Now, scientists have discovered a case of ritual decapitation in Brazil that dates back about 9,000 years.
"This is the oldest case of decapitation found in the New World," Strauss told Live Science.
The scientists investigated an environmentally protected tropical region in east-central Brazil known as Lagoa Santa, which means "Holy Lake" in Portuguese. The area, which is covered in savanna-type vegetation as well as forests, was explored heavily in the 19th century by researchers looking for evidence of interactions between prehistoric humans and giant animals, such as saber-toothed cats and ground sloths.
The scientists focused on a site called Lapa do Santo, or "saint's rock shelter." It was here that the researchers previously found the oldest evidence of rock art in South America, which included pictures of penises, engraved on the bedrock there, that are about 9,400 years old.
Excavations at Lapa do Santo revealed signs of human occupation dating back about 12,000 years. Stone tools and animal bones found at the shelter suggest the prehistoric groups that lived there subsisted on plants they gathered and small and midsize animals they hunted.
In 2007, the researchers discovered 9,000-year-old fragments of human remains at Lapa do Santo, including a skull, jaw, the first six vertebrae of the neck and two severed hands. The bones were buried about 22 inches (55 centimeters) below the surface, under limestone slabs, which suggests they were part of a deliberate ritual entombment, the researchers said.
The amputated hands were laid palm-side down over the face of the skull, with the left hand pointing upward and covering the right side of the face, while the right hand pointed downward and covered the left side of the face. Until now, only relatively simple burials had been uncovered in Lagoa Santa, Strauss said.
In addition, the disembodied heads found in South America were typically discovered in the Andes mountain range, suggesting that decapitation began as an Andean practice. This new finding suggests that ritual beheading may have started elsewhere, the researchers said.
It remains unclear why this ritual decapitation at Lapa do Santo took place. The chemical nature and physical features of the bones suggest they came from a member of the group that lived there, the researchers said, meaning the body likely was not a war trophy of an outsider. Instead, the people at this site may have used these remains to express their ideas regarding death and the universe, Strauss said.