Why Do Speak So Many Languages*?
* Inspired by a recent Arun Post.
As has been well documented, human languages are all underpinned by the same neural substrate - the same language instincts - and are largely equivalent in expressive power, at least in the relevant contexts. So why, having invented language, would we go crazy by inventing mutually incomprehensible variants for every group of a few hundred speakers (before farming and the rise of large civilizations).
Well, it could be purely accidental, but I suspect a darker motive. Readers of the Hebrew Bible or of Steven Pinker's The Language Instinct might recall the story of the Shibboleth. Having won a certain battle, the Lord's elect had to sort out their side from those that God had selected for slaughter.
Gilead then cut Ephraim off from the fords of the Jordan, and whenever Ephraimite fugitives said, 'Let me cross,' the men of Gilead would ask, 'Are you an Ephraimite?' If he said, 'No,' they then said, 'Very well, say "Shibboleth" (שבלת).' If anyone said, "Sibboleth" (סבלת), because he could not pronounce it, then they would seize him and kill him by the fords of the Jordan. Forty-two thousand Ephraimites fell on this occasion.
—Judges 12:5-6, NJB
There are a zillion of these little cultural touchstones to distinguish one group from another: tattoos, Gucci purses, dietary restrictions, modes of dress or adornment, all with the primary purpose of partitioning people into groups. Into those we spare, and those we slaughter, either literally or figuratively.
Celebrate diversity! It's how we tell whom is the enemy.