Pembroke Castle has been a center of power for centuries. It was the birthplace of Henry Tudor, father of Henry VIII, and is one of the best preserved medieval strongholds in the country, with a maze of passageways, tunnels and stairs, as well as a huge gatehouse tower. Scientists have discovered that the fortress also hides a surprising secret. A cave known as Wogan Cavern, which lies directly beneath Pembroke Castle, has been discovered to contain a wealth of prehistoric material, including ancient bones and stone tools left by early Homo sapiens and possibly Neanderthals.
These remains will provide important information about the settlement of Britain in prehistoric times, say scientists, who began their first major dig of the year at Wogan last week. Work on the site in the coming years should provide answers to major puzzles about prehistoric Britain, including the end of Neanderthal occupation some 40,000 years ago.
Early finds at Wogan include a wide range of fossils, including mammoths, reindeer and woolly rhinos, as well as the remains of a hippopotamus, a species that last roamed British waters 125,000 years ago. Archaeologists have also discovered that much of the cave floor is covered in a layer of stalagmite that has preserved the soil, bones, proteins and DNA beneath.
“The site has fantastic potential,” says Prof. Chris Stringer of the Natural History Museum, London. “It is the best prospect we have of providing new material that can help us discover how Neanderthals lived in Britain and how they were replaced by Homo sapiens.”
One of the problems scientists are trying to solve is whether or not Neanderthals interbred with Homo sapiens in Britain, as they did in other parts of the world. For good measure, they also want to know whether the two species coexisted or whether they replaced each other in successive waves. “Wogan Cavern offers us the prospect of finding material that will give us clear answers to these questions,” Stringer said.
The excavation leader, Dr Rob Dinnis from the University of Aberdeen, said: “We have already shown that preserved layers of bone, stone tools, DNA and other material dating back at least 40,000 years lie beneath Pembroke Castle, while the hippopotamus remains we have found suggest we could push this back to 125,000 years. If so, this is the perfect resource for studying the transition between Neanderthals and modern humans, which probably took place in Britain around 45,000 years ago.”
In recent decades, scientists have struggled to investigate this intriguing aspect of settlement in Britain, as they have faced a critical problem affecting many important prehistoric sites in Britain. In many cases, these have been stripped of all their sediment, rocks and other materials and thus cannot be studied using the arsenal of modern technologies that scientists developed in the 20th century.
“In the past, when Victorian or Edwardian archaeologists found remains of Neanderthal or early Homo sapiens at a site, it was usually cleared of all the sediment and bones contained within,” says Dinnis. “Every last bit of archaeological material was collected or, worse, thrown away. It has made modern research at these sites very difficult.”
A classic example of this fossil purge is provided by Gough’s Cave, in Cheddar Gorge, where the remains of several ancient people had been excavated in Victorian times before the cave was cleared of all its sediment. “In the late 1800s, more than 500 tons were cleared in a few weeks because the cave owners were interested in uncovering the stalagmite formations there and turning it into a tourist attraction,” Stringer said.
“So they just walked out with wheelbarrows full of stuff and no one knows where they dumped it. It was a tragic waste of critically important material that we could still exploit today – if only we knew where it was being thrown away.”
Other sites that have shown evidence of ancient occupation but were subsequently emptied include Kents Cavern in Devon and Paviland Cave in Wales. However, no such fate befell Wogan Cavern, archaeologists say. In the Middle Ages it was walled and used as a storeroom for Pembroke Castle. Much of the floor has since remained intact and many of the wonders beneath it are believed to have been left alone.
Such impeccable preservation will ensure that any finds made in Wogan Cave are ripe for exploitation using the tools of modern archeology and paleontology. The technology of sediment DNA analysis looks particularly promising. It can be used to determine whether an individual ever lived or worked at a location simply by looking at the genetic material they left in the sediment there.
The technique was developed several years ago by scientists at Germany’s Max Planck Institute for Evolutionary Anthropology and has already demonstrated its remarkable sensitivity in a cave system known as Galería de las Estatuas, in northern Spain. Each layer of sediment in the cave system had previously been carefully analyzed and dated. Then, using sediment DNA analysis, researchers discovered that about 100,000 years ago, the population of Neanderthals, who had lived in the cave for millennia, was displaced by a completely different group of Neanderthals.
It is unclear why this replacement occurred, but the discovery clearly demonstrates the power of modern genetic analysis that, using DNA from blood and feces left by cave dwellers, made it possible to reveal population movements 100,000 years later . The hope for Wogan Cavern is that a similar analysis will shed light on the interactions between modern humans and Neanderthals in our prehistoric past – simply from the sediments in which they left their DNA.
“This technology means you don’t even have to find bones,” Dinnis said. “If you can simply find DNA in samples taken from an archaeological layer that has been accurately dated, you will find out who lived there and you will get an idea of when the cave was occupied and, more importantly, who occupied it. .
“We want to know the process of Neanderthal replacement that took place in Great Britain much better than we do now. Our understanding of it in this corner of Europe is a lot worse than elsewhere. That’s partly due to the fact that we got rid of our best locations over a century ago. The crucial point is that Wogan Cavern must give us the opportunity to put that right.”
Stringer agrees. “Britain at that time was right on the western edge of the inhabited world. So you’re basically looking at individuals struggling to survive on the edge of existence, both Neanderthals and Homo sapiens. It is a fascinating period and we want to learn much more about it.”