[MineralMan]

"I learned in 1962 in Biology 101 that most mutations are deleterious (e.g., lethal) and, furthermore, whether a non-lethal mutation is "beneficial" depends upon the conditions within the envronment, which is continuously changing."

There are also many mutations which are seemingly without any effect at all, good or bad. The whole point is that there are some that are beneficial to the organism. That's all it takes for evolution to proceed. Some.

[muawiyah]

The point is that it doesn't seem to be mutations at all that result in serious changes in the genome ~ rather, it's reshuffling of existing genes, or replications of existing genes, that bring about the greatest degree of change.

Viable mutations are, to say the least, rare!