Holes in the head

By John Bonifield, CNN

Published 7:51 AM ET, Mon August 15, 2016
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An ancient surgeon in Peru probably used a sharp tool to carefully groove the perfect circles in this Incan skull. Healed bone around the edge of the holes indicates the patient was alive during the surgery and probably survived. Scholars can't explain the purpose behind the mysterious multiple openings. Harvard University Press
The deep, straight cuts in this Peruvian skull were made by rocking a blade back and forth. Their varying placement suggests the surgery was poorly executed and unsuccessful. Harvard University Press
The half-circle broken out of this Peruvian skull was possibly caused by a slingshot stone. A triangular surgical hole extends from the fracture. Harvard University Press
A surgical hole in this skull was started and then stopped. The linear criss-cross cuts are unfinished, perhaps because the patient, a Peruvian child, didn't live long enough for the surgery to be completed. A smashed and broken section of injured bone is visible inside the attempted opening. Harvard University Press
A stone blade scraped through layers and layers of bone to create the gaping hole in this skull. The operation was among the first of its kind ever performed in the Americas, about 2,400 years ago. Through the opening, a prehistoric Peruvian surgeon could clean a head would or examine the brain for bleeding. Harvard University Press
This skull is another example of early cranial surgery in Peru. Long-term survival rates were only 40%. Fewer than half the patients made it. Harvard University Press
The hole in this Peruvian skull shows the different layers of bone a surgeon scraped through to create the opening: an outer layer, a spongy middle layer and a thin inner layer. Openings this large often removed all evidence of why a surgery was performed. Harvard University Press
Rectangular holes like the one in this Peruvian skull could be made rapidly by rocking a sharp tool down through the bone. The method was faster and riskier than scraping or grooving a hole, since it increased the chances of tearing directly into the brain with the blade. Harvard University Press
It's unlikely this Incan patient had four head injuries, each requiring surgery. The hole is another example of unexplained multiple openings. Survival rates for prehistoric cranial surgery in Peru greatly improved over the course of two millennia. In Incan times, 500 to 700 years ago, nearly 80% of patients survived. Harvard University Press
The hole in this skull was made by drilling a circle of smaller holes and then cutting away the bone between them. Of the four techniques used by Peru's ancient surgeons, it's the most similar to modern surgery. Today, to create a hole, often surgeons drill four smaller holes in a rectangle and then saw away the bone between them. Harvard University Press