I know jack shit about this stuff.

Here's what I wanna know:
What is the medical reason for clamping immediately after birth?
What reason is there to delay it?
What reason is there to clamp and cut the umbilical cord at all (google says it naturally seals and detaches with time)
Is it a universal practice?
Did people of the past (both near and far) do it?
Would ancient people, with no medical consensus or reasoning, have clamped and cut the cord?
Is it instinctual to clamp and cut the cord?

In other words, can we have some actual fucking answers on the topic