That's true--and may account, in part, for the high miscarriage rate in humans (an average 20-percent noted, perhaps as high as 60-percent, with most occurring in women who don't even realize that they are pregnant).jim stone wrote:There;s the objection that the vast majority of mutations are detrimental.
It's easy enough to spot a fully lethal mutation (one that causes death directly, such as being born without a stomach). It's much more difficult to spot neutral mutations.
However, neutral--or even slightly detrimental--mutations can become favorable when conditions change. The classic example is the British peppered moth (Biston betularia). This moth was generallywell-camoflaged on light tree bark, but there were constant mutations leading to some darker-than-normal individuals that were not as well-camoflaged. Some of the darker moths were spotted by birds and eaten (at a greater rate than the lighter moths). Some managed to survive.
As pollution due to factory soot increased in the early 1800s, the trees in the Birmingham area were darkened with soot. As a result, the normal light-colored moths began to stand out, making them easy prey for birds, while the situation of the darker moths became safer. Over many years, the proportion of dark moths became very high, while the light moths became rare (but never totally extinct).
The story doesn't end there, though. As the factory pollution was cleaned up, the situation was again reversed, and the light moths prospered again, while the dark ones once more began to become rare.
Try this link to the html version of a PDF file, by Bruce S. Grant to see the kind of evidence and reasoning involved. While creationists have attacked the legitimacy of the peppered moth example by questioning a particular set of experiments performed by H.B.D Kettlewell in the '50s, note the following:
"Textbook accounts of industrial melanism too often dwell in the past. They begin with
pre-industrial England and end with Kettlewell. As a footnote they might add that melanism has
been on the decline in recent years following clean air legislation. Yet, it is the record of the
decline that is by far the strongest. During the last century and the early part of this one few
people kept records about morph frequencies, so our picture of the rise and spread of melanism is
sketchy. Documentation for the decline in melanic frequencies is vastly more detailed (e.g.,
Clarke et al. 1994, Cook et al. 1999, Grant et al. 1996, 1998, Mani and Majerus 1993, West
1994). No other evolutionary force can explain the direction, velocity and the magnitude of the
changes except natural selection. That these changes have occurred in parallel fashion in two
directions, on two widely separated continents, in concert with changes in industrial practices
suggests the phenomenon was named well. The interpretation that visual predation is a likely
driving force is supported by experiment and is parsimonious given what has been so well
established about crypsis in other insects. Majerus allows that the basic story is more
complicated than general accounts reveal, but it is also true that none of the complications so far
identified have challenged the role assigned to selective predation as the primary explanation for
industrial melanism in peppered moths. Opinions differ about the relative importance of
migration and other forms of selection. It's essential to define the problems, to question
assumptions, and to challenge dogma. This is the norm in all active fields of research. Majerus
has succeeded admirably in communicating this excitement to the reader. I would add this: Even
if all of the experiments relating to melanism in peppered moths were jettisoned, we would still
possess the most massive data set on record documenting what Sewall Wright (1978) called
'…the clearest case in which a conspicuous evolutionary process has been actually observed.'"
The point of all this is that, with the exception of fully lethal mutations, it is impossible to judge whether any particular mutation will end up being favorable or detrimental in the long run.
But, of course, speciation has nothing whatsoever to do with "increasingly complex features". Speciation could just as readily involve a decrease in complexity--or none at all. Speciation is about nothing more than changes in the selection of reproductive partners.What's needed for the emergence of species with increasingly complex features, are lots of beneficial mutations.
But once speciation occurs, each species is on its own evolutionary track, and there is nothing to hold back divergence. In contrast, again using dogs as an example, the differences found in any particular individual or small group of closely related individuals can be submerged in the overall gene pool and never have any serious effect on survival of a population. If a litter of striped cocker spaniels were to be born one day, the chances of that mutation becoming common (without human intervention) is low. But in a small reproductively isolated population, it might become the norm within a couple of generations, depending only on how it affected--or failed to affect--fitness for the current environment of that population.
Yet random mutation has produced a vast variety of dogs--mostly within just a couple of thousand years. (Dog breeders can't breed for a characteristic that never occurs.) And, as my example of the Mexican Hairless and the St. Bernard shows, that variety is already sufficient for the beginning of speciation.ID maintains that random mutation can't do it, because the probabilities of this happening at random are too low--and of course it would have to happen not just once or twice, but continually.
You'd think that "intelligent" design on the part of an omipotent deity could come up with better designs than the ones we're stuck with now. If an engineering firm had designed my body, I think I'd ask for my money back. No need to even mention my wife, 5'2", 75 pounds, half-paralyzed, in almost constant pain, barely able to swallow, with a 10-inch bed sore, memory loss, and dementia. Who would purposefully create a body prone to such failure?
(By the way, if 60 percent of all human fetuses are miscarried, then do their souls just get to go directly to Heaven without all this free will and original sin nonsense that the remaining 40 percent of us have to put up with? It hardly seems fair, does it?)
