Humans constantly alter the world. We fire fields, turn forests into farms and breed plants and animals. But humans do not just reshape our...

Humans constantly alter the world. We fire fields, turn forests into farms and breed plants and animals. But humans do not just reshape our external world – we engineer our internal worlds and reshape our minds.
One way we do this is by upgrading our mental “software”, so to speak, with myths, religion, philosophy and psychology. The other is to change our mental hardware – our brains. And we do that with chemistry.
Today, humans use thousands of psychoactive compounds to alter our experience of the world. Many derive from plants and fungi, others we manufacture. Some, like coffee and tea, increase alertness – others, like alcohol and opiates, decrease it. Psychiatric drugs affect mood, while psychedelics alter reality.
We alter brain chemistry for all kinds of reasons, using substances recreationally, socially, medicinally and ritually. Wild animals sometimes eat fermented fruit, but there is little evidence that they eat psychoactive plants. We are unusual animals in our enthusiasm for getting drunk and high. But when, where and why did it all start?
Pleistocene period
Given humanity’s love of drugs and alcohol, you might assume getting high is an ancient, even prehistoric tradition. Some researchers have suggested prehistoric cave paintings were made by humans experiencing altered states of consciousness.
Others, perhaps inspired more by...