Historically, a human being was not necessarily a natural person in some jurisdictions where a slave was a thing (subject of a property right) rather than a person. In many cases, fundamental human rights are implicitly granted only to natural persons.
Phenylalanine amino acid > Tyrosine amino acid > L-Dopa > Dopamine > Norepinephrine > Epinephrine. Mucuna pruriens is an herb that contains a small percentage of natural L Dopa. Mucuna pruriens is available without a prescription. For more information on mucuna pruriens and levodopa, click on the link provided.
1 Examples of foods high in tryptophan include: cheese, chicken, soy products, eggs, tofu, fish, milk, turkey, nuts, peanuts and peanut butter, pumpkin seeds, and sesame seeds.  To make tryptophan-laden meals more effective, make them high in complex carbohydrates.