13,000 years old skeleton found in submerged cave near Tulum

Human skeletal remains found in an underwater cave in Mexico are about 13,000 years old, providing more evidence of early human settlement in the Americas.

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Scientists reported in the journal PLOS One that the bones are another piece of a complicated puzzle, as experts have had difficulty pinpointing exactly when humans first migrated to North America and spread out, settling the rest of the continent and South America as well.

This ancient human’s remains were found in a submerged cave system near the archaeological site Tulum, which is on the Yucatán Peninsula in southern Mexico, about two hours south of Cancún in the state Quintana Roo. The scientists dated the bones with the help of a stalagmite in the Chan Hol cave that was growing on top of the skeleton’s pelvis. A stalagmite is a rock that grows vertically on a cave floor, the counterpart to the stalactite that hangs down from the top of the cave. These rock features form because of the way water drips down from the cave ceiling. Rainwater makes its way down into the cave, picking up organic material along the way. While it drips down, the calcite it is carrying solidifies and builds up over time, forming the stalactite. The calcite also builds up on the ground directly below that steady drip, forming the stalagmite.

Using information about how these vertical rocks grow, scientists can calculate how old they are.

According to the study, analysis shows that the stalagmite is more than 11,000 years old. An analysis of the bones themselves suggests they are even older, perhaps 13,000 years old.

The scientists say the ancient human died before the cave floor was wet, and the stalagmite formed later, after soft tissue had rotted away and the bone of the pelvis was already exposed.

“The Chan Hol individual confirms a late Pleistocene settling of Mesoamerica and represents one of the oldest human osteological remains in America,” the authors wrote.

There has been some debate about when humans first arrived in North and South America and what routes they took to migrate throughout the continents after traversing the now-submerged land bridge called the Bering Strait that connected from Siberia to Alaska. While some experts estimate that crossing happened 13,000 years ago, with dispersal through the continents following, others have pegged that crossing to 22,000 years ago.

The dating of the Chan Hol remains are right at the early limit of other recent findings. Earlier this year, scientists reported that the remains of a teenager found at Tulum, whom they nicknamed Naia, were dated to 13,000 years ago and they had found, based on evidence in her pubic bone, that she had given birth shortly before she fell into a pit and died. Her remains were discovered 180 feet down at the bottom of that pit, which is now filled with water and is known as Hoyo Negro — Spanish for Black Hole.

Naia’s nearly complete skeleton also gave her discoverers clues about what her life was like. Her teeth and long bones, like her femur, showed that she had lived through periods of famine, indicating that life was difficult for the people who first settled the Americas.

Although carbon-dating analysis suggests these two specimens from Hoyo Negro and Chan Hol are about 13,000 years old, the authors of this new study in PLOS One caution readers that the past climate in the cave could have contaminated the fossils, making them appear older.

The scientists are calling the age of the stalagmite growing over the pelvis, which they put at about 11,300 years old, plus or minus a few hundred years, the “minimum age for the skeleton.” That would place the remains right at the beginning of the Holocene epoch, which is the current geological era. If it is older, closer to the 13,000-year-old estimate, it would be in the preceding Pleistocene epoch.

“The oldest claims for humans in the Americas is based on tools, artifacts, scraps, and very little is based on osteological remains,” according to a paleo blog post from journal publisher Public Library of Science. “When bones are found, they are often very fragmentary.”

The Chan Hol skeleton was well-preserved, even though the site was looted shortly after its discovery and most of the bones were stolen.

“This skeleton, along with other remains found in the Chan Hol cave system, could represent an early human settlement along the sea,” the post says.

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13,000 years old skeleton found in submerged cave near Tulum

Mummified Bird, Baby Found in Cave Shed Light on Earliest Desert Farmers

The naturally mummified remains of a scarlet macaw — a tropical bird that’s not native to the Chihuahuan Desert — are among the intriguing funerary goods found in the grave. 

Archaeologists called to investigate a cave on a rancher’s property have discovered an unusual burial that’s providing new insights into the ways of some of the earliest farmers of the Chihuahuan Desert.

In the cave, researchers have found the skeleton of an infant, the lower half of a man whose legs were tied together, and the remains of a scarlet macaw, all buried among a scattering of stone points, textiles, and other artifacts.

Some of the remains — both human and avian — had been naturally mummified by the arid climate.

The find was made in central Chihuahua, near the town of San Francisco de Borja some 300 kilometers from the Texas border.

It’s the first archaeological site ever found in the area, and it’s yielding new clues about the lives of some of the region’s earliest argriculturalists and a period known as the Late Archaic, some 2,000 years ago.

“This is one of the few archaeological contexts registered by archaeologists in this region,” said Dr. Emiliano Gallaga Murrieta.

“If we confirm the hypothesis [that this burial dates from] the Late Archaic, we could have a site with information about the transition to agricultural, sedentary communities in the region.”

Gallaga and his colleagues fromof Mexico’s National Institute of Anthropology and History were called to the site in March, after a rancher in San Francisco de Borja was using heavy equipment to level the floor of the cave and uncovered strange remains, including the mummified head of a macaw.

“Many archaeological discoveries are the result of planned research and are conducted during years of intellectual efforts,” Gallaga said. “Others are the result of an accident.”

Over the next two weeks, excavations unearthed human remains as well, beginning with the partial skeleton of a toddler.

The sex of the child is unknown, as is its exact age, although Gallaga estimates that it was between one and three years old at the time of death.

“This burial was close to the surface and very disturbed,” he said.

The team then unearthed the partial remains of at least one more person, consisting of a partial pelvis and two sets of large leg bones, which had been bound together with cordage.

Such bound partial remains have been found in other, more recent contexts in northern Mexico, Gallaga explained.

“It is not uncommon to find reburied partial skeletons,” he said.

The practice was common, for example, in the large pre-contact city of Paquime, or Casas Grandes, about 350 kilometers to the north, a trading hub that connected the cultures in the southern tropics to the Ancestral Puebloans and beyond.

Beginning around 1100, the people of Paquime were known to dig up and re-bury their dead, sometimes depositing their bones in bundles or large jars, possibly so that they could be interred with relatives.

Assuming that this newly found cave site predates Paquime, the San Francisco burial could be early evidence of this practice, Gallaga said.

“Probably the burial was [originally] buried somewhere else, and then only half of the body was reburied at the cave,” he said.

“But why? We do not know.

“The remains of the baby were close to the half adult burial, but we do not know if they are related.”

The two sets of remains were surrounded with an array of goods, including baskets, textiles, a bag or dress made out of deer hide, and a large sea shell.

But conspicuously absent from the graves were ceramics and other artifacts associated with the so-called Medio Period, when Puebloans built and settled in farm and trade centers like Paquime.

This absence suggests that these graves predate the establishment of Paquime, around the year 700, Gallaga said.

“[Based on] the lack of material from the Medio Period and the presence of some diagnostic material, we think the cave is Late Archaic, but only carbon-14 [dating] will prove or contradict this hypothesis,” he said.

This early date also lends special significance to the macaw, Gallaga pointed out, because the tropical birds, like seashells, are not local to the high desert of Chihuahua.

The discovery of the bird in this pre-Medio Period burial suggests that long-distance trade in exotic goods — and wildlife — pre-dated Paquime by centuries.

“This finding verifies once again that the [mountains of Chihuahua] have been a cultural corridor between the coast and the desert north with the south,” Gallaga said, in a separate press statement.

Mummified Bird, Baby Found in Cave Shed Light on Earliest Desert Farmers