Why is it that chemicals forom the other side....?

Question

Why is it that chemicals forom the other side of the earth, like chocollate or coffee, or tobbacco, would have effects on humans, whom have never ever seen it before? Why are these receptors in our brain Naturally there?

Answer 1

There are several types of receptors that are vulnerable to being affected.  Plants have been in an evolutionary arms race to produce toxins to attack various receptors and enzymes of the animals that eat them.  We share the basic physiology with other animals so it is only natural we would be susceptible to many of the toxins.  The tropics tend to have more varieties of plants with toxins since the plant has leaves the whole year.  In the north, animals can't really  feed mainly on deciduous leaves because the animal wouldn't have anything to eat for half the year.  That probably reduces the need to produce toxins to discourage plant eaters.