Haven't Experiments Demonstrated Major Evolutionary Innovation?
Laboratory evolution experiments have produced substantial adaptation and, in some cases, striking new phenotypes. The Lenski long-term evolution experiment, for example, produced a population of E. coli capable of exploiting citrate under aerobic experimental conditions. If evolutionary innovation can be observed directly, why question the creative power of evolutionary mechanisms?
Why This Matters
Experimental evolution is especially valuable because researchers can observe populations over many generations, preserve ancestral samples, identify mutations, and test proposed historical pathways. These experiments therefore provide unusually direct evidence about what evolutionary mechanisms can accomplish.
Response
Such experiments should be accepted for what they demonstrate. The citrate-utilizing E. coli acquired a significant new metabolic capability, and later research identified genetic changes involved in establishing and refining that phenotype.
The further question concerns scope. A new metabolic capability in bacteria and the origin of a new organ, developmental architecture, or animal body plan are not identical biological problems. Experimental demonstrations establish real evolutionary capabilities, but the relevance of those capabilities to larger historical innovations must be examined rather than either dismissed or assumed.
Question That Remains
Which experimentally demonstrated mechanisms can be connected to particular large-scale historical innovations, and what additional developmental or organizational changes would those transitions require?