Whenever modern humans inhabited environments containing plants with psychoactive properties, they had the cognitive capacity to discover and use those properties.

The areca palm is native to Southeast Asia; the coca plant is native to South America; the tobacco plant is native to the Americas; cannabis is native to Central Asia; the opium poppy appears to have originated in the western Mediterranean.

Each of these plants was available to the modern humans who inhabited its range throughout human prehistory.

The probability that modern humans, with their cognitive sophistication, lived alongside these plants for tens of thousands of years without discovering their properties seems low.

But the probability that the discoveries left no archaeological trace for most of those tens of thousands of years — and that the traces we can detect begin only with the specific conditions and techniques that modern archaeochemistry can identify — seems high.