Unprecedented proof people occupied ‘lava tubes’ might fill in gaps within the archeological file, scientists say

Join CNN’s Marvel Principle science e-newsletter. Explore the universe with news on fascinating discoveries, scientific advancements and more.

Individuals who lived within the Arabian Peninsula hundreds of years in the past went underground once they wished to beat the warmth. Probably stopping there as they traveled between oases and pastures, they ducked into huge subterranean tunnels the place molten lava had as soon as flowed hundreds of thousands of years earlier, in line with a current research.

Starting within the Stone Age, Neolithic herders descended into and occupied these huge tunnels, often known as lava tubes, archaeologists have found. Cooler air underground would have supplied a welcome respite from the solar and wind, and for hundreds of years, people sheltered with their livestock within the tunnels. The herders left behind objects and even carved footage on the rocky partitions, researchers reported April 17 within the journal PLOS One.

Within the Harrat Khaybar lava discipline, about 78 miles (125 kilometers) to the north of Medina in Saudi Arabia is a tunnel system referred to as Umm Jirsan, the longest within the area. Scientists haven’t but confirmed the age of the lava that fashioned this method, however a 2007 study advised it was round 3 million years outdated. Umm Jirsan spans almost 1 mile (1.5 kilometers), with passages which might be as much as 39 toes (12 meters) tall and as a lot as 148 toes (45 meters) huge.

Archaeologists at Umm Jirsan not too long ago discovered animal bones relationship from 400 years to greater than 4,000 years in the past, and human stays starting from 150 years to about 6,000 years in the past. The analysis group additionally discovered material fragments, items of carved wooden and dozens of stone instruments — the primary proof that people have been utilizing the tunnels, beginning at the least 7,000 years in the past.

“From earlier experiences we knew that fossils have been preserved on the web site,” mentioned lead research writer Dr. Mathew Stewart, a analysis fellow on the Australian Analysis Centre for Human Evolution at Griffith College in Australia.

“Nevertheless, we weren’t anticipating to search out proof for human occupation within the type of rock artwork, lithic artefacts, stone buildings, and pottery,” Stewart informed CNN in an e-mail. “Folks made use of and occupied these lava tubes over millennia. Whereas most analysis in Arabia is concentrated on floor websites, underground settings equivalent to at Umm Jirsan provide super potential to fill in a few of the gaps within the information.”

This discovery highlights the importance of Umm Jirsan and different tunnels for understanding human dispersal within the area, mentioned Guillaume Charloux, an archaeologist with the French Nationwide Centre for Scientific Analysis. Typically, information about historical local weather and people in northwestern Arabia is restricted, “significantly throughout the transitional section between the Neolithic and the start of the 2nd millennium,” mentioned Charloux, who research historical websites in Saudi Arabia however was not concerned within the new analysis.                      .

Round this time, native individuals have been settling round not too long ago fashioned oases; the looks of those desert refuges would form human migration patterns within the area for millennia, he mentioned by way of e-mail. “The principle contribution of this revolutionary and main analysis mission appears to me to be that it brings to gentle the long-lasting use — in all probability ephemeral occupation — of such a cave, which had remained unstudied, and their monumental potential, significantly for understanding paleoenvironmental contexts.”

‘Inexperienced Arabia’

For almost 15 years, Stewart and his colleagues have been piecing collectively proof of historical human life in Arabia, largely from websites round lake deposits, Stewart mentioned. Starting round 400,000 years in the past, recurring durations of humidity saturated Arabian deserts with rainfall. Throughout these “Inexperienced Arabia” phases, lakes and ponds abounded and the panorama bloomed with lush vegetation, resulting in waves of migrating people who dispersed into southwestern Asia, Stewart and different researchers beforehand reported within the journal Nature.

However the final Inexperienced Arabia section was round 55,000 years in the past, and harsh desert environments aren’t type to archaeological proof. Whereas stone instruments protect nicely in dry deserts, bones and different natural supplies are simply degraded and destroyed by erosion and excessive warmth and chilly, leaving little for researchers to interpret, Stewart famous.

“To that finish, in 2019 we determined to research underground settings the place organics and sediments is perhaps higher preserved,” he mentioned.

So the scientists turned their consideration to Umm Jirsan. The positioning had beforehand been mapped by the Saudi Geological Survey, and a report from 2009 described it as a refuge for wild animals equivalent to foxes, wolves, birds and snakes. Caches of bones within the tunnels included human cranium fragments estimated on the time to be about 4,000 years outdated. However till 2019, the tunnel system hadn’t but been intently investigated by archaeologists, Stewart mentioned.

“We have been capable of date the animal bones and sediments, which knowledgeable us that individuals started occupying the cave by 7,000 years in the past and maybe as early as 10,000 years in the past,” Stewart mentioned.

In contrast with different websites the place people as soon as lived, the quantity of archaeological materials at Umm Jirsan was “fairly scant,” suggesting that individuals have been visiting the tunnels as short-term refuges relatively than dwelling there completely, the research authors reported.

Animal carvings

In one other tunnel close to Umm Jirsan, the researchers discovered 16 panels of engraved rock artwork. The carvings seemed to be herding scenes, with tool-wearing, stick-figure people standing alongside domesticated animals equivalent to canines, cattle, goats and sheep. Different carvings confirmed animals with dramatically arching horns resembling these of an ibex; nevertheless, these horned animals might symbolize a special breed of domesticated goat, in line with the research. The carvings’ topics and their varnish coating trace that they date to a regional interval often known as the Chalcolithic (round 4500 to 3500 BC), which preceded the rise of the Bronze Age.

“Collectively, the archaeological findings on the web site and within the surrounding panorama paint an image of recurrent use of the Umm Jirsan Lava Tube over millennia,” Stewart mentioned. The positioning — which lies alongside a identified migratory route for Bronze Age herders — “could have served as a stopping off level, a spot of refuge protected against the weather.”

This unprecedented proof of human occupation in historical Arabian lava tubes sheds gentle on how individuals tailored to dwell in arid landscapes, and additional investigation of Umm Jirsan and different lava tubes guarantees so as to add much more particulars, Stewart added.

“These websites have super potential to fill in a few of the gaps within the pure and cultural archives that persist within the Arabian archaeological file.”

Mindy Weisberger is a science author and media producer whose work has appeared in Dwell Science, Scientific American and How It Works journal.

For extra CNN information and newsletters create an account at CNN.com