Anyone knows what a flagellum is? Look at the picture below. It is like a whip-like structure that propels some type of bacteria around. According to the proponents of intelligent design, a flagellum is proof of a creator as according to them if you remove one piece of the structure them it is rendered useless. So how can this have evolved? But again, when it comes to reality, intelligent design is always in the wrong. Scientists have discovered a bacteria with a structure very similar to the flagellum but with many missing parts and the structure has a function! It is used by bacteria to inject toxin in its hosts. This basically destroyed the irreducible complexity theory so love by Intelligent design proponent.
It could've come from many of the numerous trans-membrane proteins used for transporting substrates against concentration gradients, and there are some ideas about how this process could have happened in the current body of knowledge. The problem with this argument is that it relies on trying to claim that evolution cannot be responsible for things that are seemingly useful and complex, but it most certainly can. Evolution isn't goal oriented and it constantly tinkers to improve fitness(i.e adaptability & suitability). With that combination all you need is some time.
Indeed, in fact if you selectively remove 40 parts of the flagellum and leave 10 parts, you can get a type III secretory system! They said the same thing about the eye but they were again wrong. The most basic of eyes that can only detect light and dark is still useful but not as efficient as, say, a human eye. The Irreducible Compexity hypothesis, which is ID proponents' brain child, cannot hold.
In the Spirit of Sankofa, .......On the argument, Flagellum Unspun: Collapse of Irreducible Complexity, there is counter argument submitted by Dembski and Behe; Still Spinning Just Fine: A Response to Ken Miller. But more to the problem in this debate would be Behe’s attempt at having the concept, Intelligent Design (ID), to be considered as science, when he doesn’t name the Designer, as Paley did. It is Behe’s very definition of irreducible complexity that challenges Miller and the others to show systems such as the flagellum, the eye, blood coagulation and the immune system are constructed from small changes, singularly; in order to be falsified. So, no wonder the NAS doesn’t accept ID as science, there’s not enough generational time to refute. Meanwhile neither the scientific community nor the biological community is able to explain how such systems arose in the first place through evolutionary means, other than subject to the criticism of genetic algorithm. http://www.designinference.com/documents/2003.02.Miller_Response.htm Peace In,
Why such system arose? For locomotion. And the article is old and weak. See quote below. They've found an intermediate system (a couple of year or so ago) between the TTSS and the flagellum and it is also used to inject toxin into hosts cell. So evolution is clearly the only and logical explanation! The gap will clearly close further and further. This guy explain this. Accordingly, the TTSS may be thought of as a possible subsystem of the flagellum that performs a function distinct from the flagellum. Nevertheless, finding a subsystem of a functional system that performs some other function is hardly an argument for the original system evolving from that other system. One might just as well say that because the motor of a motorcycle can be used as a blender, therefore the motor evolved into the motorcycle. Perhaps, but not without intelligent design. Indeed, multipart, tightly integrated functional systems almost invariably contain multipart subsystems that serve some different function. At best the TTSS represents one possible step in the indirect Darwinian evolution of the bacterial flagellum. But that still wouldn't constitute a solution to the evolution of the bacterial flagellum. What's needed is a complete evolutionary path and not merely a possible oasis along the way. To claim otherwise is like saying we can travel by foot from Los Angeles to Tokyo because we've discovered the Hawaiian Islands. Evolutionary biology needs to do better than that.