I remember a joke being told to me quite some time ago. It goes like this: There were two gentlemen sitting next to each other, one an Englishman and the other being a Hungarian, English being a second language to him. The Hungarian, wanting to know the time, asks the Englishman, in the best English he could muster, "What is time?" and the Englishman answers "That's a very difficult question to answer."

Anyway...I want to offer a simple theory on how the notion of time might have dawned on humans at the earliest stages of our evolution.

A discussion on space seems necessary first. Imagine X, an early human, trekking through the African savannah. The savannah are vast stretches of grassland with a few scaterred trees here and there. So, X, walks and comes across a tree, no fruits but still a tree. Then he continues along for another mile or so and then he encounters another tree - this one has fruits. In essence, he's met two trees and assuming he knew how to count up to two - it's said that early math began with the ability to count up to two - and assuming he was capable of ordinal math [the ability to order, sequence, as like first, second, etc.], X would've ordered the trees as such: first tree, no fruits; second tree, fruits. This ordering, this sequencing, must be contextualized, it requires a...dimension. The dimension in which the trees are first and second is space.

Noticing the fruits on the second tree, X decides to camp at the spot. The fruits look green and his experience tells him they can't be eaten as of yet - they won't taste good. He has supplies that'll last him a few days. A few days go by, X is still camping next to the tree, but the fruits have now taken on a reddish tone. Ah! X thinks, they're good to eat and he does with relish. Now, to X, something happened to the fruits, expressible as: first, it was green; second, it became red. In essence, there's an order, a sequence, as it were. However, the tree and the fruits haven't moved at all - they were there, they're still where they were. Ergo, X concludes, the sequence/order has nothing to do with space. In what context is the order/sequence of the fruits' condition occuring? In other words, in which dimension is the order/sequence of the ripening of the fruits taking place? Time. X has now developed the concept of time.