New Dating of Cave Art Reveals History of Puerto Rican People
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Pittsburgh, Pa., USA: In the karstic caves of Puerto Rico, cave art paints
the rock walls. Previous research has assigned ages to this art based on
the ages of nearby archaeological artifacts within the caves, but these
ages are relative and may not reflect the true timing of the art creation.
Now, a new study to be presented Wednesday at the Geological Society of
America’s GSA Connects 2023 meeting shows that researchers have refined the
age of this rupestrian art by dating the pigment in the drawings. Angel
Acosta-Colon, a geophysicist at University of Puerto Rico (UPR) at Arecibo,
present the findings.
In Puerto Rican caves, there are three types of art: petroglyphs (carved
into the rock), pyroglyphs (drawn from the burnt remnants of objects), and
pictographs, or cave drawings. Acosta-Colon says these pictograph drawings
are in organic black material, perfect for radiocarbon dating.
Acosta-Colon and his colleague Reniel Rodríguez, an archaeologist at UPR
Utuado, visited 11 different caves on La Isla Grande, the big island of the
Puerto Rican archipelago. From these caves, they sampled 61 pigments in
The researchers were thoughtful about which art to sample, sampling art
that is commonly seen and not unique. “[The pictographs] are not an
infinite resource—they are limited,” explains Acosta-Colon. “So if we touch
one, we touch it forever and for the future generations, we are not allowing
the pleasure of seeing what we see.”
They were also conservative about how much of the material they collected,
as sampling destroys a small area of the art. Acosta-Colon says that they
take 1 to 2 mg samples from the black markings on cave walls for their
They ran the microsamples through the Center for Applied Isotope Studies
(AIS) at the University of Georgia to get carbon-14 ages for the
artwork. The earliest pictographs of abstract, geometrical shapes were
dated to ca. 700–400 BCE, coinciding with the
“That is very important to us because when the European Invasion came to
Puerto Rico, they put in a document that our precolonial population was
only there for 400 to 500 years,” says Acosta-Colon. “So this proves that
we were here [thousands] of years before the European Invasion, and that is
documented in science, not context archeology.”
They found that more anthropological-type drawings—with simple shapes of
human bodies—were drawn between 200 and 400 CE. “We have gaps of time and
that's interesting because we don't know what happened,” says Acosta-Colon,
adding that they could fill those gaps with more sampling around the
The research team also found more detailed human and animal drawings that
were created between 700 and 800 CE. These types of drawings continued
throughout the next century, extending through European colonization
(around 1500 CE), and include images of horses, ships, and other animals.
Within the array of animals, they discovered a particularly unusual find.
“We have an image that looks like a lion—but in Puerto Rico, we don’t have
lions,” says Acosta-Colon. When he and Rodriguez considered who could have
seen a lion, they thought about the slaves that were brought to the island
by the Spanish.
The idea, he notes, is controversial. “But the age of the art is around
1500,” he says. “We have data to corroborate what, I think, is one of the
first slave art in caves in Puerto Rico.”
Understanding when these pictographs were created helps explain the history
of the Puerto Rican people, says Acosta-Colon. “Normally we get the
European history version of Puerto Rico, but this is direct evidence that
the story in Puerto Rico didn’t start with the European Invasion, it
started much, much earlier in history,” he notes.
He believes that studying more cave art sites may push back the human
history record to 5000 BCE. This art, along with archeological finds, can
reconstruct the “history of our people, from Archaic people, to the Taino
people to the pre-Columbian time.”
Radiocarbon dating of cave pictographic rock art in Puerto Rico
Contact: Angel Acosta-Colon, firstname.lastname@example.org
208: D11. Recent Advances in Geoarchaeology: Studies from Asia, Europe
and the Americas
Wed., 18 Oct. 2023, 10:20–10:35 a.m.
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