The blood samples went to Stephen O'Brien at NIH. He had studied the domestic cat as a model for human viral cancers and was interested in genetic variation. In most cat species, enzymes in the blood differ genetically between individuals by 20 percent to 50 percent. But the cheetahs' blood enzymes were all alike. "We found nothing," says O'Brien, no variation at all. After looking at 52 genes, O'Brien halted the study. The cheetahs were virtual clones.
Were they catastrophically inbred? To test that hypothesis, O'Brien and Wildt needed more samples. Zookeepers had made great strides in breeding cheetahs since the three cubs died in Philadelphia, but Wildlife Safari—with Marker in charge of the cheetahs—had the most successful breeding operation in the country, with three dozen animals on hand. It would successfully raise more than 100 cheetah cubs during the 16 years Marker worked there.
In Oregon, Wildt and O'Brien took skin samples from eight Wildlife Safari cheetahs and grafted them onto other cheetahs. Ordinarily, as in human transplants, a host will reject a donor organ unless there is a close tissue match and an assist from immunosuppressant drugs. But the cheetah grafts were accepted in every case. This was disturbing news, for it meant that their immune systems were so similar that almost every cheetah in the world had the same vulnerability to the same diseases. In fact, in 1982, Wildlife Safari lost 60 percent of its cheetahs to an epidemic of viral peritonitis. "It went through the center like wildfire," Marker says. The same disease in any genetically diverse cat population could be expected to kill 2 percent to 5 percent of its victims.
Where had the cheetah gone wrong? By analyzing the few variations in cheetah DNA, O'Brien and Wildt determined that cheetahs had passed through a population "bottleneck" about 12,000 years ago. Some apocalyptic event had wiped out all but a few animals that then interbred, with disastrous consequences for the animal's gene pool. The obvious culprit was the onset of the last ice age, a cold snap that coincided with the extinction of saber-toothed cats, mastodons and other large prehistoric mammals. Fossil evidence shows that cheetahs evolved in North America about 8.5 million years ago and then spread throughout Asia, India, Europe and Africa; the modern species appeared about 200,000 years ago. The bottleneck wiped out all of North America's animals.
Wildt, O'Brien and Marker's National Zoo-led studies have informed everything that has happened in cheetah management and conservation since the 1980s. Researchers now know that the cheetah will not be a robust, vigorous species anytime in the foreseeable future and that saving the animals, Marker's proclaimed goal, thus requires a combination of strategies. Protecting and studying them in the wild is one approach, while at the same time scientists are refining techniques to breed them in captivity, hoping to build what Wildt calls an insurance policy for the wild population. The work continues today at the new Cheetah Science Facility in Front Royal, Virginia.
Marker, by then divorced, moved to Washington in 1988 to run the National Zoo's program to broaden genetic analysis in breeding cheetahs and other animals. She spent three years there before shedding her worldly goods and moving to Namibia. She sold what she could—including her mobile home in Oregon—gave away most of the rest and departed with $15,000.
"I thought if I told enough people about the threat to cheetahs, they would take care of it, but they never did," Marker says. "[People] were always saying, ‘somebody ought to do something about cheetahs,' but I could never find out who ‘somebody' was. So I went."
Marker arrived in namibia at a watershed moment. Colonized by Germany in the 19th century and annexed by apartheid South Africa after World War I, the country known as South West Africa became an international cause in the 1960s as the guerrilla South West Africa People's Organization (SWAPO) fought to end colonialism. In 1988, South Africa agreed to vacate Namibia, and the country gained independence in March 1990. Marker arrived April 1, 1991. "At first there was a lot of standoffishness, especially among the white folks," she recalls. "I was a U.S. citizen, and we had supported SWAPO, which, as far as they were concerned, was the wrong side."
With two million people living in an area nearly twice the size of California, Namibia is one of the least populated countries on earth; a motorist can drive 100 miles without seeing more than a half-dozen people. And the countryside teems with wildlife. Troops of jeering baboons greet motorists along the highway leading north from Windhoek, the capital. Families of wart hogs snuffle through the underbrush, and bushy-tailed jackals lurk in the grass. At water holes even a casual visitor can be confident of seeing a suite of marvelous creatures—eland, kudu, oryx, hartebeest. In all, Namibia boasts more than 20 species of antelope.
The cheetah is a top-of-the-line predator on the high plains. But, as Marker notes, cheetahs are one-trick cats. They can run down and kill anything their own size, or considerably bigger if they hunt together, but their legendary burst of speed—up to 70 miles per hour—is good for only about a quarter of a mile, and the chase leaves them badly winded and vulnerable. Bigger, nastier opportunists—lions, leopards and hyenas—frequently steal cheetah kills and, for good measure, then kill the exhausted cheetah's young.