How did ancient Egyptians end up with an affluent 'modern' disease?
The discovery of hardened arteries in ancient remains of working people has scientists rethinking the causes of atherosclerosis. Michael Russell reports.
For years, researchers assumed that atherosclerosis – a hardening of the arteries that leads to heart attack and stroke – was a modern affliction caused by high-fat diets and a lack of exercise. But according to a new study, the disease can be traced back to ancient Egyptians – and working class ones at that.
Michaela Binder, a bioarchaeology PhD student, and Charlotte Roberts, an archaeology professor, both of Durham University in the United Kingdom, published their findings in the March issue of the International Journal of Paleopathology.
Atherosclerosis occurs when lipids and fats stick to the inner walls of an artery. Immune cells try to dislodge them, but instead add to the pile-up, forming plaques. The cells ooze calcium, and over time the calcium grows like stalactites in a cave, eventually forming a lattice. When a person dies, the cells, lipids and fats waste away, but the calcium latticework survives and maintains the shape of the plaque. These petrified plaques are so hard that they survive as strangely curved little bony chunks in skeletons and can provide evidence of ancient atherosclerosis.
The most ancient known examples of petrified plaques come from a 1931 study by Roy Moodie, published through the Field Museum of Natural History in Chicago. He found pieces of calcified plaque in 5,000 to 8,000-year-old mummies from Peru and Egypt. Scientists thought that they shared our plaque because they also shared our affluent habits – eating fattier foods and getting less exercise.
'People tend to think of atherosclerosis as a disease of the affluent – we’re overfed, under-exercised. But now we’re starting to think that’s less true.'
But those mummies represent society’s elite. Binder and her colleagues wondered about the rank and file members of ancient times. Would their remains also show plaque? To find out, they studied non-mummified skeletons from Sudan that date to between 1300 and 800 BCE, when the ancient Egyptian New Kingdom dominated northeast Africa. The site was particularly useful to Binder’s team because it featured both cemeteries and a settlement – a rare find in archaeology – that allowed researchers to study how these ancients both lived and died.
They identified five different skeletons and looked for irregularities in the skeletons, including out-of-place or extra pieces of bone-like material. They carefully collected small chunks of bony material that lay near the chest of three of the skeletons, and near the femoral arteries and the pelvises of the other two. But were they really bits of plaque or just odd bone fragments? There were two tell-tale signs. First off, the edges of the fragments were smooth. If they’d been bits of skeleton, they’d be fragmented from where they broke off bones. They also had a different texture and a slightly different colour than bone.
But the clincher came from measuring the size and curvature of the fragments. They found that they corresponded almost perfectly to the arteries in which the pieces would have formed. For example, the three samples found near the chests of the skeletons were the same diameter – between two and 2.5 millimetres – as the typical coronary artery.
Binder’s findings are significant because finding plaque in the non-mummified skeletons of commoners is unusual. “It’s pretty rare,” said Michael Zimmerman, a lecturer of anthropology at the University of Pennsylvania, commenting on the findings, who blamed the disruption to a skeleton often caused when they are discovered. But Binder started this study explicitly looking for the calcified plaque pieces, so she and her team took extra care not to lose the plaque in the shuffle.
So what caused atherosclerosis in the commoners of ancient times? Today’s risk factors include a high-fat diet, meat consumption, poor dental hygiene and smoking. The ancient poor may have experienced some of the same– especially smoke from wood fires and pottery kilns. “People tend to think of atherosclerosis as a disease of the affluent – we’re overfed, under-exercised,” said Michael Autieri, a professor at the Temple School of Medicine in Philadelphia, who was not affiliated with the study. “But now we’re starting to think that’s less true, since inflammation, pollution and infections cause atherosclerosis too.”
In addition to providing insight into the history of atherosclerosis, Binder’s research demonstrates the importance of handling skeletons with care. Zimmerman hopes that other archaeologists who read the research will be more careful when excavating skeletal remains in the future.
“The study shows the importance of studying skeletons,” Binder said. “It’s not just studying old dusty bones.”