The Archeotourist - Mesoamerica

If you are the type of tourist who plans a trip based on the ruins you can visit, and the first thing you do in a new city is visit a museum, then you are an archeotourist. My wife and I share a passion for archeology and have been fortunate enough to visit many sites and museums throughout the region. This blog is about sites you can visit, museum collections, books, exhibitions, articles, artifacts, anything that has do do with Mesoamerican archeology.

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Note:

There were two new archeology documentaries in February; one by NOVA about the remains found in the Hoyo Negro (The First Face of America), and one by National Geographic about the lidar mapping project in the Peten (Lost Treasures of the Maya Snake Kings). I got really worked up about the NOVA offering and wrote the review below. My write up on the archeology of Cozumel should go up in about 3 weeks,

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PBS NOVA, aired February 7th, 2018

Description: One unlucky day 13,000 years ago, a slight, malnourished teenager missed her footing and tumbled to the bottom of a 100-foot pit deep inside a cave in Mexico’s Yucatán. Rising seas flooded the cave and cut it off from the outside world—until a team of divers chanced upon her nearly complete skeleton in 2007. Intricate detective work reveals that the young woman’s bones are among the earliest known human remains in the Americas. What drove her to venture nearly a mile underground inside a vast cave? Where did her people come from, and why does she look so distinct from today’s Native Americans? From a stunning Mexico cave to the wilderness of the Yukon, from the genetics lab to the forefront of forensics, NOVA pursues tantalizing new clues that are rewriting the story of the forgotten first people who ventured into our continent.

My wife and I watched this show the day it aired and had fairly strong feelings about it. We have been following this story for a decade and were really excited at the prospect of finally seeing Naia formally presented to the world. For a number of reasons we didn’t like this documentary and what follows is my detailed dissection of it. If you are interested in Naia I encourage you to watch the documentary and decide for yourself what you think.

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Map and Diagram, Hoyo Negro Site, Quintana Roo Mexico

In 2007 three cave divers\explorers (Alex Alvarez, Alberto “Beto” Nava, and Susan Bird) heard rumors that divers at the Ich Balam cenote were finding prehistoric animal bones deep in the cave system. When they explored the cave system they found a huge pit cavern that they named “Hoyo Negro” or “Black Hole”. At the bottom of this pit they found a huge cache of incredibly well-preserved animal bones and miraculously they also found a human skeleton. This skeleton of a young girl, was named Naia and it is probably the oldest human remains found in the America’s.

This documentary covers in detail how Naia was found, how her bones were retrieved, how they were analyzed, and what they tell us about her. The documentary also tries to put Naia into the larger context of research on the peopling of the America’s. It discusses the findings at the Upward Sun site in Alaska and how genetic material from sites across North America is being used by the new science of Paleogenomics to try and answer the question of how the ancient America’s were colonized.

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Screen Capture, Yucatan Peninsula, First Face of America, NOVA Documentary

One of the weak points of the documentary is that it doesn’t take enough time explaining the geology and climate of the Yucatan. These provide the context for understanding Naia’s death and the preservation of her remains.

The Yucatan Peninsula, shown here, is the eastern most part of Mexico.  Situated in the tropics it has two seasons; a cool dry season from December to May, during which there is no rainfall, and a hot wet season from June to November of frequent, if not daily, rainfall. Geologically the peninsula is basically a giant slab of limestone. It is the remains of a series of gigantic reef systems that have formed and reformed here as ocean levels have risen and fallen over the millennia. Understanding this geology is necessary for understanding where Naia’s remains were found and how they were preserved for over 13,000 years.

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Screen Capture, Yucatan Peninsula Underground River System, First Face of America, NOVA Documentary

Karstic (limestone) geologies have some distinctive characteristics. Firstly, they are porous. Rainwater falling on them sinks into the ground rapidly, like water being poured on a sponge. Secondly, they are soft and dissolve easily in weakly acidic solutions. Rainwater, reacting with CO2 in the air and the calcium in the limestone, forms a weak solution of carbolic acid as it drains through the limestone bedrock. So, as it drains, it dissolves the rock and creates vast underground cave systems in the limestone. Shown here is a map of some of these huge cave systems that form a vast underground river and lake network beneath the surface of the peninsula.

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Screen Capture, Typical Yucatan Landscape, First Face of America, NOVA Documentary

On the surface, during the rainy season, the countryside is covered in lush green jungle and it is easy to imagine an idyllic life as a hunter gatherer here. However, this lush countryside is a deceptive deathtrap. Because of the geology, rainfall sinks into the ground almost immediately. There are no rivers, no streams, and no lakes. The only surface water is found in occasional shallow ponds (called bajo’s) that form in low spots where clay soils prevent the water from draining away.

During the rainy season, when it rains almost daily, this is a manageable issue. During the dry season, when there is no rain for six months and the bajo’s dry out, this lack of water becomes a matter of life or death. So how do animals and people survive here during the dry season? How do they access the water that has gone underground?

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Diagram, Cenote Life-cycle

The answer is the cenote. A cenote, or sinkhole, forms when the rock below the surface erodes away and forms a cavern. When the roof collapses, you have a big hole in the ground which is called a cenote. Cenotes are everywhere in the Yucatan but many of them do not have water in them, or the water is inaccessible from the surface. Finding cenotes with accessible water is crucial to surviving the long dry months.

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Personal Photo, Cenote Sagrado, Chichen Itza Site, Quintana Roo, Mexico

The cenote shown here is the main cenote at Chichen Itza, a large Maya city. As you can see, it is large (about 100’ across), the sides are very sheer, and it is about 50’ down to the water.

The Maya built\carved stairs down to the water, but keep in mind that in a society without pumps every gallon of water taken out of that cenote had to be hand carried back up those steps. Getting water during the dry season was a labor-intensive process, and this is an easy cenote to access. It can be much, much more difficult to get water from a cenote.

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Frederick Catherwood, The Well at Bolonchen, 1844

This painting by Frederick Catherwood was done in 1844 as an illustration for the book “Incidents of Travel in Yucatan Vols. 1 and 2” by John Lloyd Stephens. Stephens and Catherwood went to the cenote at Bolonchen (Village of Nine Wells) to observe how water was obtained. The arduousness of going into the caves through narrow, dark, humid, hot, passages with an 80’ descent on a wooden ladder at the end of the trek is described in their book but this illustration is worth a thousand words. They marveled that the men of the village would do this almost daily, but it was it was the only source of water for miles around. Descents like this, into the underworld to bring back water, were an inescapable feature of life in the Yucatan in the premodern world.

BTW: If you are interested in the archeology and history of the Yucatan, Stephens book is a great read and still relevant, even today. I highly recommend it.

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Diagram, Ox Bel Ha Cave System, Cenote-Ocean Interaction

The last important piece of the geology to understand is how sea level affects the water level in the cenote cave systems. The Wikipedia entry on the geology of the Yucatan explains it as follows:

The Yucatán Peninsula contains a vast coastal aquifer system, which is typically density-stratified. The infiltrating meteoric water (i.e., rainwater) floats on top of higher-density saline water intruding from the coastal margins. The whole aquifer is therefore an anchialine system (one that is land-locked but connected to an ocean). Where a cenote, or the flooded cave to which it is an opening, provides deep enough access into the aquifer, the interface between the fresh and saline water may be reached. The density interface between the fresh and saline waters is a halocline, which means a sharp change in salt concentration over a small change in depth.

The depth of the halocline is a function of several factors: climate and specifically how much meteoric water recharges the aquifer, hydraulic conductivity of the host rock, distribution and connectivity of existing cave systems and how effective these are at draining water to the coast, and the distance from the coast. In general, the halocline is deeper further from the coast, and in the Yucatán Peninsula this depth is 10 to 20 m (33 to 66 ft) below the water table at the coast, and 50 to 100 m (160 to 330 ft) below the water table in the middle of the peninsula, with saline water underlying the whole of the peninsula

In simpler terms, this means that there is a layer of fresh water (light blue in diagram above) that in essence “floats” on top of a layer of salt water (dark blue). When sea level goes down, the fresh water floating on top of it also goes down, and water drains out of the underground cave systems. When the sea level goes up, the salt water “lifts” or “pushes” the fresh water higher, and the cave systems flood.

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Screen Capture, Divers Exploring Yucatan Peninsula Underground Cave System, First Face of America, NOVA Documentary

Keeping the climate and geology of the Yucatan in mind it’s clear why the cave diving team was keen to check out reports of animal bones being found deep in the cenote cave system. While they are flooded now, during the last ice age, when sea levels were much lower, the caves would have been dry. Ice age animal bones have been found in other cenote cave systems in the Yucatan and finding new ones would be a major discovery. The first part of the documentary focuses on the diver’s initial descent into the cave and their discovery of the pit cavern they named Hoyo Negro.

This vast watery underworld is a unique ecosystem found nowhere else in the world. Exploring and mapping it has been a decades long project of dedicated amateur cave divers\explorers. This is a very dangerous type of diving with no room for mistakes. If you lose your light, you will probably die. If you get lost, you will probably die. If you knock some rocks lose and they fall on you, you will probably die.

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Diagram, Hoyo Negro Cavern

When the dive team found a sheer cliff with no bottom visible they cautiously descended until they reached the bottom of the pit. The Hoyo Negro is just over 100 feet deep and what they found at the bottom amazed them.

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Screen Capture, Ice Age Animal Bones, Hoyo Negro, First Face of America, NOVA Documentary

As shown in the documentary they found animal bones like this, everywhere on the floor of the cavern.

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Screen Capture, Ice Age Animals, Hoyo Negro, First Face of America, NOVA Documentary

The Hoyo Negro turned out to be a treasure trove of ice age animal bones. Like the famous La Brea tar pits of Los Angeles, it was a natural trap. Animals coming into the cave looking for water would fall off the cliff, down 100 feet, and die. In the anaerobic (oxygen poor) water at the bottom of the pit their bones were perfectly preserved. Shown here are all the animals whose bones were found. A snapshot of the Yucatan ecosystem circa 11,000 BCE.

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Screen Capture, Finding Naia, Hoyo Negro, First Face of America, NOVA Documentary

The divers were understandably thrilled by their discovery but then the unbelievable happened; they saw a human skull on the cavern floor.

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Screen Capture, Finding Naia, Hoyo Negro, First Face of America, NOVA Documentary

What they had discovered was the almost complete skeleton of a young woman from the end of the ice age, 13,000 years ago. They named her Naia and her remains are probably the oldest human remains ever discovered in the Americas. It was the find of a lifetime, priceless beyond words.

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Screen Capture, El Museo Nacional de Antropología – INAH, Mexico City, First Face of America, NOVA Documentary

The cave divers knew they had made an incredible discovery that had to be handled by Mexico’s National Institute of Anthropology and History (INAH). After carefully recording their find they sent full documentation of the find to INAH’s headquarters in Mexico City. The documentary recounts in detail the retrieval of Naia’s remains, their transport to Mexico City, and their analysis.