Final answer:
Marijuana is the drug that is most characteristic of the "natural" era and is consumed close to its natural state unlike the significantly processed or synthesized drugs like cocaine, morphine, LSD, and methamphetamine.
Step-by-step explanation:
The drug that derives more or less entirely from a naturally-occurring substance and is characteristic of the "natural" era discussed in Chapter 1 is marijuana. Unlike substances like LSD, methamphetamine, and even refined cocaine and morphine, marijuana is consumed in a form that is very close to its natural state. Cocaine and morphine, despite being derived from natural sources (coca leaves and poppies, respectively), undergo significant processing to be used as drugs. LSD, while originally synthesized from a fungus, and methamphetamine are both primarily the products of chemical synthesis and cannot be considered natural in the context being discussed.