As the name implies, pond scum grows on the surface of ponds and other bodies of fresh water. The ideal environment for pond scum is relatively warm still water with plenty of nutrients, and stagnant water is almost always expected to be covered with a film of pond scum.
Pond scum is often considered a weed or pest, and various measures are taken to mitigate its growth. Overgrowth of pond scum can make a body of water unfit for use, both because of the physical mass and - particularly in the case of cyanobacteria - by making the water toxic. In drought prone areas waterways can flow slowly or not at all as water levels drop, allowing pond scum to grow uncontrollably and render the remaining water supplies unfit for use or consumption. This is made worse by domestic, industrial and rural run-off into waterways carrying high levels of nutirents, as well as stock stirring up sediment that would normally remain undisturbed.
In the evolutionary model of origins, humble pond scum holds an important position, since evolutionists believe that cyanobacteria was amongst the earliest life on Earth and was therefore the ancestor of all other life, including humans. James Horgan, for example, said that "We are all animals, descendants of a vast lineage of replicators sprung from primordial pond scum". Creationists have used these views to highlight that evolution teaches that humans evolved from pond scum, in much the same way as others might humorously reduce the theory to humans evolving from monkeys. The 'primordial soup' thought by many to be the origin of life is not a remote concoction of another age but rather is still with us, and is to be be found quietly photosynthesising in ponds and pools almost anywhere one cares to look for it.
"Pond scum" has come to be an insult for anyone considered an exceptionally low person. According to Ken Levine, a television comedy writer who worked on the show, the term originated on an early episode of Cheers titled "The Coach’s Daughter". In this episode, Diane (Shelly Long) described a particularly obnoxious person as "pond scum".
- ↑ Pond scum in the Merriam-Webster dictionary.
- ↑ Horgan, John, "The New Social Darwinists", Scientific American, October 1995, pp. 175–176, quoted by Ham, Ken, Darwin’s Sad Legacy, 23 March 2009.
- ↑ See for example various reader comments on Internet forums  (Content warning: These pages may contain offensive content.)
- ↑ Ken Levine, The biggest laugh you never saw on CHEERS, 22 May 2008, and Ken Levine, Let Steve Jobs determine YOUR sexual preference!! 19 July 2010. (Content warning: These pages may contain offensive content.)