Did Columbus Bring Syphilis to Europe?

Famed explorer Christopher Columbus and his crew unleashed the scourge of syphilis on Europe, a new genetic study suggests, though some experts say the data is not conclusive.

The research adds more fuel to a controversial debate on the origins of the devastating sexually transmitted disease that can cause blindness, mental illness, and death.

Europe's first-known venereal syphilis epidemic occurred during the years immediately following Columbus's return, fueling a long-held theory that the explorer carried the disease to the continent.

Study lead author Kristin Harper and colleagues compared genetic data from 26 strains of the treponema bacteria family—those responsible for venereal syphilis as well as nonvenereal forms of the disease—and closely related ailments such as yaws, a tropical bacterial infection.

The results showed that modern-day syphilis strains resembled those found in South America.

This New World origin for syphilis strongly supports the Columbus theory, said Harper, an evolutionary biologist at Atlanta's Emory University.

"We hope to find genetic differences we can use to build a family tree of these bacteria," she added. "In doing that we hope to get an idea of where and when syphilis evolved."

Incomplete Tale

Bones on each side of the Atlantic have yielded some tantalizing but inconclusive clues suggesting where and when the disease existed before Columbus's voyages.

Numerous pre-Columbian Old World remains appear to show signs of syphilis, including pitted skulls and unnaturally fat lower leg bones, some researchers say.

But few examples survive, and those that appear to show syphilis may in fact be evidence of other related viruses.

"Diagnosis of specific [syphilis-causing] diseases can be problematic in skeletal remains from archaeological sites, because they are often fragmentary and poorly preserved," said Charlotte Roberts, a bioarchaeologist at Durham University in the United Kingdom.

"Without the complete skeleton—or in the case of treponemal disease diagnosis, the skull and long bones—a specific diagnosis cannot be made with ease."

While some argue that Old World bones "proving" the existence of pre-Columbian syphilis are suspect, Roberts claims the same can be said of New World remains suggesting an American origin.

Connie Mulligan, a molecular anthropologist at the University of Florida, disagrees with Harper's conclusions—saying that the existing genetic data does not begin to answer that question.

"Opportunistic timing and the fact that [the voyage and European syphilis outbreak] are so closely tied has provided this interesting historical question: Did he bring it back to the Old World, or was it already present in the Old World?" Mulligan asked.

"We just don't know."

She also notes that at least one theory suggests there is no genetic difference at all between syphilis and its relative ailments.

"Is it just the same disease that has different manifestations in different climates?" she asked.

"That's what I think Harper's data might be showing. ... To me that is very interesting, almost more interesting than the single geographic origin of venereal syphilis.

"In that case, asking where venereal syphilis evolved is the wrong question."

Harper's study was published recently in the journal PLoS Neglected Tropical Diseases.

Tandem Evolution

Geneticist Spencer Wells is a National Geographic Society Explorer-in-Residence and director of the society's Genographic Project. (The National Geographic Society owns National Geographic News.)

He said Harper's study "basically says we need to do a lot more work and look at a lot more of the genome, more DNA, and more strains of syphilis from around the world."

The syphilis mystery also spotlights how infectious diseases and humans have genetically evolved in tandem over time, he added.

Yaws, which many scientists believe descended from syphilis, has likely been with humans since their origins in Africa.

"We probably carried it around the world with us," Wells said. "Over hundreds of thousands or even millions of years, you slowly start to adjust to each other so that the organism still causes a disease, but it doesn't cause a very bad disease."

"But something happened at some [recent] point that likely allowed it to develop into syphilis, and it took off as a new kind of disease that caused all kinds of problems."

Wells notes that the genetic study of such diseases can teach us a great deal about the way our own genes have evolved.

"We see clear evidence in our own genome of adaptations to disease," he said. "Recently people have started looking at the genomes of infectious diseases, and we tend to see overlap in those processes [of adaptation]."

The use of genetics to track the origins and movements of disease is a rapidly growing field.

But even Harper suggests that we may never be able to definitively identify the mysterious origins of syphilis and Columbus's possible role in its spread.

"The truth is I think we're never going to nail this thing—we just don't have the strains to do that," she said.

"We have to work with what we have, and we have an [incomplete] picture that we have to make the most of."

by news.nationalgeographic.com

Read More..

Parasite Makes Ants Resemble Berries

Scientists have discovered a parasite in the tropical forests of Central and South America that makes its ant hosts look like juicy, red berries ripe for the picking.Presumably the change in appearance tricks foraging birds into eating the otherwise unappetizing ants—parasites and all. The parasites travel through the birds' guts intact and are pooped out, which allows them to spread.

"These ants, in nature, go out and collect bird feces," explained Steve Yanoviak, an insect ecologist at the University of Arkansas in Little Rock.

The finding is the first known example of fruit mimicry caused by a parasite, he and his colleagues conclude in their study, which has been accepted for publication in the journal The American Naturalist.
Red Rears

Yanoviak's colleague Robert Dudley, a professor of integrative biology at the University of California, Berkeley, happened upon the infected tree-dwelling ants in Panama while studying their ability to glide.

Cephalotes atratus ants can make midair maneuvers, so that if knocked off a branch, they can steer toward the tree trunk, grab hold, and climb back up, the team showed in earlier work.

Dudley also noticed that some ants' gasters—the rear segments of their abdomens—were bright red. Yanoviak sliced open such a gaster in the lab and found it was full of the eggs of a parasitic nematode, or roundworm.

The researchers suspect the nematodes grow up inside the ants, then cause the hard outer layer of the gasters to thin. When combined with the yellowish coloring of worm eggs, this makes the body segments appear amber. "When you combine those two effects in the sunlight, you get a nice, bright red ant rear end.

Infected ants tend to hold their infested gasters in an elevated position over the rest of their bodies, making them "really conspicuous," he added.

The ants also become sluggish, and the gaster itself weakens, making it easily plucked off by birds, the researchers noted.

"[The ants] often feed out on leaf surfaces collecting pollen, collecting bird droppings, so they are pretty highly exposed," Yanoviak said.

Tricked Birds?

Yanoviak and his colleagues hypothesize that birds are tricked into thinking infected ants are ripe berries and eating them. Birds don't normally feast on Cephalotes atratus ants, which are thickly armored and full of bad-tasting chemicals.

The eggs pass unharmed through the birds' digestive systems. Ants then eat the bird feces, giving rise to a new generation of parasites in a new population of ants.

However, the researchers have not yet observed a bird actually eat one of the ants.

To test the hypothesis in the lab, Yanoviak fed an infected ant to a chicken. The parasite eggs came out in the chicken feces unscathed, he noted.

He also examined pieces of bird droppings collected from ants marching back to their colonies and found a parasite similar to the one that turns the ant gasters red.

"No matter how we look at it, somehow that parasite has to infect new colonies, or else it would die with its host colony. So there has to be a mechanism for transport to a new colony," Yanoviak said.

"And the association of this ant species in particular with bird droppings makes the message even stronger for implicating the bird as the vector."

Janice Moore is a biologist at Colorado State University in Fort Collins and an expert on the ecology and evolution of parasitic worms.

She said the researchers have done just about everything they could to show the infected ants might be fruit mimics and how the parasite could spread among ant colonies.

"That's pretty cool," she said.

Humans notice the fruit mimic ants readily because they are readily visible, she added, but other examples of parasite-induced change probably abound.

"As humans, we are highly visual and we notice visual modifications," she wrote in a follow-up email. "We are less conscious of, say, olfactory or auditory alterations.

"We know of a few such cases," she said, "but they are thin on the ground—probably because we don't notice them."

by news.nationalgeographic.com

Read More..

Ancient Pandas Competed With Giant Apes for Bamboo

New fossils suggest ancient pandas competed with the largest known apes for habitat and food nearly half a million years ago on the tropical coast of southern China, scientists say.

The 400,000-year-old fossils of a giant panda were uncovered alongside the remains of a titan-sized, ancient ape called Gigantopithecus blacki, said Huang Wanbo, a paleontologist at Beijing's Institute of Vertebrate Paleontology and Paleoanthropology.

Excavated from a limestone cave on the island province of Hainan, the fossils suggest that both the giant pandas and the Giganto apes survived on a mostly bamboo diet, said Huang.

Hainan island was a bamboo-covered, hilly peninsula 400,000 years ago, Huang said. Today it is an island separated from the Chinese mainland by a 15-mile-wide (25-kilometer-wide) strait.

Three-Way Competition

Russell Ciochon, a professor at the University of Iowa who has joined several fossil digs in China but was not involved in the Hainan excavation, said the findings expand the known geographic range of nine- to ten-foot (three-meter) Giganto, which he called "the largest ape that ever existed."

The Giganto ape became extinct about 300,000 years ago, after about a half-million years of overlap with early humans, according to Ciochon.

Huang said he believes the ape lost out in a three-way struggle with giant pandas and early humans over food and habitat.

Ancient panda fossils have been found before near Giganto ape remnants, and early human fossils in China have been found in the vicinity of ancient pandas.

If early humans—armed with primitive weapons like stone axes and fire—migrated like the panda through what is now southern China, they likely had contact with the giant apes, Huang said.

Fossils of this early human species—a hunter-gatherer known as Peking Man or Homo erectus—have been uncovered around Beijing in northern China, about 1,200 miles (2,000 kilometers) north of Hainan.

Ciochon said he once agreed that the Giganto ape was the first loser in a survival competition with pandas and primitive humans, but today he is not so sure.

"The panda and the Giganto were living side by side in these subtropical forests, and probably competing for food resources," he said, "but Homo erectus was likely to be living in other habitats."

No Homo erectus fossils have been found in what is now southern China, but the area has not been thoroughly studied by paleontologists.

Panda Struggles

Huang said that the Hainan panda fossil provided a new piece in the puzzle of the panda's eight-million-year-long evolution from a meat-eater into a reclusive bamboo-eater.

The earliest pandas were fierce carnivores, scientists say. While technically classified as omnivores, today's pandas primarily depend on bamboo, which they spend an average of 12 hours a day eating.

The new fossils suggest the panda of 400,000 years ago, which was slightly larger than the modern giant panda, had by that time already become completely dependent on bamboo for survival, Huang said.

Huang said pandas were traditionally hunted for their pelts, and this may have been the case as far back as several hundred thousand years ago.

According to Huang, "400,000 years ago, there were many more pandas than humans here."

The human population in China has since grown to more than 1.3 billion, while the number of pandas has dwindled to about 1,600, according to Chinese conservationists.

Alarmed by a government inspection that turned up only 1,100 giant pandas in the late 1980s, China began at that time working with a global coalition of conservationists to save the species.

Fan Zhiyong, species program director for the conservation nonprofit WWF China, said the giant panda population has been decimated by large-scale human activities including "road and dam construction, mining, tourism, logging, and poaching."

Making panda poaching a capital crime, setting up a patchwork of panda nature reserves in the Himalayan foothills of western China, and creating a captive breeding program have all helped forestall the panda's extinction, conservationists say.

Paleontologist Huang, meanwhile, has proposed creating a panda DNA database that could help map the evolutionary history of the giant panda. He said that unlocking the secrets of the panda's genetic past might one day provide the key to protecting its future.

by news.nationalgeographic.com

Read More..