A recent research study has shown that occupation of caves by early hominins in South Africa is restricted to dry phases. The full article can be accessed through Nature via this link, https://www.nature.com/articles/s41586-018-0711-0 or you can read more in the Conversation piece here:
https://theconversation.com/how-we-calculated-the-age-of-caves-in-the-cradle-of-humankind-and-why-it-matters-104856