You could call them the ultimate excavators: Bulldozing dirt that’s 10 times their body weight, they can survive underground in thin oxygen, they work for literally peanuts, and, being remarkably resistant to cancer, they don’t even take sick days.
A team of Israeli archaeologists proposes that Middle East blind mole-rats, with their massive numbers and burrowing skills, be systematically harnessed for cheap labor. And in fact, analysis of their molehills just may constitute a revolution in archaeological best practices.
Instead of taking hours — or even days and weeks — to complete complicated and time-consuming surveys in search of hidden ancient sites, the Bar-Ilan University researchers propose systematically studying dirt from molehills, or other rodent dirt piles, to more efficiently and cheaply ascertain loci of human activity from the past.
The researchers’ eureka moment was a long time coming. During the course of a decade-long study of Tel ‘Eton, a fascinating archaeological site that was settled during the Early Bronze Age in the southeastern part of Israel’s Judean Shephelah (lowlands), a little over 20 miles southeast of Ashkelon, the archaeologists encountered countless ruddy molehills dotting the straw-covered hill.
As part of a larger study of how archaeological material — specifically potsherds — reached the surface of the site from below, they hypothesized that some of the debris was left there by the burrowing species Nannospalax ehrenbergi (indigenous to the Middle East, including Egypt, Israel, Jordan, Lebanon, Libya, and Turkey).
While encircling the site to remeasure its size, Prof. Avraham Faust, the head of the Tel ‘Eton Excavations, and Dr. Yair Sapir (then Faust’s doctoral student) noticed a large concentration of pottery sherds in a few molehills to the northeast of the ancient mound. This puzzling cluster of sherds was found in a part of the site that had been surveyed in the past, but no evidence of human settlement had then been discovered there.
After briefly examining the area, the researchers wondered if the concentration of sherds in the molehills hinted that there may have indeed been a substantial occupation in this low, flat area. They devised a detailed study to test this theory, and later excavated the area based on findings from the analyzed molehills.
“The bottom line was quite clear,” said Faust. “The mole-rats brought up material from below, and hence, systematically examining molehills can be a good indication for human activity.”
It’s such a brilliantly simple idea that the archaeologists were positive it must have already been scientifically tested.
“Initially, we found it hard to believe that nobody suggested it, so we did not dare say that we are the first. We were quite sure that someone had already done it,” said Faust.
In fact, when publishing their innovative idea, Faust and co-author Sapir cautiously called their 2016 paper for the Advances in Archaeological Practice quarterly “Utilizing Mole-Rat Activity for Archaeological Survey: A Case Study and a Proposal.”
The word “proposal” in the subtitle indicated, said Faust, that the researchers thought they were proposing something new, “but we were afraid to say so explicitly” for fear it had already appeared in the field’s literature. Today, two years after its publication, there is no indication that the idea had ever been systematically utilized in the past.
“I daresay we are the first,” said Faust.
Granted, there have been researchers who had utilized data gathered from studying rodent activity, said Faust.
“While some studies researched the activity of mole-rats systematically in the site they worked on, this was never suggested as a survey method. They simply took advantage of the finds to know more about their site,” said Faust.
What Faust and Sapir propose is another animal altogether.
“Identifying ancient sites is one of the main goals of the archaeological survey. Still, ‘pedestrian’ surveys [when a number of people walk across the landscape, looking for above-surface remains] miss many sites,” he said.
“In the US and Europe, where the landscape is overgrown and visibility is limited, archaeologists often use shovel tests [a systematically spaced series of circular or rectangular holes that are dug, usually to a depth of about 20 centimeters, or 8 inches, in search of man-made debris] as a means of identifying unknown sites,” said Faust.
All of this takes considerable time, manpower, and cost.
A systematic examination of rodents’ back-dirt mounds, including those of other species, such as prairie dogs, armadillos, gophers, porcupines, and rabbits, “can be an effective method — faster, cheaper, and more efficient than pedestrian surveys or shovel tests — of discovering unknown sites even in regions with good visibility,” he said.
“In a sense, the rodents do much of our work,” said Faust.
There’s a whole world down there
It was while completing a much more extensive study on site formation processes in Tel ‘Eton, the subject of Sapir’s PhD dissertation, that the team looked into the effect of “bioturbation,” animal’s disturbances and reworking of subterranean soil and objects. Specifically, they looked at the movement of archaeological artifacts — mainly of potsherds.
What they discovered in analyzing the molehills was like hitting the jackpot.
In his doctoral dissertation, “Site Formation Processes at Tel ‘Eton and Its Surrounding,” Sapir writes: “Many people treat archaeological sites as time capsules that were preserved unchanged below the surface. This, however, is hardly ever true.”
Especially, one could add, at a site infested with mole-rats.
Covered with light gray fur and sporting a mouthful of protruding sharp teeth that cry out for orthodontia, the aesthetically displeasing mole-rats are fossorial (or “digger”) animals whose lives are led primarily underground.. As indicated by their full name — the Middle East blind mole-rat — these 100-200 gram creatures cannot see and have sunken vestigial eyes. Interestingly, they also do not have real earlobes and their ears are found deep inside their heads in an adaptation against dust.
Their raison d’etre is digging, and they are rather systematic about it.
“Aside from the burrows it also has a home that’s built in a fantastic architecture, especially those of females that are about to give birth: There’s a children’s room and a bathroom and a pantry. And this pantry isn’t just piles of this and that, it’s all neatly organized,” Prof. Aaron Avivi from Haifa University’s Institute of Evolution told Haaretz in a 2013 article discussing the rats’ amazing cancer-resistant properties.
“The children’s room is built of all kinds of twigs. The nursing female mole-rats make a pergola roof and cover it with earth and put all kinds of grass in there,” he said.
The burrows, feeding tubes, and nests make for a lot of displaced earth, however — mounds that weigh two to three kilos (4.4 to 6.6 lbs), according to Avivi. For an archaeologist, that’s a whole lot of disruption — but also an opportunity.
“They are part of nature. Still, they are clearly causing much harm. There is no way to control or limit the damage they are causing, but we suggest that besides the harm, there is also some good, and that we could take advantage of this good,” said Faust.
According to Faust, “the original aim of studying mole-rats [was] to understand, how does material from deep down reach the surface?”
Discerning the numerical density of the sherds in the molehills in the plain below the mound led them to realize that systematically examining molehills may provide a tool to identify unknown sites — not only at Tel ‘Eton.
To test if back-dirt analysis should be included in international archaeologists’ methodological toolboxes, the researchers devised a controlled study, and compared the number of sherds in the molehills in a number of different “units.” They chose sites on the mound itself, in the area they suspected to be a lower city, as well as in a series of spots in nearby hills and valleys — places in which no settlement was suspected.
The field research took place during the 2014 excavation season (supplemented in 2015), and the team examined 229 molehills on the hill and its surroundings. In their paper, Faust and Sapir state that “the molehills were selected during pedestrian survey in an attempt to arrive at a uniform coverage of each examined unit.”
To maintain samples of approximately the same volume, they chose to only examine the back-dirt hills from feeding tunnels, which generally go to about 40 centimeters deep, as opposed to the deeper nesting back-dirt piles, which were of more varied sizes. All material was sifted through a 5-millimeter mesh and every sampled molehill location was recorded by GPS.
In the laboratory, the sherds that were larger than 5 millimeters (0.2 of an inch) were counted and measured. Archaeologists are unable to date such sherds, said Faust, but their numeric density is revealing. A large number of sherds can point to indications of human activity hidden underground; a smaller number points to the absence of such activity in the area.
They marveled at the efficacy of the system.
“The finds were very instructive,” said Faust. “The number of sherds in most units outside the mound – with one exception – was very low, but their number in the area suspected to be a lower city was similar to that on the mound.”
Faust and his team therefore determined that the suspected settlement was worth further investigation.
“Using this method we discovered human occupation in the plain below the mound [outside the tel, in an area not known to be settled],” said Faust. “Initially, we searched for more, aboveground remains, but in addition we carried out a small dig to test it.”
In the summer of 2015, the team excavated a single 5 meter by 5 meter square in the area of the conjectured city.
“The excavations revealed substantial cultural remains, including parts of a well-preserved building, with a few phases (dated to the late Iron Age), along with diverse accumulations and surfaces within the structure and without it,” they write in a postscript to the paper.
But the molehills produced additional finds: As the researchers analyzed the anomalous extra-mound survey unit which had produced human cultural remains, they also discovered a proliferation of “slags,” material that is a byproduct of smelting.
“Such slags were not found elsewhere, and this concentration is not likely to be a coincidence… We tend to attribute these finds to a possible workshop,” they write in the paper.
Faust carefully emphasizes that even the lack of molehills, not only a paucity of sherds in the mounds, could be important. No mole activity at all could, for example, indicate ancient subterranean walls or structures that prevented burrowing.
At Tel ‘Eton, the lack of molehills in one area led the team to suspect that there is a siege ramp there. This is a question now under study.
Immediate practical applications
For his part, Sapir has personally already informally tested the methodology elsewhere.
The summer after the team had completed its analysis of the molehills, Sapir and his mother, father, and brother went on a family roots tour to Holland. While in the Westerbork concentration camp, where a portion of their family had perished during the Holocaust, his mother lamented the lack of remains from the camp’s original structures.
Sapir noted that at every spot in which there had been a prisoners’ shack, there was a low dirt platform.
“My mother wanted to take a physical reminder from the site, like a stone, but like in the majority of Holland, everything was covered in earth and grass, and there weren’t any stones on the surface,” he said.
“Automatically, I recognized on one of the earth platforms a mound from a local burrower. I rummaged around in it, and immediately found a number of little rocks and charcoal which had apparently survived from the original shacks,” said Sapir.
In quickly retrieving debris from the site’s grim past, Sapir again proved the new archaeological methodology has far-reaching — if perhaps unexpected — applications.