Successful production of a 200-component functioning organism requires at
least 200 beneficial mutations. The odds of getting that many successive
beneficial mutations is r200, where r is the rate of beneficial
mutations. Even if r is 0.5 (and it is really much smaller), that makes
the odds worse than 1 in 1060, which is impossibly small.
Morris's calculation assumes that all the beneficial mutations must
occur consecutively with no other mutations occurring in the
meantime. When one allows harmful mutations that get selected out
along the way, 200 beneficial mutations would accumulate fairly
quickly -- in 200/r generations using the assumptions of Morris's
model. (The real world is quite a bit more complicated yet. In
particular, large populations and genetic recombination via sex can
allow beneficial mutations to accumulate at a greater rate.)
