A publication of the Archaeological Institute of America
Curtis Runnels slipped a three-inch-long hunk of milky quartz into his pocket and figured it would make a great expedition paperweight. In 2008, the Boston University archaeologist had collected what he thought was an unworked stone just a few days into a survey for Mesolithic artifacts at the mouth of a gorge on the southern coast of Crete. But early the next day, as he sat on his patio and drank his coffee, the low sun hit the paperweight just right. "Suddenly, I could see the flake scars," he recalls. "This isn't even Mesolithic, this is much older."
How much older? The "paperweight" was actually a scraper at least 130,000 years old, suggesting that this island has a much deeper history than previously thought. Crete has been an island for five million years, so the scraper could only have been produced if a member of an ancient human species, possibly Homo erectus, first boated to the island and dropped it. Indeed, the discovery of hundreds more Paleolithic artifacts on Crete during expeditions in 2008 and 2009 pushes back the history of seafaring in the region by more than 100,000 years, causing scientists to rethink how humans traveled out of Africa. "This means that every hypothesis we've had about early humans, their migrations, their cognitive and technical abilities needs to be questioned," Runnels says. "Archaeologists looking for traces of early human migration are quite possibly looking in the wrong places."
This quartz hand-ax, which was left on the island of Crete between 130,000 and 700,000 years ago, shows that pre-modern humans boated across open seas. (Photo: Courtesy Thomas Strasser)
The Plakias Survey, named for a town near the study area, was the brainchild of Thomas Strasser, an archaeologist at Providence College who has studied Neolithic artifacts on Crete since 1988. Strasser, like many archaeologists, once believed that farmers from Europe or the Middle East first settled Crete 9,000 years ago. But in 2005, archaeologists began discovering earlier evidence of seafaring in the eastern Mediterranean, including 12,000-year-old tools on Cyprus. Other artifacts found in the region appeared to be much older, but were never properly dated. So Strasser invited Runnels to Crete to see if they could properly extend the history of Crete's first human visitors. Using a model Runnels developed to identify prime spots for Mesolithic settlements, the team picked the Preveli Gorge near Plakias because it provided access to both freshwater wetlands and caves that could provide shelter.
In June 2008, Strasser and Runnels spent their days clambering along the flanks of the gorge. Strasser says he was skeptical that Runnels's paperweight was actually a scraper, but more tools kept turning up: scrapers, cores, and blades that resembled tools from the Acheulean industry, the kind of tool kit known to have been used by Homo erectus. One day, a team member discovered a classic Acheulean hand-ax, five inches long. "That's when I was convinced we had tools associated with the first hominids to leave Africa," Strasser says.
But, he knew he needed to confirm the age of the tools based on something other than their style. Karl Wegmann, a geomorphologist now at North Carolina State University, was just completing his doctoral dissertation on the gorge. Based on the age of the sediments in which the oldest artifacts were found, he dates them to at least 130,000 years old. However, geological processes had lifted the sediments up by more than 300 feet and redeposited the tools, meaning that they could be much older. Similar artifacts from North Africa have been dated to 700,000 years ago, Runnels says. The team also found more than a thousand artifacts dating from 11,000 to 9,000 years ago, indicating a rich history of Mesolithic settlement on the island.
The area around the town of Plakias may have been inhabited as early as 700,000 years ago, possibly by Homo erectus who left behind stone tools at several sites. (Photo: Wikipedia Commons)
Strasser believes the earliest tools could have belonged to an island-hopping group of Homo heidelbergensis or Homo erectus. These ancient mariners would have crossed at least 40 miles of open sea. The sheer number of artifacts indicates that it was not just a one-time fluke, but required multiple crossings to establish a population. "We don't think it was just one guy hanging on a log," Strasser says, "but I doubt there was any sailing."
The findings, which will be published in the journal Hesperia this year, add to a growing but controversial view that modern humans and their precursors traveled by sea. So far, the oldest evidence of seafaring by modern humans has come from Australia, which was colonized about 60,000 years ago. Other, potentially earlier, cases have been more speculative.
Since the 1930s, archaeologists have noted similarities between tools on the Horn of Africa and the western Arabian Peninsula, suggesting that people crossed the Red Sea at the Bab al Mandab Strait, in addition to arriving through the Levant corridor. However, Amanuel Beyin of Stony Brook University in New York says the sea was just three miles across during glacial periods, and the geologic evidence does not rule out land bridges lasting one or two thousand years. Indeed, the Hamadryas baboon is found in both regions, and its arrival in the Arabian Peninsula occurred less than 200,000 years ago. "You can't argue the monkeys were using boats," he says.
Other hominid species may have been making port calls even earlier. Michael Morwood of the University of New England in Armidale, Australia, once suggested Homo erectus built boats to make the dangerous 15-mile crossing from Bali to the island of Flores in Indonesia, but he now believes the crossing was accidental, perhaps courtesy of a tsunami that would have swept a group of hominids off of one of the nearby islands and onto Flores approximately one million years ago.
On mainland Europe and the Middle East, the evidence of seafaring is more difficult to parse because hominids could just as easily have crossed overland or via temporary land bridges. Clive Finlayson of the Gibraltar Museum says he would be surprised if Neanderthals or other hominids never crossed the Mediterranean on purpose. "Movement through the Middle East must have been the main way of getting to Europe, but there must have been sporadic sea-crossings," he says.
The Rock of Gibraltar on the northern coast of the Mediterranean, Finlayson notes, is just nine miles from the Moroccan coastline. In fact, from the mouth of Gorham's Cave, a Neanderthal site in Gibraltar replete with stone tools, one can see clear across to the African quarry at Benzú, where people were making the same kinds of tools as late as 70,000 years ago. In Gibraltar, Finlayson and his colleagues have recently documented the 50,000-year-old bones of seals, dolphins, and even tuna with cut marks on them. They could have simply been beached animals, Finlayson admits. Even so, he says: "These people were not scared of water."