An even more radical set of questions arises from the visions of some Western and Northern ayahuasqueros, particularly those steeped in evolutionary and ecological biology. Why do so many plants carry psychoactive tryptamines and other chemicals that are capable of producing profound consciousness-transforming perceptions in human beings, opening them up to the deepest mysteries of life and death? On one level this confirms the basic unity of all life on Earth, the oneness of the molecular genetic code. But the usual Darwinian assumption is that nothing evolves by chance -- natural selection works to favor those structures and capabilities that are adaptive in some way. So how is it adaptive for plants to produce alkaloids that seemingly serve no other particular function, and yet provide profound healing or insight in the human?