Archaeologists working near an Iron Age house near Cambridge were amazed to unearth a vast trove of frog skeletons. Why more than 8,000 bones were piled up and preserved is a prehistoric mystery.
They were all recovered from a single 14 meter long ditch, right next to the site of an Iron Age roundhouse at Bar Hill, where there was a settlement during the Middle and Late Iron Age (400 BC – 43 AD). The discovery was made by the Museum of London Archeology (Mola) Headland Infrastructure, who were conducting excavations as part of the Cambridge to Huntingdon National Highways A14 road improvement programme.
While it’s not uncommon to find frog bones at ancient sites, archaeologists are amazed at the sheer quantity of those unearthed at Bar Hill.
dr Vicki Ewens, chief archaeozoologist at Mola – a specialist in ancient animal bones – told the observer: “In my experience, we mostly work on London sites, we don’t get that many frogs. It’s extraordinary that so many bones come out of one ditch.”
Noting that these bones mostly belong to the common frog and common toad, species found in garden ponds across the country, she said, “We also have possible evidence of pond frogs, which is exciting… That’s something we usually do.” not found archaeologically.
“During my research, I only found two Saxon sites, each with individual bones. It is a frog found only in East Anglia that became extinct in the 1990s, possibly due to habitat loss, but has recently been reintroduced.”
Being prehistoric, it’s difficult to explain, although ancient civilizations – including the Egyptians, Mesopotamians, Greeks, and Romans – all saw the frog as a symbol of fertility, among other things.
It is unlikely that these amphibians were eaten by the residents of the settlement. The archaeologists say that while there is evidence of amphibian consumption in Stone Age Britain, these bones show no cuts or burn marks. However, if the frogs had been boiled, it might not have left a mark.
Evidence of charred grain found near the site suggests its residents processed crops that would attract pests such as beetles and aphids, which are known to be eaten by frogs. Perhaps the frogs were drawn to the area by the promise of food, archaeologists suspect.
Other possible explanations are “a prehistoric frog tragedy”. The archaeologists say that in the spring, frogs move in large numbers in search of breeding waters, and these may have fallen into the ditch and become entangled.
According to one hypothesis, the unusual death toll could also have been caused by hardiness. While winter frogs sometimes hide in the mud, extreme cold can kill them, and perhaps they fell victim to a particularly harsh winter.
Alternatively, they could have contracted an illness, just like in the 1980s when British frogs were devastated by a ranavirus.
It is unclear how deep the ditch was. The field team dug about a meter through top and bottom soil to reach it. Only small amounts of household rubbish were found on the site, including shards of Iron Age pottery.
The amphibian bones were among a variety of finds, from artifacts to human remains, in around 40 excavations that took place between 2016 and 2018, covering 234 hectares. The analyzes are still ongoing, although the excavations have now been completed.
Ewens has spent the past two years studying the bones of animals, including cattle. Once all the studies come together, it is hoped they will shed new light on life as it was thousands of years ago and discover the reason for the deaths of so many amphibians.