Evolution is good at creating niche advantages by breaking things; it isn’t good at building fundamentally novel forms.
Michigan State University biologist Richard Lenski and collaborators have just published a terrific new paper.
Right now, within your bodies this little engine is cranking away. Without this machine, oxygen-dependent life could not exist.
Lenski agrees that the beneficial mutations seen in his Long Term Evolution Experiment are overwhelmingly degradative or loss-of-function ones.
Their review pretty much completely misses the mark. Nonetheless, it is a good illustration of how sincere-yet-perplexed professional evolutionary biologists view the data.