The relatively short history of humans on the planet Earth has been, until recently, one of constant battles for survival against great odds.
According to the Toba catastrophe theory, around 70,000 years ago when the Toba supervolcano in Indonesia erupted, human beings were reduced in number to around 3000-10,000. The 1000-year volcanic winter which resulted from the eruption caused this severe reduction in human population.
This was a population bottleneck which could have caused the extinction of the species.
However some hardy humans on the coast of South Africa are said to have survived by eating corms and seafood. There was not much else growing on land and there were few animals for hunting. These humans somehow made it through this ice age to later migrate all over the world and result in where we are today.