It seems like the Amazon is full of plants that act as medicine why is this so?

I’ll give it a shot.
We know humans have been evolving for 1 to 2 million years (pick your starting point), but only left Africa 100,000 to 200,000 years ago. Our early ancestors had much more time to evolve bodily functions optimized for that type of climate and surroundings.

There is an area in Western NY that still has primal forest. I’ll bet there are all kinds of good stuff growing there that benefited the Paleo-Indians.

Plants that have to survive in a very competitive environment (against insects and animals that want to eat them, against each other in competition for light and resources) develop various strategies, many of them chemical. That often results in unique compounds, some of which we learn to identify and exploit. And the Amazon has a tremendous diversity of plants, increasing the odds of finding something interesting.

Extremely diverse ecosystems lead to a diversity in molecules. So it’s not only that there’s so many plants, but that there’s so many plants (and animals) that are competing. This drives evolution and diversification. And as @syz mentions, this also drives competition, and many of our medicines are in fact toxic substances in the proper doses, so their weapons become our medicines. More competition, more evolution, more useful substances.

There’s also the fact that it is so dense, and thus not well explored by humans. There’s potentially thousands, if not hundreds of thousands, of species we have no knowledge of, any one of which may have something new that’s useful. Most of the inhabited landmasses have been well explored, and so the chances of finding anything new, while not nothing, are much lower than the chance of finding something amidst the teeming unknowns of the Amazon.

Perhaps we should work on not destroying it so much.

Your back yard is full of plants that can be very medicinal.

@Crazydawg Hit the nail on the head. Most plants, especially what we call weeds have incredible medicinal properties. As a matter of fact, most modern medicine and pharmaceuticals were derived from and copied from plant life.

Yup. I can see four medicinal plants, just off the top of my head, out my window right now here in Massachusetts: fiddlehead ferns (the wooly ones), self-heal, burdock, and balsam fir. And there’s probably a dozen or more I can’t identify yet in the same space.

@wildpotato Garlic, wild mint, dandelions, clover and lots lots more.

@Crazydawg This is fun. Same window, more medicinals: English ivy, false Solomon’s Seal, white birch, purple trillium. Hm, I may actually go grab some Seal for a poultice.

Jewel weed (rashes including poison ivy), St. John’s wort (depression), weeping willow (aspirin), witch hazel, black birch, oxalis, sorrel, and purslane all common around here (an hour or so west of @wildpotato.

@wildpotato Imdeed. Great adds!