Trying to identify a very old story that involved human colonists who land on a distant earth-like planet and find human survivors of a much earlier colonizing attempt. The new colonists discover that while their own enzymes are based on common L-isomers, the survivors have evolved and mutated so that their enzymes are R-isomers (L- and R- denote opposite chiralities). It turns out that the food brought by the new colonists cannot sustain the survivors and the planet's natural food supply cannot sustain the new colonists.

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    en.wikipedia.org/wiki/Chemical_chirality_in_popular_fiction - There are a couple of scifi stories in the list; Larry Niven's Destiny's Road, Marti Steussy's Dreams of Dawn
    – Valorum
    Commented Jun 25, 2015 at 20:40
  • Already checked those titles. Anything else?
    – rabble58
    Commented Jun 25, 2015 at 20:54
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    OK. Both of those stories broadly match what you're looking for. A) Could you be mistaken? B) What about these stories was wrong? Has this prompted any further recollection? Character names, when you read it, how do you know that it's old, any specific phrases?
    – Valorum
    Commented Jun 25, 2015 at 21:35
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    This rings a bell. Do the survivors all look alike?
    – Beta
    Commented Jun 26, 2015 at 2:31
  • Actually not my question. Asking for a friend. He says, Probably a short story, probably from the 1960s or 1970s or older. Can't remember anything else.
    – rabble58
    Commented Jun 26, 2015 at 13:41

2 Answers 2


"Contagion" by Katherine MacLean. See this answer for details.


In A Small Colonial War (1989) by Robert Frezza, the protagonists are soldiers trying to keep the peace between the second and third wave of colonists on such a planet and meddling corporations. The first wave of colonists has mostly died by the time of the novel. The intelligence officer explained how successive waves of colonists were better prepared to deal with the alien biochemistry.

  • Does not sound like the right story and it's not old enough. Story is most likely from the 1960s.
    – rabble58
    Commented Jul 6, 2015 at 18:06

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