Joined: May 2006
|Quote (mammuthus @ June 11 2009,18:08)|
|Quote (deadman_932 @ June 11 2009,15:57)|
|Sanford's "genomic (mutational) meltdown" scenarios are a hoot. Even DaveScot was bright enough to see that Sanford's proposed mutation rates were out of line with reality: fast-reproducing sexual species that have existed a few million should have all been extinct by now, but they're not. Sanford inflates deleterious mutation rates and disregards compensatory mechanisms.|
His argument is a little more involved than that. It seems to revolve around genome size; the smaller genome size of something like P.falciparum prevents genetic meltdown, but it would occur with larger genome sized mammals. So genetic entropy is a problem for the latter (if not on Sanford YEC timescales). You can't just take fast reproducing things like P.falciparum and apply the Genetic Entropy failure in this case widely. At least that's how I read it.
Well, Wes mentioned one example of "large" - genomed rapidly-reproducing species, and there's a lot more available. Mammal genomes average between 2 and 3 gigabases (Gb) but lots of insect and plant genomes (like wheat) can be larger: around 16 Gb in wheat or grasshoppers (Podisma pedestris) -- five times larger than humans.
Nailing Sanford down on questions about interesting populations like california condors would be fun -- they're the only North American remnant of Gymnogyps, been around since the early Pleistocene and their population dropped down to 22 individuals not very long ago... and their est. genome size is 1.5 Gb. They should have accumulated enough deleterious mutations so that such a small closely-related group would produce nothin' but dead young, right? Or how about Przywalski's horse?
Sanford is a YEC of sorts, so he skewed his parameters to fit his skewed view of the Earth's entire biome being less than 100 K years old, as I recall ( I may be wrong with the exact figure there).
ETA: I was curious about known recessives in the existing condors and there is one identified (chondrodystrophy) that results in fatal abnormalities :
J. Geyer, O.A. Ryder, L.G. Chemnick and E.A. Thompson, Analysis of relatedness in the California condors: from DNA fingerprints, Mol. Biol. Evol. 10 (1993), pp. 571–589
Romanov MN, Koriabine M, Nefedov M, de Jong PJ, Ryder OA (2006) Construction of a California Condor BAC Library and First-generation Chicken-condor Comparative Physical Map as an Endangered Species Conservation Genomics Resource, Genomics, 88 (6), 711-8
AtBC Award for Thoroughness in the Face of Creationism