Biology: Mission Impossible

In the famed American TV show, Mission: Impossible, each episode began with a scene in which the leader of the Impossible Mission Force (IMF) received instructions for their next assignment. It was made clear in the message that the government would completely disavow any involvement with the IMF should they be caught, and consequently, after the tape had been played it would self-destruct. And so it did – every episode – it went up in smoke. In that process, if we are technical, it really wasn’t the tape itself that self-destructed: there was some mechanism built into the system that would destroy the tape. And so it is in biology. Within living systems there are several self-destruct mechanisms found at the biochemical, cellular and organismal levels which warrant our attention.

Before a cell can divide, it must make a copy of its DNA – the operating instructions of the cell. To do so first requires a partial deconstruction of the molecule. The molecule must first be unwrapped from around associated proteins known as histones. Next, an enzyme relaxes the coiling inherent in the molecule. Then another enzyme is used to break the hydrogen bonds which link the base pairs in the molecule – breaking the rungs of the ladder. If the process stopped here, the DNA would be functionless, and it would be an end-of-life situation for the cell. Normally, the process continues with the help of other complex nano-machines which bind matching nucleotides to each of the exposed bases in the strands, and seal up the new sugar-phosphate backbone.

Once a cell has a full copy of all its DNA it can move forward toward the complete division of the cell which requires the segregation of the two sets of DNA. To accomplish this requires yet another deconstruction. Each cell possesses a network of microtubules known as the cytoskeleton which is essential for inner-cell transport of molecules. As a cell enters into the cell division process, this cytoskeleton is completely destroyed. If the process came to a halt at this point, it would also be an end-of-life situation for the cell as the cell would be unable to deliver important molecules to the correct locations needed to function properly. Instead, the cell will take the broken sections of microtubules and reassemble them into parallel tracks, known as spindle fibers, running from one pole of the cell to the other. As chromosomes separate, the motor proteins bound to each chromosome will walk its way along the spindle fibers toward the pole, destroying it once again as it moves. Once the cell has divided into the two new cells, the cytoskeleton is reconstructed from the broken pieces of microtubules.

On a much more complex level, self-destruction occurs during the life cycle of insects with complete metamorphosis (i.e. egg, larva, pupa, adult). When that very hungry caterpillar develops into its chrysalis, everything seems to go quiet. Metabolically, though, this is the most active time in the life of this insect. It is undergoing tremendous transformation. If you open the chrysalis early on in the pupal stage, you are likely to find it has all become a seemingly lifeless goo.  Metamorphosis does not involve simply a modification of existing parts; it entails the complete destruction of every body system of that insect. In the midst of that morass, though, are regions referred to as imaginal discs from which entirely new systems develop and form together to create the adult organism.

In each one of these cases there is a built-in, complex system which destroys biological material and by itself would result in an end-of-life situation. Fortunately, there are subsequent complex systems which rectify the destruction process. The presence of these mechanisms is very problematic to a Darwinian explanation of development. This insists new structures and processes are expected to emerge from small gradual changes. Each of these changes should either have a neutral or positive effect on the survival advantage of the species. But if the first processes to evolve were the destructive sequences, they could not be passed to the offspring. Were the rectifying processes to evolve first, they would not be functional if the destructive processes had not done their work. It is not reasonable to expect (at a high cost of material and energy) a cell/organism would randomly develop one of these complex rectifying processes with the expectant hope that a corresponding destructive process would someday emerge. Natural selection has no means of anticipating or expecting future outcomes. For the message to the IMF to be destroyed, there had to be a plan; a self-destruct mechanism had to be placed into the tape player by design. Similarly, the forethought needed to plan out such complex mechanisms for destructing and reconstructing in living systems could only reasonably come about through intelligent agency.

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