Pawn Movement

Does anyone know the history or logic behind the discrepancy between the pawn's normal movement and its movement when capturing?  Kinda curious, and Wiki doesn't really help.

I don't know if there is any merit to this, but I've always thought of it this way:

The pawn is a soldier moving forward with a shield... to strike with his sword or spear, he has to swing around the shield, or in the case of chess, diagonally.  This analogy could apply to the Knight as well but the concept extends a square as the Knight on horseback has greater range with a lance.

On another note, I'd argue the pawn's value has a great deal to do with its position on the board and the stage of the game.  It always has the potential to be greater than it started and so I wouldn't categorize it as less valuable.

People have told me the same thing regarding the idea that pawns are holding shields.  That sounds reasonable enough, though I'd still like to know if there's any historical backing behind this concept.

And you're right that, depending on the position, a pawn isn't necessarily the least valuable.  That short spiel in the beginning was only meant to provide some intro to my opening post.  Regardless, I'll make the necessary changes to make the passage more accurate.

Thanks for the reply.

I really didn't want the value and/or power of the pawn to be the focus of this thread, so I'll just omit that from the original post.