A United Nations (U.N.) human rights expert said that Botswana's government should have negotiated with an ancient tribe of hunter-gatherers before moving to force them from a Kalahari game reserve...The San [Bushmen] say they are being pushed out of the Central Kalahari Game Reserve in preparation for government-sponsored diamond mining, a claim denied by Debswana, the partly state-owned company that controls Botswana's mines...Their case has been taken up by tribal advocacy group Survival International, which has been a vocal critic of international diamond giant De Beers, the company that shares control of Debswana with the Botswana government.