The ancient cave art in Alabama is probably the largest cave art in North America.

The new details of our past are being exposed and hidden in the corners and gaps of the world, because we have improved the technology to find them. The most valuable thing is that by analyzing our living and fossil DNA, we have reconstructed the human evolution that originated in Africa about 300,000 years ago.

Filled with the ghosts of the populations of Africa, Europe and Asia in the past, they can only be revived through scientific ability and the study of biomolecules entering the insignificant world.

Now, the digital analysis of the rock surface reveals how other ghosts in ancient times-this time from North America nearly 2,000 years ago-were coaxed into the light.

Jan Simek, a professor at the University of Tennessee, and his colleagues published a huge glyph image in Ancient magazine, which was carved on the mud surface of the low ceiling of a cave in Alabama.

These patterns depicting human figures and animals are some of the largest cave images found in North America and may represent the soul of black society.

In the first picture below, the diamond-shaped rattlesnake is the sacred beast of the native people in the southeastern United States, and it is nearly 3 meters long. The next picture is a human figure with a length of more than 1.8 meters.

(The photo was taken by S. Alvarez; Painted by j. Simek/anciency)

Above: snake-shaped head, diamond-shaped body marks. Please note that the bottom of the carved glyph is connected with a natural crack (3.3 meters long) in the limestone of the ceiling.

As far as the age of discovery is concerned, the ancients revived it by crashing a lamp (the burning torch of American bamboo) into the cave wall. This left a residue, and researchers were able to determine the year 133-433 with radioactive carbon. This is also consistent with the age of pottery fragments left by ancient artists in caves.

(The photo was taken by S. Alvarez; Painted by j. Simek/anciency)

Above: Rock painting figures in cave art,1.5438+0m high.

The problem is to look at the painting. The ceiling of the cave is only 60 cm high, so it is impossible to look back at the big picture. They can only be revealed by a technique called photogrammetry, in which thousands of overlapping photos of objects or places are taken from different angles and digitally combined in 3D.

Photogrammetry is a cheap technology, which is increasingly used in archaeology to record cultural relics, buildings, landscapes, caves and so on. This enabled Professor Simek's team to "lower" the bottom of the cave to 4 meters, which was enough for the complete pattern to appear for the first time.

Almost every continent has rock paintings, and the earliest rock paintings have a history of at least 64,000 years. We probably only know a small part of the rock art created in the past.

Pigment will darken and disappear; Thin carvings can be corroded away; The cave walls may collapse or be covered by carbonate sediments or mud. Assuming that more art does exist, unless we invest in research and new technology, we may never see it.

1979, more than a century after its discovery in Europe (altamira, northern Spain), rock paintings in dark areas of caves outside the natural light at the entrance of the cave were discovered in North America. It is known that about 500 caves in Europe contain rock art from 2.6 million to 1 1 700 years ago.

An example that is crucial to our own research can only be exposed through digital processing of the images we take. The following is a hand model in the cave of Martavieso (Estremadura, western Spain). When we looked for suitable samples in the cave to determine its artistic age, it did not appear immediately.

The template is covered by the accumulation of calcium carbonate deposits. We photographed the area, and then used digital image enhancement software to show the hand model (bottom and right side) very clearly.

(provided by the author)

Before it reappeared on our computer screen, this 64,000-year-old handmade template was still undiscovered despite 70 years of in-depth research in caves.

Light sculpture-a very common Pleistocene technology-is notoriously hard to see. Some of them may be illuminated by light shining at an oblique angle, which we call oblique light.

But using a technique similar to photogrammetry called reflection transform imaging (RTI), the 3D model can be illuminated from any angle. These can reveal more complete and complex images.

It is not easy to show this in a few stills, but I hope the two photos below the bison carved in a cave in El Castillo, northern Spain, can give people a taste.

(provided by the author)

Above: Digital photo of buffalo head carved in El Castillo cave, Spain (left), RTI image of the same buffalo head (right).

The archaeological search for rock art in the future may benefit from the latest development of airport security.

Full-body scanners use far infrared rays, which can safely penetrate clothes to show hidden weapons or contraband. Similar techniques have been used to "see through" the plaster layer of prehistoric walls and see the paintings below.

Who knows what will happen when these scanners become small enough and cheap enough to be taken into caves?