The skeleton showing the violent life of the ice age

It was a group of divers who made the startling discovery in 2007. In an underground water-filled cave system deep inside the Mexican jungle, they found plenty of prehistoric animal bones.

Among the remains, 30 meters below the surface, they also found the skeleton of a human. The legs were 13,000 years old, one of the oldest finds on the American continent.

It turned out to be a skeleton of a girl aged 16. She was named Naia after the Najads in Greek mythology and she would prove to be a gold mine in the research of the first Americans.

Researchers have compared Naia's DNA with 11,000-year-old skeletons from Asian immigrants in Alaska and with today's indigenous peoples in North and South America.

The results indicate that she and all other indigenous people in America are descendants of a group of people living in Beringia - a land bridge that linked Siberia and Alaska 25,000 years ago.

That population, in turn, was a composition of people who migrated from different parts of Asia.

In the past, it has been believed that the spread to the rest of America was via an inland ice cover that covered current Canada.

But recent findings have shown that the very first Americans were likely to travel south by boat along the Pacific coast. Most recently in a study in Science.

And Naia had lived a hard life, characterized by constant movement in search of food.

The muscle brackets on the skeleton show that she had the leg strength of a modern 35-year-old man even though she was still a teenager.

Her teeth show signs of starvation during parts of the year. The researchers interpret that her tribe had come to South America quite recently and had not learned how to support themselves all year.

Her world was full of violence. Many skeletons from this era bear traces of strife, and Naia is no exception.

The researchers also found damage to Naya's pelvic bone, which shows that she was forced to grow up early.

"She had given birth to an age when her skeleton was not fully developed for birth," says anthropologist Vera Tiesler at Yucatán's Free University.

Childbearing was a major danger in the Stone Age. Many women died in childbirth - and Jim Chatters believes it was another cause of the violence.

- The women died at the age of 20, the men when they were thirty. It must have created a women's deficit, and fierce competition among men, he says.

The skeleton also tells of what happened the day Naia died. She has an unbridled pelvic fracture, which most likely occurred during her last minutes of life.

Today, the cave system where Naia was found is filled with water, but 13,000 years ago the sea level was much lower and the Yucatan Peninsula, where she found was an extremely dry place during parts of the year.

The researchers believe that she had gone deep into the cave system in search of water. Maybe she got lost in the dark, and fell 30 feet down the hole where she was found. She was probably injured in the case and died almost immediately.

Want to know more about the first Americans and how it went when divers found Naias skeleton? See the program The Girl from the Ice Age in the World of Science on Monday, September 9 in SVT2, at. 20:00. The program can also be viewed from Sunday 8 September on SVT Play.