it, it means that maybe we can’t be as sure, based on cranial measurements alone, about the ancestry of ancient Native American remains.  But this isn’t just a technical question.

Why? Because these remains have shown up WITHOUT expected Native American cranial features (like Kennewick Man, or the Ancient One), but WITH Native American DNA.  As others have pointed out, this suggests that maybe Kennewick Man IS a Native American.

In other words, it means that, as so often happens, we learned something new that shows us things are probably more complicated than we thought, and our assumptions will have to be re-examined and maybe changed. Every single time this happens, every time we realize we were (or even might have been) incorrect in our knowledge or assumptions, it’s an opportunity to learn.

*Please note that the information sources I used here are linked within the post.*

Advertisements

Tags: ,

About laurenwritesscience

I'm bringing scientific news and information to anyone interested, whether you're a scientist, or just love science! My focus is earth science and archaeology but I wander quite a bit.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: