Atherosclerosis is what happens when your arteries fill up with layers of fat and white blood cells. It's a disease of chronic inflammation that increases your risk of stroke and heart attack. It's also a disease we tend to associate with the modern era — commonly cited risk factors include cigarette smoking, obesity, and stress. But there are some signs that we may not have a great handle on what actually causes atherosclerosis. That's because ancient mummies, from all over the world, have shown signs of the disease. It's unclear what this means at this point — for instance, just because ancient people didn't light up a Marlboro from time to time doesn't mean they weren't exposed to smoke and particulate matter from indoor cooking fires. But it's fascinating to see a disease of modernity affecting the past.