On another thread we have been discussing abiogenesis in particular, but there was also some discussion about the evolution of an irreducibly complex system. Commenter CHartsil indicated that “we actually watched an IC system evolve” in reference to Lenski’s E. coli research. At my request, he has posted a brief summary of the research and his take, which I am now elevating to a new thread on this important topic.
For those who disagree with CHartsil’s take, strong objections on substantive grounds are of course welcome, whether relating to Lenski’s research or CHartsil’s interpretation of it, but not irrelevant personal attacks. Thank you.
Guest Post by CHartsil:
This is a pro-ID board so I doubt I need to explain irreducible complexity. When arguing against it, most will bring up Ken Miller or Nick Matzke. They have great points but theirs are indirect and theoretical pathways for systems considered IC. That’s why I’m fond of Lenski’s cit* E. coli.
This particular strain of E. coli evolved the ability to metabolize citrate aerobically. While most E. coli can do this anaerobically, part of the definition of wild-type E. coli is actually the inablity to use citrate as a substrate aerobically. This may not have been a terribly fascinating addition of function if not for the frozen fossil records kept by Lenski et al.
These frozen generations allowed Lenski to determine that this trait was not acquired via a single mutation as it could only be repeated after generation 20,000. Given the distinct cladistic division amongst the populations at the border generation, it was determined that there were at least two potentiating mutations prior to the cit* event.
In this third clade a tandem duplication resulting in a novel regulatory module leading to the aerobic cit* could be repeated and verified. It has been noted since that the fitness of the population has been improving without notable upper limit, increasing based on the number of copies of the new regulatory module.
I find this to be sufficient in warranting the dismissal of the concept irreducible complexity. In Lenski’s E. coli, we observe the rise of a new function resulting from a new gene and new gene regulation. This function is comprised of now interdependent components which demonstrably did not exist in parent generations. It is by definition irreducibly complex and it was observed to evolve.
Nota bene: for purposes of the above discussion, CHartsil is using the following definition of irreducible complexity: “a system comprised of interdependent parts, the removal of any of which will cause the system to cease functioning.”