Trust our stalwart physics color commentator Rob Sheldon to draw the logical conclusion about horizontal gene transfer between plants and insects: If plants and insects can exchange genes (and who knows what else can?), what are we to make of dogmatic claims about universal common descent? He writes,
If I said, the “Universal Law of Gravity” states that all matter attracts other matter through the Newton’s inverse square law, then if I found an exception, the entire law is broken. You couldn’t even say, “most of the time it works barring a few exceptions.” The Universality of the law is the problem. We would have to figure out why the exceptions were exceptional, and until we knew why, all we could say is that there is no Universal law to discuss–it has become a Special Law of Gravity.
For Universal Common Descent, we can say that all life, everywhere on the planet Earth MUST have come from some common ancestor, because it is a Universal law. We don’t have data on those ancient ancestors, but we can rely on the Universality to derive their previous existence. Once there is an exception, once there is a critter that did NOT have a common ancestor, then it is no longer a Universal law, and we can no longer rely on its Universality in our logic syllogisms. Even worse, we know that waiting for a random event to turn lizards into chickens is going to be a loooong wait, whereas transporting the chicken or stealing the chicken genes can be done in a very brief moment. In the statistical sense, the pathway of random mutating evolution is a set of measure zero when contrasted with all the other available pathways of making a chicken. In Mike Behe’s example, if there are a billion ways to break a gene, and only one way to improve it, which event will occur first and with what probability? So losing the Universality of common descent isn’t a slight inconvenience, it is universally deadly to the theory.
Which is why those that need the theory for other philosophical reasons, won’t give it up without a fight.
See also: Horizontal gene transfer between plants and insects acknowledged. So what becomes of all the Darwinian casuistry around “fitness” and “costly fitness” if things can happen so simply as this? The article emphasizes the benefits of studying “evolution.” Indeed, but that can’t mean fronting Darwinism 101 any more.