Clay lick

Geophagia (/dʒiəˈfeɪdʒəˌ-dʒiə/; also known as geophagy /dʒiˈɒfədʒi/) is the practice of eating earth or soil-like substrates such as clay or chalk. It occurs in non-human animals where it may be a normal or abnormal behaviour, and also in humans, most often in rural or preindustrial societies among children and pregnant women. Human geophagia may be related to pica, an eating disorder in the Diagnostic and Statistical Manual of Mental Disorders (DSM) characterized by abnormal cravings for non-nutritive items.

Some researchers believe that humans first ate soil in Africa:

The oldest evidence of geophagia practised by humans comes from the prehistoric site at Kalambo Falls on the border between Zambia and Tanzania (Root-Bernstein & Root-Bernstein, 2000). Here, a calcium-rich white clay was found alongside the bones of Homo habilis (the immediate predecessor of Homo sapiens).

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Wikipedia