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| Hominids Went Out of Africa on Rafts Posted: 08 Jan 2010 02:59 PM PST
ANAHEIM, Calif. — Human ancestors that left Africa hundreds of thousands of years ago to see the rest of the world were no landlubbers. Stone hand axes unearthed on the Mediterranean island of Crete indicate that an ancient Homo species — perhaps Homo erectus — had used rafts or other seagoing vessels to cross from northern Africa to Europe via at least some of the larger islands in between, says archaeologist Thomas Strasser of Providence College in Rhode Island.
Until now, the oldest known human settlements on Crete dated to around 9,000 years ago. Traditional theories hold that early farming groups in southern Europe and the Middle East first navigated vessels to Crete and other Mediterranean islands at that time. "We're just going to have to accept that, as soon as hominids left Africa, they were long-distance seafarers and rapidly spread all over the place," Strasser says. Other researchers have controversially suggested that H. erectus navigated rafts across short stretches of sea in Indonesia around 800,000 years ago and that Neandertals crossed the Strait of Gibraltar perhaps 60,000 years ago.
Questions remain about whether African hominids used Crete as a stepping stone to reach Europe or, in a Stone Age Gilligan's Island scenario, accidentally ended up on Crete from time to time when close-to-shore rafts were blown out to sea, remarks archaeologist Robert Tykot of the University of South Florida in Tampa. Only in the past decade have researchers established that people reached Crete before 6,000 years ago, Tykot says. Strasser's team cannot yet say precisely when or for what reason hominids traveled to Crete. Large sets of hand axes found on the island suggest a fairly substantial population size, downplaying the possibility of a Gilligan Island's scenario, in Strasser's view. In excavations conducted near Crete's southwestern coast during 2008 and 2009, Strasser's team unearthed hand axes at caves and rock shelters. Most of these sites were situated in an area called Preveli Gorge, where a river has gouged through many layers of rocky sediment. At Preveli Gorge, Stone Age artifacts were excavated from four terraces along a rocky outcrop that overlooks the Mediterranean Sea. Tectonic activity has pushed older sediment above younger sediment on Crete, so 130,000-year-old artifacts emerged from the uppermost terrace. Other terraces received age estimates of 110,000 years, 80,000 years and 45,000 years. These minimum age estimates relied on comparisons of artifact-bearing sediment to sediment from sea cores with known ages. Geologists are now assessing whether absolute dating techniques can be applied to Crete's Stone Age sites, Strasser says. Intriguingly, he notes, hand axes found on Crete were made from local quartz but display a style typical of ancient African artifacts. "Hominids adapted to whatever material was available on the island for tool making," Strasser proposes. "There could be tools made from different types of stone in other parts of Crete." Strasser has conducted excavations on Crete for the past 20 years. He had been searching for relatively small implements that would have been made from chunks of chert no more than 11,000 years ago. But a current team member, archaeologist Curtis Runnels of Boston University, pointed out that Stone Age folk would likely have favored quartz for their larger implements. "Once we started looking for quartz tools, everything changed," Strasser says. Image: NASA See Also: |
| Bee Colony Collapse May Have Several Causes Posted: 08 Jan 2010 09:39 AM PST
When suspiciously large numbers of honeybee colonies started collapsing in late 2006, the search began to find the culprit behind the mysterious deaths. Now it seems a whole web of problems may becausing what's known as colony collapse disorder. It's becoming clear that there is no single parasite, virus or chemical to blame, argues Frances Ratnieks, a bee scientist at University of Sussex in Brighton. Instead, honeybees are probably dying for all kinds of different reasons from loss of their foraging grounds to increased exposure to global pathogens, Ratnieks wrote in a review of the issue in the journal Science. "We may conclude that colonies are dying for different reasons in different parts of the world and I would say that if that is the case, I would not be the least bit surprised," Ratnieks told Wired.com. A variety of pests, viruses and parasites could all be working together to stress the bees. And in some ways, that's worse than trying to take on a single culprit: The problems with beekeeping are systemic, Ratnieks said, and can't be solved with a new pesticide or technique.
In an increasingly globalized world, bee pathogens travel quickly between bee populations. Over the last decades, the Varroa destructor mite has spread from Asian honeybees to the rest of the continents. The gut parasite Nosema ceranae has taken the same path. Both species are believed to make existing bee diseases worse. V. destructor took about four decades, reaching North America about a decade ago. N. ceranae circled the globe in a quarter of that time. "It is certainly a case in the modern world, pathogens can be transmitted from one corner of the world to an another quickly," Ratnieks said. He compared the bee pathogen problems to those humans are encountering with swine flu and other emerging diseases, which can spread quickly thanks to modern transportation. "Even though the U.S. is a big country, what shows up in one part of the country shows up in the other parts of the county in no-time flat," he said. That's in part because of the economics of beekeeping. The $2 billion almond crop in California requires 1,000,000 honeybee hives for cross-pollination. That's more than 40 percent of all the beehives in the country. So, come almond-tree flowering season, which begins in February, apiarists load up their hives on flatbeds and truck them to San Joaquin Valley. While this pilgrimage may be necessary to keep churning out cheap almonds, it also createsa melting pot of pathogens.And the moving and trucking itselfcould negatively impact the bees, too. Ratnieks also suspects that honeybees are more susceptible to disease because their natural forage — weeds and gardens, etc. — has been wiped out by single-crop farming in the major farming valleys of the country. Add it all up and the honeybees are fighting the battle to survive on several, interconnected fronts. "It's harder to keep a hive alive now. It used to be with bees in America, if the hive was alive and thriving, chances are the hive would be alive and thriving the next year," said Ratnieks. "Now, they are feeding their hives with supplements and feeding them with chemicals, they are having to peddle quite hard just to keep their hives alive." Last year, there were enough honeybees to keep the almond trees pollinated, but last summer's weather conditions were bad in North Dakota and the neighboring states where the California hives often spend the season. With the big almond flowering coming up, and the bees in bad condition, the beginning of next month could harbor a nasty surprise for nut farmers. "In early February, that's when the rubber hits the road or the shit hits the fan," Ratnieks concluded. Citation: "Clarity on Honey Bee Collapse?" by Francis L. W. Ratnieks and Norman L. Carreck in Science, 8 JANUARY 2010 VOL 327. Image: BBCworldservice/Flickr
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