Botswana documents tribal healers' knowledge

For generations, tribal healers all over the world have used knowledge of plants to treat medical problems. <br /><br />They might not have the science to explain why the plants work, but they have the experience. <br /><br />And the government in Botswana is trying to record all that is known before it vanishes for good. <br /><br />Al Jazeera's Peter Greste has been finding out more in Gaborone.