In a cluttered ground-floor laboratory at one corner of the University of Washington’s Seattle campus, Sam Wasser hunches over a gray toaster-size instrument. “This is it,” he says. “This is what makes it all possible.” The device is a liquid-nitrogen-cooled mill that can pulverize a piece of tusk without destroying its DNA. Genetic detectives can then use that information to determine where in the vast continent of Africa the elephant lived and died. Over the next few months, Wasser and his team hope to unravel the origins of the largest load of contraband ivory ever seized and furnish international investigators with the data they need to crack the criminal networks that continue to devastate Africa’s elephant herds.
Tusks grow throughout an elephant’s life and can weigh up to 130 pounds. One study noted that the average weight of a traded tusk dropped from 22 pounds in 1979 to 7 pounds in 1990.
Such knowledge is essential if African countries and their supporters hope to enforce the ban on international ivory trading enacted 16 years ago. The agreement was reached to stem the slaughter of the herds, whose numbers had dropped from 1.3 million in 1979 to just over 600,000 in 1989. For a few years, poaching declined, herds began recovering, and in 1997 USA Today proclaimed that “the illegal ivory trade has been virtually wiped out.”
The declaration proved premature. Smugglers became more sophisticated and poachers more covert. Elephant kills on the savanna are easy to spot and count. But as logging opened up vast swaths of Central African rain forest, poachers increasingly targeted elusive forest elephants under a green canopy that hid their kills from aerial surveillance.
The African elephant population is estimated to be about 500,000, but experts fear that the killing in some
As poachers kill off males with the largest tusks, elephants with shorter tusks—younger males and females—become more frequent targets. regions may even exceed the slaughter of the late 1970s. “There are vast areas in Central Africa where the habitat is intact but empty,” says Richard Ruggiero, the U.S. Fish and Wildlife Service’s program officer for African elephant conservation. “There are no animals left.”
In June 2002 Singapore customs agents seized the largest haul of contraband ivory ever: 6 1/2 tons, including 535 tusks and 42,000 ivory cylinders used to make hanko, prestigious signature stamps that can fetch hundreds of dollars each. Investigators discovered that the ivory had been sent from Zambia—which has tried and failed to obtain special permission to sell stockpiled ivory—through Malawi and on to South Africa, a country that later won approval for a onetime sale. The cargo was then shipped to Singapore and was on its way to Yokohama. Investigators suspect that at least some of the booty came from the chaotic, poacher-plagued Democratic Republic of the Congo, but they need definitive clues about its origins.
“If that seizure came from 25 different places, that would tell us the smuggling network is quite sophisticated,” says Bill Clark, an enforcement officer at the Nature and Parks Authority in Israel who is assigned to Interpol’s wildlife-smuggling investigation. “If it came from only two or three, the population there is getting hit very heavily, but the network is not so extensive.” Tracing the origins of smuggled ivory, he says, would help investigators determine “the magnitude of the trade, the structure of the criminal syndicates running it, and the dynamics of the smuggling operations.”
Clark knew of Wasser’s research on elephant genetics, so last August, after completing the necessary formalities, he sent samples from the Singapore seizure to Seattle.
Ever since the ivory-trading ban took effect, scientists have labored to decipher the tales tusks might tell. First to try was a South African team led by Nikolaas van der Merwe, a professor of natural history at the University of Cape Town. South Africa has a special interest in solving the puzzle. In the 1990s, South Africa and four other southern African countries had repeatedly sought and occasionally won permission to sell ivory from their better-protected and sometimes overpopulated herds. But Kenya and other nations complained that legal sales would give cover to contraband shipments because officials had no way of knowing where the ivory actually came from—where, for example, a tiny nation like Burundi, with no elephants of its own, got the thousands of tusks it exported in the 1980s.
The South Africans wanted a “fingerprint” that would distinguish their ivory. They began by looking at isotopes of several elements in ivory. The difference between using DNA analysis and isotope tracking is a variation on the nature versus nurture debate: DNA records an organism’s genetic inheritance, and isotopes reflect the composition of the environment in which it grows. Trees and shrubs are rich in carbon-12, and tropical grasses are rich in carbon-13. The proportions of the isotopes in ivory reflect the diets of the elephants. Nitrogen isotopes vary with rainfall, reflecting the climate elephants inhabit. And the radioactive isotope strontium-87, which scientists use to date rocks, varies with the age of rock in soil.
By overlaying isotope ratios of these three elements, the South Africans were able to distinguish ivory not only from different regions and countries but also from parks as few as 150 miles apart. They proposed an isotope map of Africa.
But the map kept changing. In 1995 U.S. researchers found that carbon isotope ratios in elephants at Amboseli National Park in Kenya had shifted over decades, reflecting changes in the elephants’ diet as they crowded into the park to escape poaching, ate up the park’s trees, and switched to grass. Nitrogen ratios proved a “blunt” measure, says paleontologist Paul Koch of the University of California at Santa Cruz. He and his colleagues got different carbon and nitrogen readings at different points along a single molar. As the tooth grew, it recorded a diary of changing environment and diet.
Other researchers began looking to DNA. Prompted by the Wildlife Conservation Society, a young Kenyan-born biologist named Nick Georgiadis embarked on what he called “a long and wonderful hike” across 10 African countries, taking biopsy-dart samples from 600 elephants. He and his colleagues extracted mitochondrial DNA from the samples and screened it for specific markers, using a technique called restriction mapping. The results appeared to detect different markers in elephants from different regions—a first step toward a continent-wide genotype map. But a second look was deflating. Elephants were just too mobile; too much gene flow had occurred, especially between East and South African elephants, to preserve distinctive genetic signatures.
Georgiadis’s work did, however, prove valuable. Taxonomists and field biologists had long wondered just how different Africa’s two designated elephant subspecies—the familiar, widespread savanna elephants and the elusive forest elephants—actually were. With their round ears, sloping brows, and straight, downward-pointing tusks, the forest elephants certainly look different. Georgiadis concluded that the two lines diverged several million years ago, but he needed more evidence. He arranged for further analysis at the National Cancer Institute’s Laboratory of Genomic Diversity. There, with help from Wasser and his colleagues in Seattle, geneticist Al Roca sequenced introns—vestigial sections of DNA from the nucleus that accumulate mutations quickly because they don’t code for any physical traits—and confirmed that forest and savanna elephants diverged at least 2.6 million and probably more than 3 million years ago—long enough to render them separate species.
