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The "Other Flagellum" Is Also a Design Wonder


Arguments for intelligent design have long made use of the bacterial flagellum as a visual aid for Darwin-challenging design. It's the one with the rotary engine (well illustrated and accessibly explained in the documentary Unlocking the Mystery of Life). Eukaryotic flagella (the kind that beat back and forth) look simple by comparison. But here's what researchers from Brandeis University say about them:

Eukaryotic flagella, whip-like organelles that elegantly propel microorganisms and pump fluid, seem to embody simplicity on the microscopic scale. But appearances can be deceptive: Flagella are composed of 650 different types of proteins.

Their jobs are vitally important. Flagella help sperm swim, sponges eat, and sweep mucus from the lungs, among other functions. Their length depends on their purpose but flagellas' structure and rhythmic, beating movement remain the same across functions and species.

That fluid movement is a highly sought-after capability in small-scale devices, such as microrobots. But scientists have struggled to build a simple, controllable model that can recreate it. (Emphasis added.)

It's a struggle, all right. The Brandeis team succeeded in getting some non-biological material to beat back and forth, but only in a computer model. And in their model, they used only simple components arranged like a string of beads. Even then, they had to figure out the proper spacing, length, and strength of attachment to make them move. Physicist Michael Hagan was glad enough just for that:

"Because this system is so simple, and its construction so different from that of flagella, we should be able to elucidate the most fundamental features of flagella that give rise to and control motion. These features can be understood without having to unravel all 650 moving parts of a flagellum," Hagan says.

Here we see human designers struggling to grasp just the fundamental features of the eukaryotic flagellum. That makes this story doubly supportive of the theory of ID: (1) design detection: recognition of the complex arrangement of parts for function, and (2) biomimetics: motivation to understand the design and imitate it.

The eukaryotic flagellum, by the way, is similar in design to the cilium -- another ID mascot in Michael Behe's books. "Flagella" in eukaryotes usually refer to longer filaments that propel single cells like sperm or protists, whereas "cilia" are typically shorter, arranged in stationary tissues, and work in concert. Eukaryotic flagella also have simpler back-and-forth beating motions compared to cilia, which employ a power and recovery stroke in three dimensions.

Image source: Wikipedia.