NH Notes: Underwater Cave Yields Fossilized Teenager From the Ice Age

Figure 1B and C from ??? et al. in Science (2014).
Figure 1B and C from Chatters et al. in Science (2014).  A shows a map of the cave system with the opening to the surface.  C shows the depth profile of the cave and location of the human bones.

During the last ice age some 12 to 13 thousands years ago a young girl found herself wandering in caves of the Yucatan Peninsula likely looking for water.  Hundreds of feet into a cave something happened and she fell in a deep pit breaking her pelvis. With no escape 100 feet down she died a lonely death.  She is surrounded by bones from extinct saber-tooth tigers,  giant sloths,  cave bears and many other animals. They were also probably looking for water in the caves when they met their demise.   Not long after her fall, the melting ice sheets that covered much of the northern hemisphere receded and the pit filled with water followed by the rest of the cave system.  She and the other animals have been laying there ever since.

Divers search the walls of Hoyo Negro, the underwater cave on Mexico's Yucatán Peninsula where the ancient skeleton was found. PHOTOGRAPH BY PAUL NICKLEN, NATIONAL GEOGRAPHIC
Divers search the walls of Hoyo Negro, an underwater cave on Mexico’s Yucatán Peninsula.
Photo by: PAUL NICKLEN, NATIONAL GEOGRAPHIC. Story at: http://news.nationalgeographic.com/news/2014/05/140515-skeleton-ice-age-mexico-cave-hoyo-negro-archaeology/

In 2007 underwater cave divers mapping the miles of labyrinth like caves underlying the Yucatan Peninsula came across the nearly complete skeleton of this teenager which they named “Naia”.  The bones had been mineralized (a form of fossilization) by the thousands of years of being bathed in the cave water.  A virtual lack of any sedimentation in the cave meant that even after all this time her bones were still lying on the surface waiting to be found. Yesterday, details of ongoing investigations of Naia’s life and death were reported in the journal Science.  There it was revealed that numerous dating methods have been employed which have confirmed the initial hypothesis that Naia died 12 to 13 thousand years ago.  More interestingly scientists have managed to extract DNA from one of her teeth.  That DNA has revealed that Naia had the same type of mitochondrial DNA that is shared by many Native Americans today.  This adds support to the dominant theory that all Native Americans can trace their origins back to groups of people crossing over from Siberian rather than the alternative theory that some native South Americans might have come via boat from the east Asian.

In a flooded cave in Mexico, divers transport a skull for 3-D scanning. Between 12,000 and 13,000 years old, the skull is part of the most complete skeleton of such antiquity yet discovered in the Americas. PHOTOGRAPH BY PAUL NICKLEN, NATIONAL GEOGRAPHIC
In a flooded cave in Mexico, divers transport a skull for 3-D scanning. Between 12,000 and 13,000 years old, the skull is part of the most complete skeleton of such antiquity yet discovered in the Americas.

The Ice Age Connection

A few weeks ago we learned about a hunting structure more than 100 feet below the Lake Huron (A man-made hunting structure found below Lake Huron) and before that I have written about Doggerland in Europe (Fishing for Fossils in the North Sea: The Lost World of Doggerland).  These are places that humans inhabited during the ice age when lower lake and ocean levels resulted from the massive amount of water bound up in glaciers on land.   These locations also attest to a time when there was a different set of animals as well.  Elephants, tigers, bears and other ice age animals roamed Europe and North America.

In the case of the Hoyo Negro cave it was likely formed at a time when the water levels were lower than today but not as low as during the peak of the last ice age. During ice ages ocean levels dropped more than 300 feet leaving this entire cave system dry with some possible lower levels with water.  During that time these caves could have been purposely visited or animals and people could have fallen into these caves from sinkholes and then made their way to other portions of the cave.  This particular site within the cave was very deep and animals likely had access to the higher part of the cave but then fell into this deep hole while looking for the water that was flowing through this portion of the cave. Since this is the only time in the history of this cave that these animal and human bones could have had access to these portion of the cave we can be quite certain that these bones are very old.

Ancient DNA Preservation

This story also caught my attention because it involved the use of ancient DNA, a topic which I’ve discussed several times on this blog (Young Earth Creationism and Ancient DNA and DNA from a Fossil Canine Skull).  Here is an example of DNA that has survived 12,000 years in a tooth preserved in sea water for thousands of years.  Even young earth creationists will likely agree that this skeleton is at least 4200 years old (this is when they think the Ice age began to end) and therefore DNA can survive must be able to survive at least that long even in wet and somewhat warm conditions found in the Yukatan.

National Geographic Story:  Most Complete Ice Age Skeleton Helps Solve Mystery of First Americans 

James C. Chatters et al. (2014).  Late Pleistocene Human Skeleton and mtDNA Link Paleoamericans and Modern Native Americans.   Science 344: 750-754

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