Friday, May 16, 2014

Dating a 13,000-year-old girl from Mexico

Diver Susan Bird places the Hoyo Negro skull on a turntable to be
photographed from multiple angles to create a 3D model.
Credit: Paul Nicklen/National Geographic.  Image source.
Numerous news sources reported today on the skeleton of a teenage girl, which researchers named Naia, found in an underwater cave in Mexico.  The cave, called Hoyo Negro (“Black Hole”), also contains the remains of numerous extinct mammals, including saber-tooth cats and gomphotheres, which are strange relatives of elephants.  The find was actually made in 2007, but extensive analysis and peer-review held off the announcement until the publication of the results in the most recent issue of Science magazine.

The significance of the find is twofold: First, according to the dates given by the researcher, this is the oldest intact human skeleton found in the Americas.  Second, morphological data and DNA analysis link the specimen with early immigrants from Asia and with the modern Native American populations, particularly those of South America.  Some scientists have proposed that there were two distinct ancient migrations of humans from Asia to America, citing the anatomical and genetic differences between paleoamericans and modern Native Americans.  This find, however, suggests that Native Americans may be descendants of the original migration rather than latecomers.

The interpretations regarding migration patterns are largely independent of the creation-evolution debate, aside from the timing.  Both creationists and evolutionists agree that the original Americans migrated from Asia to North America via a land bridge during an ice age.  Evolutionists view the "Ice Age" as a series of glacial events spanning back about 2.58 million years.  In fact, the present is considered to be merely a temporary warm period (‘interglacial’) within the current ice age.  Creationists, on the other hand, place a single Ice Age just after Noah's Flood 4400 years ago until about the time of Abraham, Isaac, and/or Jacob 400–600 years later.

The skeleton from Hoyo Negro was dated at 12,000 to 13,000 years.  Unsurprisingly, the age is mostly attributed to radiometric dating, specifically carbon dating and uranium-thorium dating.  An interesting article from Phys.org, however, reveals that the dating process was not that straightforward.  An attempt was made to directly date the bones using radiometric methods, but the methods “failed because the bones were mineralized.”  In that case, I find it odd that it was even attempted in the first place.  I wonder if the dates would have been used anyway had they matched expectation.  Instead, the established old-earth timeline of glaciation was used to determine that the sea levels rose enough to submerge the cave about 9,700 years ago, setting a minimum age for the bones contained therein.  Uranium-thorium dating was then performed on the teeth of the skeleton, as enamel is more resistant to degradation than bone, but that “did not work well,” according to the Phys.org article, which does not elaborate.  Instead, the scientists dated mineral deposits in the cave using the uranium-thorium method, arriving at an age of 12,000 years.  Because some of the deposits formed directly on the bones, the authors reasoned that the bones must therefore be older than 12,000 years.  The teeth of the skeleton were then carbon dated, giving an age of 12,900 years.  One of the authors admitted that the date could be thrown off by contamination from carbonate deposits in the cave, but it was accepted as a maximum age anyway because another researcher obtained similar results.

Unfortunately, I am unable to find any information on the rejected radiometric results, so I do not know whether they were ignored due to insufficient material or to unacceptable results.  I strongly suspect, however, that the uranium-thorium date of the teeth would have been accepted if it had fallen in line with the expected timeline, and that the radiocarbon date would have been thrown out for contamination if it had done the opposite.  This is yet another example of the impact of researcher bias on supposedly unbiased dating techniques.  For more information on radiometric dating, see my previous series on the topic.  As I have told others, radiometric dating is really only used to determine the sequence of events within an old-earth timeline, which it frequently assumes.  It is not independent of the bias and assumptions of researchers, so it cannot be used as proof of the age of the earth.

As for Naia, she probably was a descendant of Asian migrants and an ancestor (or sibling to an ancestor [aunt-cestor?], since she likely did not have children) of modern Native Americans.  Her family descended from Noah and made its way across Asia and into North America within a few hundred years.  I do not think this view is untenable at all, and it does not contradict Scripture or science.

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