At the end of the esophagus is a thick ring of a muscle called a sphincter which allows food to enter the stomach but not from the stomach back into the esophagus. Once the food enters the stomach it is mixed with the digestive juices.
Lamarck was one of the first scientists to propose that species evolve by natural selection. Lyell was one of the first to say that Earth must be far older than most people believed. Lamarck's inheritance of acquired characteristics is has become a widely accepted scientific theory.