The Kalahari was formed several few million years ago when seismic shifts forced much of the land of Botswana upwards blocking the flow of the channel and creating a superlake that dried out over thousands of years leaving behind vast white salt deposits that form part of the desert as we know it today. Today the Okavango river remains as the Kalahari's only permanent river, however as in its history, it no longer flows into the sea, rather empties into a swamp area called the Okavango Delta. This region produces the Hoodia, a plant that is world renowned for suppressing hunger. It mainly eaten by the San people who live predominately in the north of the Kalahari and, after eating it, the San claim to go a further 24 hours without feeling any hunger, although there is no scientific evidence for any claims about Hoodia. There used to be over a million San living in the Kalahari desert, however that number is now down to about 2000 following years of persecution by neighbouring tribes.