Phalanx warfare: Closing of the ranks

[Paul Bardunias]

So if ranks three and beyond in a hoplite phalanx didn't use spears to fight the enemy in the clash, besides replacing casualties among the promachoi, I think the big question is, what role did they serve? Why add depth if their spears are useless? Why not just take the extra bodies and extend the line outwards to attempt to encircle the enemy? Or add multiple lines, like the Romans, so if the first phalanx breaks the other can take up the fight?

To a point, depth has a morale function,  and that along with replacement can explain shallow ranks.  T me deep ranks- 12,16, 25, 50+ can only be explained by the threat of othismos.

If you angle the spear down between strikes, and hold it near the rear, you will not hit the guy behind you.