The use of animal skins to provide warmth or protect humans from the elements is thought to date back hundreds of thousands of years. In these very early days, animals from a kill would likely have been skinned so that the rawhide could be used as a primitive rain cover or maybe even a blanket. The timelines are hazy, but it was probably 8,000 to 4,000 BCE before humans discovered (either by chance or through trial and error) a way to extend the life of the rawhides through tanning, and in doing so produce the earliest forms of leather.
These earliest forms of tanning likely involved the use of salts, smoke, urine, and the pounding of animal fats or brains into the rawhide, but history widely credits the Greeks with inventing the first vegetable tanning process such that by 500 BCE vegetable tanned leather was a well-established trade in the region.
The word “tanning” comes from tannin: naturally occurring polyphenol (micronutrients) found in plants, seeds, bark, wood, leaves, and fruit skins which prevent the disintegration of the collagen fibers of the hide.
From Greece, the trade and know-how spread to Egypt and then to the Romans, where leather was used in armor, harnesses, and saddles, often with embellishments and decorations produced by punching or stamping the leather. Later, around the 8th century CE, the Moors of Spain further advanced the general tanning process to make the leather softer and by adding color to the leather. The Cordovan leather they produced from horse hides (so named after the city Cordova) was highly sought after throughout Europe.
While the use of leather continued to spread and vegetable tanning techniques were further improved upon and refined, it wasn’t until the 19th century that advancements in chemistry led to the next major evolution in leather production: chrome tanning.
Between 1840 and 1850 the use of chromium salts to speed up the tanning process was discovered, independently, by German technologist Friedrich Ludwig Knapp and Swedish Chemist Carl Erengisle Hyltén-Cavallius, shortening the tanning process down from months to days, and enabling the production of much softer leather for which wider applications could be found in the furniture, automotive, and apparel industry. This new process also brought down the cost of leather goods, making them more affordable. Today approximately 90% of the leather produced worldwide is chromium tanned.
Advancements in the latter half of the 20th century were more focussed on improving health and safety aspects and the environmental impact of the tanning process through, for example, the substitution of whale oils, the removal of carcinogenic products, and waste-water treatment.