The researchers said the reason for the presence of atherosclerosis among all four populations is unknown. Their diets were quite disparate, as were the climates in which they lived, they wrote.
One common factor was the use of fire for warmth and cooking, the researchers said. "Although cigarette smoking was not part of these four ancient populations, the need for fire and thus smoke inhalation could have played a part in the development of atherosclerosis," they wrote.
Additionally, all four populations lived at a time when infections were common and a major cause of death. "Chronic infection and inflammation may have promoted the inflammatory aspects of atherosclerosis," they wrote.
A limitation of the study was the use of calcification as a marker of atherosclerosis since there was no pathological confirmation that the calcifications represent atherosclerosis. Still, arterial calcifications on imaging studies in modern patients are deemed characteristic of clinical atherosclerosis, the researchers noted.
Moreover, "the location of the disease was similar to what we see in our patients," Thompson said.