Primordial soup

Primordial soup was a liquid substance composed largely of sugars and amino acids. The Seventh Doctor referred to it as "the most precious substance in the universe, from which all life springs." (TV: Ghost Light)

Circa 400 million BC, the Fourth Doctor, Romana and Duggan discovered a pool of primordial soup (which the Doctor referred to as "amniotic fluid") in the middle of what would one day be the Atlantic Ocean. Nearby, Scaroth tried to take off in his ship, but it exploded, releasing radiation which reacted with the soup. As the Doctor had earlier explained, the amino acids would fuse to form cells which would eventually evolve into plants and animals. (TV: City of Death)

In 1883, Light devolved Inspector Mackenzie into primordial soup (as evidenced by the sight of Mackenzie's medallion dangling from the ladle), and served a tureen of it to Josiah Samuel Smith and his dinner guests, though none of them ate it. (TV: Ghost Light)