Discovery of skulls reveals 6,000-year-old mystery

More than 140 years ago, dock workers made a discovery that would take generations to explain - 23 human skulls buried alongside the remains of prehistoric animals.

The extraordinary haul included more than 60 pairs of red deer antlers, aurochs skulls and two dugout canoes, revealing that the area had been a site of human activity for thousands of years.

When the Albert Edward Dock opened in Preston in 1892, it was the largest single dock in England.

But beneath the Victorian construction lay a much older story — one involving prehistoric communities, an Anglo-Saxon woman who died violently and a mystery over how so many human skulls came to rest in the same place.

Victorian researchers speculated that the 23 human skulls belonged to Bronze Age people who had lived beside the Ribble, but later research has shown the remains came from a much wider period.

A study using radiocarbon dating found that the skulls came from different periods, from the Neolithic to the early medieval period

Researchers concluded that the skulls may have entered the River Ribble at different times before being carried downstream and deposited where the water slowed.

For decades, little was known about who the skulls belonged to or when they had lived.

More recent research by the University of Lancashire and Liverpool John Moores University, using carbon dating, revealed that the remains came from a period spanning 3800 BC to 1000 AD.

"I wanted to find out more about them," said Emma Heslewood, who was museum curator at The Harris between 2000 and 2014.

The oldest male discovery was a skull dating back to 3520-3330 BC. He would have been about 40 years old when he died.

Another, belonging to a woman, has been dated to 3820–3640 BC.

Carbon dating is a method used to determine the age of organic material such as wood, bone and charcoal.

Developed in the late 1940s, it works by measuring the amount of radioactive carbon-14 remaining in a sample.

Living organisms continually exchange carbon with their environment. When they die, this process stops and the carbon-14 gradually decays.

Because carbon-14 decays at a known rate, with a half-life of about 5,730 years, scientists can estimate how long it has been since an organism died.

Radiocarbon results are then calibrated to account for fluctuations in atmospheric carbon-14 levels over time.

Carbon dating of the skulls showed they came from a remarkably wide range of periods, spanning more than 6,000 years.

"The oldest find was from the Neolithic period, also known as the Stone Age," said Emma Heslewood.

"But they also found the human skull of an Anglo-Saxon woman. What was even more remarkable was that the skull had evidence of a violent death.

"This woman died as a result of a blow to the back of the head and a sword cut through her face and ended up in her eye socket.

"She would have lived some time between 400-700 AD."

The archaeological research puts the Anglo-Saxon woman's skull later, at around AD 680–890, and identifies a sharp cut above the eye that probably resulted from a sword blow, along with another sharp cut across the top of the skull.

The discoveries raised an obvious question: why were so many human skulls found together?

Earlier theories suggested the remains could have been evidence of a massacre or mass burial. More recent research has offered a different explanation.

During construction of the dock, the River Ribble was diverted and the area excavated.

"One of the questions we had was how did so many skulls end in the same place?" said Heslewood.

Researchers studying the remains have considered that skulls could have entered the river at different times and places before being carried downstream and deposited where the water slowed.

As well as the human remains, archaeologists found red deer remains, including dozens of antlers.

"Wild deer are known to migrate in large numbers, so they may have tried to cross the river and maybe got caught out," said Heslewood.

The excavation also uncovered skulls belonging to aurochs, an extinct wild ox that were ancestors of modern domestic cattle.

"They are huge, up to 1.8m tall. They originated in Asia. These animals would have been grazing in Lancashire," according to Heslewood.

Aurochs became extinct in Europe, with the last known individual dying in Poland in 1627.

There were also two dugout canoes, made by hollowing out tree trunks. The boats are thought to date from prehistoric times, although at least one may have remained in use into the medieval period.

The discoveries were preserved and many are now held at The Harris, which has more than 1,000 items associated with Preston Dock in its wider collection.

Despite the remains being uncovered more than 140 years ago, research continues.

The Harris has worked with researchers to investigate the skulls further, including genetic analysis, in an effort to learn more about the people whose remains were recovered from the dock excavations.

"The Francis Crick Institute is currently conducting analysis on the skulls," said Gemma Burns, history curator at The Harris museum.

"They are carrying out DNA testing and carbon dating on the skulls so we can better understand the lives of the people whose skulls they are."

The discoveries continue to attract public interest and a talk on the Preston Dock archaeological finds at The Harris is now sold out.