The discovery that the brain contains specific receptors for manufactured opiate drugs such as morphine implies that the body must make an ___ substance that interacts with those same receptors.

ENDOGENOUS

Explanation: Receptors readily binds with biochemical messangers (called ligand) in the body system.

A particular receptor will only bind with a specific ligand, which translates that a specific receptors which readily binds with opiate drugs (such as morphine and oxycodone) for reducing body response to pain, must have been in the past, had an interaction with an endogenous biomolecule similar in molecular composition with that of opioid pain relievers .

if you know your abc's you should be able to get your answer or just use google

some scientists like gregory adcock agree with thorne's theory of regional continuity.

others, like chris stringer and ian tattersall, believe thorne's results may be contaminated or misinterpreted.