I go in hard, come out soft, and am never the same. What am I?

The object described by the riddle, which enters hard, emerges soft, and is forever altered, is chewing gum. When first unwrapped, a piece of chewing gum is typically firm and solid. As it is chewed, the warmth and mechanical action of the mouth transform its texture, making it soft, pliable, and elastic. This process also releases its initial flavor, which gradually diminishes until the gum becomes a tasteless, soft mass, never returning to its original state and usually discarded.

The practice of chewing gum is remarkably ancient, dating back to the Neolithic period. Archaeological findings include 9,000-year-old birch bark tar chewed by early humans, possibly for its antiseptic properties or as a glue for tools. Ancient Greeks famously chewed mastic gum, derived from the resin of the mastic tree, to clean their teeth and freshen breath. Meanwhile, indigenous peoples in the Americas, such as the Mayans and Aztecs, chewed chicle, a natural latex from the sapodilla tree, for similar purposes and to stave off hunger. North American Indians also chewed the sap from spruce trees.

The commercial chewing gum we recognize today began to take shape in the mid-19th century. Thomas Adams, an American inventor, was introduced to chicle by former Mexican President Antonio López de Santa Anna in the 1860s. Adams initially experimented with chicle as a rubber substitute but soon realized its potential as a chewing gum, launching "Adams New York Chewing Gum" in 1871. While chicle was the foundation (Review) for many early brands, modern chewing gum primarily uses synthetic gum bases, combined with various sweeteners, softeners, and flavorings to create the diverse range of products available today.