Free2B said:
But how does a mutation become the norm? It obviously has to provide a benefit to the species. And then has to breed with other members. And this mutation has to be a dominant trait, which most mutations are not. (If you cite the bacteria thing again, I'm going to scream. Let's talk about something that isn't asexual, and hopefully on a bigger scale.)
Ok, here is something which isn't asexual, Saccharomyces cerevisiae, bakers and brewers yeast. Used in the scientific community as model system for understanding cellular processes performed in eukaryotic cells (cells with nuclei - just like human cells, etc). Many human genes have very similar genes in yeast - more so, if the gene is essential for supporting life.
Real world example: The yeast can contain two different forms of the same gene - both are mutant, preventing the yeast from growing without the external addition of this particular nutritional compound - arginine (an amino acid).
The spontaneous mutation rate, to cells that can now grow happily without arginine is about 1 in 10,000. This mutation rate occurs purely as a result of tiny errors during the copying process of its DNA every time the cell duplicates itself. Now, 1 in 10,000 may sound a rare, but bare in mind just how small a single cell is, and how rapidly it divides: On average you would get your first mutant after only 14 generations - it would take less than a day for this to occur - in much less than 1ml of liquid.
If the environment suddenly became devoid of arginine, the yeast would have evolved in less than 24 hours. And this would be the ONLY yeast surviving. It would no longer me considered mutant - it would BE the new species.
But this is only for this one gene. The changes can be occurring randomly in all parts of the yeast genome at similar rates. In all genes. Some mutations will be silent. Some will be beneficial. But only the deleterious mutations (in a given environment) will not be propagated to the daughter cells.
Now, you could argue that the likelihood of getting two PARTICULAR spontaneous mutations is very low. 10,000 x 10,000 => 1 in 100,000,000. But it would actually only take 27 generations to achieve this randomly. It occurs in a yeast culture every 2 days. Three simultaneous PARTICULAR mutations would take 40 generations - 3 days.
But the point is that evolution does not dictate that PARTICULAR genes be modified. It is random - solutions to an environmental pressure can come about from completely unexpected combinations of otherwise silent mutation, which are occurring continually WITHOUT selection.
Thus if you required 1000 specific simultaneous mutations to occur, you would only need to grow the yeast - from a single cell - in nonselective conditions for 1000 days, and then apply the selection. Now that's less than three years: About 1 billionth of the time since "life" began.
Since the yeast is a sexual organism (just like us), it has even better chance of success, because it can freely interbreed with other members in a completely random way permitting the rapid accumulation, or loss, or recombination, of different mutations, which some of the time may become beneficial, and serve as a selective advantage over others. This line would then become the prevalent strain.
Given enough time, and appropriate selection, the yeast will not resemble its ancestors. Has it become a new species? Only if the original species coexists and is sufficiently different to prevent interbreeding with the new form. This, in fact, is a critical aspect to the origin of a new species: The inability to interbreed is not only used to define a new species, it also permits subsequent additional differentiation of the two lines. And on and on it goes...
Now in response to your specific question about monkeys...(I think you mean apes):
Free2B said:
For instance, what first caused a monkey to stand upright?
Selective advantage
Free2B said:
And why was that a surviving trait?
Selective advantage
Free2B said:
And are you sure that other members of the population would want to breed with an outsider?
It is not about what they want or what they don't want: If the new characteristic had a selective advantage then it will be propagated.
This discussion is way off topic, but quite compelling. Maybe it should be moved?