A linguistic question (looking mainly at you thnidu, but there are other folks who might know, too)

Elsejournal, a couple days ago, someone wrote a post which quoted Bishop John Shelby Spong: "The verb 'to be' is the key verb in every human language. We use it to describe that which is of our very essence."

The post was, and is, a lovely meditation on the nature of coming out, and the reactions to National Coming Out Day, but I objected to that quote, saying that plenty of languages lack a verb "to be".

So it started me wondering: do languages with an explicit verb "to be" fall into any specific clusters? Do some language families have them, and others lack them, or is it more scattershot?