The sun and stars may have served as critical references for a startlingly diverse range of ancient builders who constructed chambers to hold the dead and other religious shrines.
The orientation of thousands of Neolithic tombs erected across Europe and Africa around 10,000 B.C. were apparently built to face the rising sun, securing the sun's importance in various human cultures across three countries, two continents and the Mediterranean islands, according to one astronomy historian.
"I think all these cultures looked on the sunrise as a symbol of hope," Michael Hoskin, a historian of astronomy who conducted a study, said in an e-mail interview. "The customs of structure of the tombs vary hugely from region to region, but the patterns of orientation are very similar."
Hoskins, a historian of astronomy at Churchill College in Cambridge, England, also found that the Bronze Age sanctuaries of one Spanish island could have once served as healing centers, though the lack of any written record of the region makes it impossible to know for sure.
"That they were sanctuaries, whether for healing or otherwise, is clear by the statues found there and also from the mass of bone fragments and sacrificed animals that litter them to this day," he said. The sanctuaries, he added, may have been built with the constellation Centaurus in mind. In Greek mythology, the centaur Chiron taught the god of medicine.
Hoskin presented his findings April 2 at the National Astronomy Meeting of the Royal Astronomical Society at England's Open University.
Tombs of the rising sun
The sheer number of Neolithic tombs built with sunward-oriented entrances suggests, if nothing else, that the sun played an important role that coincided with a person's death, researchers said.
"In studies like this, in which you have a large sample of tombs, you look for trends," said E.C. Krupp, an archaeoastronomer and director of the Griffith Observatory in Los Angeles, adding that it's amazing such structures can be identified in the first place. "So not only are the dead part of the story, but the sun is part of the story too."
The Neolithic period, or the Late Stone Age, dates back between 5,000 and 10,000 years ago when humans began to take up agriculture, settling down from a more nomadic hunter-gatherer existence. Communal tombs from that era vary in construction, some using large rocks while others small, still others containing deep passages. But all, by necessity, have an entrance through which additional bodies can be deposited inside.
Hoskin spent 12 years personally cataloging the positions of 2,000 Neolithic tombs, and researching documented descriptions of 1,000 others, across France, Portugal, Spain and North Africa. The entrances of nearly all, he said, appeared to have built to face the rising or climbing sun at some point during the year.
In the Alenterejo region of central Portugal, for example, every one of the 177 tombs measured by Hoskin faced sunrise, usually during autumn and early winter, with a sharp cutoff at the winter solstice.
"All the evidence is consistent with their having aligned their tombs with sunrise on the day when building started, which is exactly what we know happened commonly with Christian churches," Hoskin said. "The churches face the rising sun as a symbol of Christ rising from the dead. No doubt the Neolithic people saw the rising sun as a symbol of hope of afterlife."
The only exception were some tombs around the small French town of Fontvieille, where the monuments were built facing sunset, unlike any others found, Hoskin added.
In a separate study, Hoskin believes he's found some evidence suggesting that the shrines built on the Spanish island of Menorca around 1000 B.C. were centers for healing as well as religious prayer.
His survey of about 30 "taulas," sanctuaries built during the Menorcan Bronze Age, found the shrines consistently built with a clear view of the south, some looking out over the ocean while others sit above open plains. In 1000 B.C., Menorcan worshippers would have been able to see the Southern Cross and Centaurus constellations in the night sky, and if they had a Centaur mythology similar to the Greeks, it's possible the sanctuaries were viewed as a place to seek healing.
"We know that the constellations as viewed by various peoples of the Middle East and Mediterranean had a great deal in common. … There was almost a common pool of ideas with local variants," Hoskin said. "We do not know much about the constellations as viewed by the Menorcans, since they were not literate."
But the healing center theory would explain not only the orientation of the shrines, but also the presence of bronze hoofs in the ruins as well as an Egyptian statue that bears the hieroglyphic inscription "I am the god of medicine."
Hoskin said nothing notable in the sky can be seen from the door of these sanctuaries today, due to the precession of the Earth on its axis.
Even with a written record, Krupp said, it would be difficult to say for certain what shrines like those of Menorca were used for.
"It implies a certain social organization in the commitment to build the construction of these monuments, as well as a system of celestial observation," Krupp said. "But when you find an astronomical alignment, even you feel very confident about its intent, its real purpose may not have involved that at all."