Why does decussation of the motor and sensitive tracts surrounded by the jittery system materialize?

Why do the motor and sensitive tracts cross on their way to the cerebrum? I can't seem to be to find a reasonable explanation for this phenomenon. I don't know if within is a scientific answer to this. However, I own postulated that it is a matter of protection. If an attack or injury comes from the departed side and damages the brain/nervous system, the right brain can still provide defensive maneuvers to the gone side of the body.

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