The plant we commonly refer to as 'Cannabis', or 'Hemp' has been used by us, our species, for at least 10'000 years. Early explorers and botanists placed its origins in and around Central Asia; like the Hindu Kush-mountain area and North Afghanistan.

Go back even farther in time, to when primitive creatures were living their lives, just waiting to evolve into us. Remember that they would have eaten plants more than they hunted because hunting was dangerous. Most of the animals worth hunting back then would have been vicious compared to the cows and sheep we have now. Eating plants and herbs was far easier than risking their lives.
Imagine smelling a huge and bushy Cannabis plant in full bloom. A sweet and delicious smell to something that's, probably hungry most of the time...

Once the buds and flowers of the plant have been eaten, the digestive process absorbs many chemicals that are contained in within them. Those chemicals reach the brain and the Central Nervous System, and that union causes an effect deep within the brain, altering the perceptions of the creature that ate the buds and flowers of the cannabis plant.

These primitive creatures munched away on many plants and herbs, but they continued to eat the buds and flowers of this cannabis plant right up to and, past the birth of our species, Homo Sapiens-Sapiens, and that adds up to Millions of years. How can we be sure? Deep within the Central Nervous System there are specific parts, called RECEPTORS that ONLY cling to certain chemicals. The Central Nervous System is thought of as being only possessed by LIVING creatures; creatures that evolve. The evolved state that we have reached can be, at least in part if not in whole, attributed to the development of the Central Nervous System.
The chemicals found in the Cannabis plant, the ones that cause a psychoactive effect (CBN,CBD,Delta9-THC), have special receptors specifically for them, in our brain. This could not be possible without the continued ingestion of those chemicals; physical proof that psychoactive chemicals are a part of our evolution; they opened the minds of the primitive creatures that ate from the plants and mushrooms which allowed the birth of us, man-kind.