Why not use bacteria as your example. I think they burn through a generation every 30 min or so, don't they? It's an apples to oranges comparison though. The far more simpler genome of the fruit fly (or of bacteria) means less can go wrong plus they have an enormous population size anyways (unlike us).
Not really. Because of their rapid generation times, bacteria and to a lesser extent, fruit flies are under significant constraints to keep their genome small and compact. This provides for efficient, rapid duplication and conserves resources. If you look at a bacterial gene map, you would see that there is very little untranslated regions. The following table is a very generalized overview:
|
|
E. coli
|
Fruit Fly
|
Human
|
|
# genes
|
4,500
|
15,700
|
20,000
|
|
# base pairs
|
4.6 M
|
139.5 M
|
3,235 M
|
|
# chromosomes
|
1
|
4
|
23
|
Gene density is not a straight forward calculation, however. For E. coli, the average distance between genes is about 120 base pairs. Humans can have 10s of thousands of base pairs between genes. Also, about 25% of the human genome is introns, which are spliced out and recycled (some introns do have functions so ~20% are discarded). E. coli does not have introns.
The point is that the human genome has huge areas where mutations could occur that would have no effect on fitness. Mutations would be much more likely to affect fitness in bacteria. So their "simpler genomes" means more can go wrong.
If something does go wrong, then natural selection should spot it right away and remove it. The near neutral theory, however, allows for slightly deleterious mutations to squeak by, unnoticed by natural selection.
You seem to imagine natural selection as an active agent that constantly scans the genome for defects so it can remove them. Not so. If a fruit fly was born with one leg that was 25% shorter than the others, that would probably be a slightly deleterious mutation, right? But... would that stop him from finding a mate and producing offspring? Probably not. So he mates and the female lays 1,000 eggs, roughly half of which have this slightly deleterious mutation. This would be how slightly deleterious mutations "squeak by, unnoticed by natural selection." The question should be "Will the mutation affect the organism's ability to produce offspring?" That is how fitness is determined by natural selection.
I like uphill battles.
Do you like uphill battles just for the sake of uphill battles? I hope you are the kind of person who is willing to learn a few things rather than just wanting to rage against something you don't like or don't understand.
HBD
Whoever calls me ignorant shares my own opinion. Sorrowfully and tacitly I recognize my ignorance, when I consider how much I lack of what my mind in its craving for knowledge is sighing for... I console myself with the consideration that this belongs to our common nature. - Francesco Petrarca
"Nothing is easier than to persuade people who want to be persuaded and already believe." - another Petrarca gem.
Ignorance is a most formidable opponent rivaled only by arrogance; but when the two join forces, one is all but invincible.
™ Version 4.2
