Hair Reveals Ancient Peruvians Were Stressed Out
Remains of an individual buried in Cajamarquilla, Peru. The hair from this and other remains showed high levels of a stress hormone. Dr. Andrew Nelson
People in the past were very stressed out, suggests a new study that found high amounts of a stress hormone in the hair of Peruvian individuals who lived between 550 A.D. and 1532.
The study, accepted for publication in the Journal of Archaeological Science, is the first to detect the stress hormone cortisol in ancient hair. Cortisol is produced in response to real and perceived threats. After its release, the hormone travels to nearly every part of the body, including to blood, saliva, urine and hair.
It now may be possible to determine not only how ancient people behaved, but also how they felt.
"Combined with archaeological reconstructions of past communities and societies, and traditional bioarchaeological approaches to understanding stress, health and well-being, research like this will significantly enrich our ability to reconstruct ancient life histories, and let us explore individualized experiences of people who died hundreds or even thousands of years ago," lead author Emily Webb told Discovery News.
Webb, a University of Western Ontario anthropologist, and her team measured cortisol in hair from 10 individuals buried at five different sites in Peru: Cajamarquilla, Leymebamba, Puruchuco, Tucume and Nasca. The researchers also found the stress hormone in hair from early Ontario residents, ancient Nubians and early Egyptians, but the Peru residents were the focus of this study.
Hair grows at a rate of about 0.4 inch per month, so depending upon the individual's hair length, the researchers were able to trace stress levels up to 27 months before the Peruvian people died.
Just before death, their stress levels were predictably high. But before their demise, some people experienced abrupt rises and falls of cortisol, which could be due to many different reasons.
For example, Webb said the stress could be because of "food availability, drought conditions and nutritional stress," along with reaction to actual or perceived threats "to physical or social integrity, i.e. to health, safety and well-being."
While the stress levels of these Medieval Peruvians were higher on average than levels measured for today's individuals, Webb indicates that the comforts of modern living may not be able to erase human stress.
"A society serves as a protective buffer, and while our society effectively protects us from, for example, extreme year-to-year differences in food availability, as individuals, we still experience considerable stress in our lives for other reasons," she said.
Her team's findings may help to explain why hardening of the arteries (atherosclerosis), associated with stress and other risk factors, was found in 3,500-year-old Egyptian mummies.
University of California at San Diego School of Medicine researcher Michael Miyamoto, who led that study, discovered the highest amount of atherosclerosis in Lady Rai, a nursemaid to Queen Ahmose Nefertiti. Lady Rai died between the age of 30 and 40 at around 1530 B.C.
Webb and her colleagues are now hoping to pinpoint what might have caused the detected stress in the early Peruvians. This may be possible, she said, since nitrogen and carbon isotopes present in hair permit reconstruction of ancient diets and certain physiological and metabolic states.