I’ve said 99 percent of beneficial mutations are function compromising. This is due to the fact there are many ways to break something relative to the few ways of making something.
Also, the pan-genome of E. Coli for example shows pressure to:
- either lose genes
- not acquire them through plasmid exchange
There is a lot of pressure to lose parts of no-immediate use. That is powerful force of adaptation. Some have said only 20% of E. Coli’s genomes are conserved. Here a figure of its pan genome, but it shows what 20% means approximately:
I got the 99% figure regarding function-compromising beneficials from a presentation by Michael Behe to a private group. I didn’t realize perhaps that Behe might officially only suggest 90% in public. If he’s said 99% somewhere publicly, I’d be happy to cite that. The 90% figure was in his response to Lenski’s criticism of Darwin Devolves.
Other’s are welcome to supply what they think the proper figure should be.
If we say, “we don’t know the percent of function-compromising beneficials are”, then one should consider the implications for evolutionary theory if “we don’t know” or even have a good guess as to what this figure is, because this implies “we don’t know” some important features about the evolution of complexity.