Now, drug companies are tapping into the San's knowledge, and betting millions that these bushmen can help the most advanced societies on earth.

All because of the hoodia plant, which the San people have long relied on to survive.

One San hunter says "I learned it from my forefathers. It is my food, my water, my medicine."

It's medicine because a little hoodia can kill severe hunger pains and quench the most powerful thirst. For the desert hunter it is a godsend.

Now one man's cure for hunger is turning into another's diet drug.

Phizer, the pharmaceutical giant, has invested $21 million dollars to turn hoodia into an appetite suppressant. With 100 million westerners dangerously overweight or obese, the market for diet drugs is billions of dollars a year. But the San, say the people who study them, were mystified when told the outside world had a weight problem.

Nigel Crawhall from the South African San Institute says "Why would anyone want to lose weight by taking the hoodia plant, because it's meant for traveling across the desert? So people thought it was a bit weird in the first place."

The drug's developers call the active compound in the plant P57. They say it works by mimicking the effect glucose has on the nerve cells in the brain, in effect telling us we're full, even when we are not... thus curbing the appetite.

P57 is still a few years from reaching the market, and there has already been a legal battle over it. The first company to patent P57 tried to do it without paying the bushmen any money. One court challenge later, the San had an agreement: they now help cultivate the plant, and should the drug come to market, their impoverished community stands to prosper.

"At first we were angry," says one San leader. "Others would get rich and we would stay poor. Now we pray the product will succeed, and we will all benefit."