{
  "export": {
    "source": "https://urth.darkrealm.vip/thread/urth/797",
    "note": "Exported from an unofficial mirror of a public mailing list. Copyright in each message remains with the person who wrote it.  Email addresses are obscured as `user at host`, the form the original archive published. This file was rebuilt from parsed fields rather than retained headers, so it is faithful in content but not byte-exact.",
    "addresses": "obscured as 'user at host'"
  },
  "archive": "urth",
  "thread": {
    "id": 797,
    "subject": "Moths",
    "messages": 1,
    "voices": 1,
    "first": "1998-06-15T17:18:59+00:00",
    "last": "1998-06-15T17:18:59+00:00"
  },
  "messages": [
    {
      "message_id": "<urth-v0013-0073@digest.urth.net>",
      "from": {
        "name": "David_Lebling",
        "address": "david_lebling at avid.com"
      },
      "date": "1998-06-15T17:18:59+00:00",
      "subject": "(urth) Moths",
      "in_reply_to": null,
      "reply_link": null,
      "blocks": [
        {
          "kind": "quote",
          "depth": 1,
          "text": "From: Dan Parmenter <dan at lec.com>\nWhat would Dollo have to say about that?  Did the Peppered Moths' (as\nthey are called) coloration actually \"revert\" or did they simply\nevolve their white color a second time?  If we introduced large\namounts of red soot into their environs could they evolve into red\nmoths (Cayenne Peppered Moths) or is the range of possible mutations\nonly black and white?"
        },
        {
          "kind": "text",
          "depth": 0,
          "text": "I think the general explanation that is given in genetics textbooks is\nnot that the moths \"evolved\" a black color and then a white color.\nRather, there was (and is) a certain amount of genetic variation in the\nmoth population.  When pollution made the trees dark, there was\nselective pressure that favored darker colored moths (i.e., birds found\nand ate the light-colored ones).  So, after a while, the population was\nmostly dark-colored, but this didn't mean that the gene for\nlight-colored-ness disappeared: it just got less prevalent.  Eventually,\nthe pollution was cleaned up and the selective pressure went the other\nway, as the dark moths became more noticeable, so the occasional light\ncolored moth was able to reproduce, leaving more light colored moths,\nand so on.\n\nIf the soot had gone on long enough, it is possible to imagine that\nevery light colored moth would have been eaten, in which case when the\ntrees turned white again, that species of moth would have been in a\nmajor pickle.  Of course, some characteristics are caused by random\nmutations that happen at \"favorable\" sites in the chromosomes, and these\nhappen over and over, \"spontaneously,\" but color in moths may not be one\nthem.  Some genetic diseases are like that, but it gets even more\ncomplicated, because the tendency to get some of these diseases is\ninherited (not the certainty, the tendency), so maybe these favorable\nspots are themselves a genetic variation.\n\nThere are no simple statements about genetics.\n\nIf there is some representation of cayenne pepper genes in the moth\npopulation, then eventually dyeing the trees red will create selective\npressure favoring red moths.  Otherwise, you're in the position of\nwaiting for the moths to mutate at random into red.  This is roughly as\nlikely as turning a mouse's tail into a hand by slapping it against a\ntree.\n\n     -- vizcacha\n     (david_lebling at avid.com)"
        }
      ]
    }
  ]
}