March 23, 2007 — Determining the daily activities of prehistoric people is difficult without written records, but scientists have figured out a way to identify individuals who often engaged in intense water-related activities, such as diving, surfing and fishing.
The clue is in their ears.
According to a paper accepted for publication in the American Journal of Physical Anthropology, abnormal ear canal bone masses, called auditory exostoses, can be linked to aquatic activities. Like a sort of skeletal tattoo, the masses mark the remains of some early individuals.
"Auditory exostoses can develop when the ear is exposed to cold water (below around 66.2 degrees Fahrenheit) and/or to warmer water chilled by the action of cold atmospheric temperature and/or strong winds," explained Sabine Eggers, who worked on the study with Célia Boyadjian and Maria Okumura.
Eggers, a researcher in the Biological Anthropology Laboratory in the Department of Genetics and Evolutionary Biology at the University of Säo Paulo, Brazil, said that the "external region of the ear canal responds to chill with increased blood flow and inflammation."
Bone tissue then produces new cells and, over time, this can lead to bony outgrowths that may be helpful for scientific study, but can cause hearing loss in the subject.
The researchers analyzed 676 skeletons dating from 5,000 years ago to more recent times from 27 coastal and inland native Brazilian groups. As predicted, few inlanders possessed the bone masses, but many coastal groups had them. Skeletons from only one region, the southern part of the state of Santa Catarina, presented differences between the sexes, suggesting that women usually, but not always, went out on the water as men did.
Other clues hint at what the coastal dwellers did above and under water.
"They certainly fished habitually, since fish was their main source of protein," said Boyadjian. "We know that from the fish remains scattered throughout the sites, and the chemical analysis (stable isotopes) from the human bones."
Mollusk shells from shellfish that they could only obtain by diving indicate they frequently swam underwater, while hooks and weights suggest they fished from shore and boats too.
They probably surfed as well.
