{ "export": { "source": "https://urth.darkrealm.vip/thread/urth/811", "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": 811, "subject": "Moths and Darwin", "messages": 1, "voices": 1, "first": "1998-06-16T09:26:32+00:00", "last": "1998-06-16T09:26:32+00:00" }, "messages": [ { "message_id": "", "from": { "name": "Mark Andersen", "address": "manderse at nmsu.edu" }, "date": "1998-06-16T09:26:32+00:00", "subject": "(urth) Re: Moths and Darwin", "in_reply_to": null, "reply_link": null, "blocks": [ { "kind": "quote", "depth": 1, "text": "From: David_Lebling at avid.com\nFrom: Dan Parmenter \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?\nI 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." }, { "kind": "text", "depth": 0, "text": "Yes. This is the crucial point. Natural selection relies on variability andworks\nat the population level -- Lamarckism doesn't need variation\nbetween individuals, and works at the individual level. Here's my\nReader's Digest Condensed Version of natural selection: While on the\n_Beagle_, Darwin noticed three things about plants and animals:\n1) Individuals of plant and animal species are as different as individual\nhumans.\n2) These differences are heritable.\n3) Sometimes, these differences are differences in traits that\ncan influence survival and reproduction.\nNatural selection is NOT a hypothesis or theory to explain these three\nphenomena. Rather, it is the inevitable logical consequence of these\nphenomena, in the same way that the conclusion of a mathematical\ntheorem is the inevitable logical consequence of its assumptions. Failure\nto realize this has led to lots of unnecessary conflict between biologists\nand non-biologists, and among biologists as well. This same failure of\nunderstanding also led Popper to the erroneous conclusion (which he\nlater retracted, by the way) that evolutionary biology is not science,\nbecause it does not make predictions." }, { "kind": "quote", "depth": 1, "text": "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." }, { "kind": "text", "depth": 0, "text": "Exactly. This is the way natural selection works: by shifting the mean ofa trait\n(or the fractions in the population that show discrete traits)." }, { "kind": "quote", "depth": 1, "text": "If 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." }, { "kind": "text", "depth": 0, "text": "Yes again. Natural selection can exhaust genetic variation." }, { "kind": "quote", "depth": 1, "text": "There are no simple statements about genetics." }, { "kind": "text", "depth": 0, "text": "Well, maybe. Certainly true once you get past Punnett squares andone- or\ntwo-locus two-allele systems with dominance." }, { "kind": "quote", "depth": 1, "text": "If 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." }, { "kind": "text", "depth": 0, "text": "If the alleles for red coloration are there in the population. If not, the\nmoths might have to become cryptic in some other way. Perhaps\nselection might favor small-bodied moths that could hide in cracks\nin the tree bark, for instance. If the genes for the ideal solution aren't\navailable, natural selection can usually manage to jury-rig something\nthat works. Or not (which is one cause of extinction).\n\nBy the way, I like the idea that the noisy thing in the Saltus mine is\nsome kind of machine. Here's one hypothetical time line: During the\nFirst Empire (or the Age of the Monarchs), the underground treasury\nis established, with a mechanical guardian (or several) to keep an eye\non things. Life goes on above ground, the farming village of Saltus is\nfounded, and the regime that supported (or needed) the underground\ntreasury passed away. Later, as the sun begins to die and the climate\nbegins to worsen and the crops begin to fail, someone (who, I wonder?)\nadvises the good people of Saltus to take up mining and the first shaft\nis sunk, by chance (perhaps) near the underground treasury. At the\nbeginning of the Age of Autarchs, the young cacogen Inire discovers the\nundergound treasury and assigns some guardians of his own to keep an\neye on it.\n\ncheers,\nMark A. (Buteo)" }, { "kind": "sig", "depth": 0, "text": "Dr. Mark C. Andersen, Department of Fishery and Wildlife Sciences\nNew Mexico State University, Las Cruces, NM 88003-0003\nvoice:(505) 646-8034 FAX: (505) 646-1281\nmanderse at nmsu.edu, http://leopold.nmsu.edu/manderse/markhome.htm" } ] } ] }