Prepare to have your mind blown. The answer is… never.
That’s right! The first human was never born. There was no first human. And it gets even more interesting. There will never be a last human. In fact, it is safe to say that there is no such thing as human. “Humans”, as we know them, have no independent existence.
What does exist however, is a relative existence. It is a limited, in-between kind of being — something that started happening when we began to speak, is happening right now, and will continue to happen until evolution turns us into something that can no longer be defined using the word “human”.
And that’s all “human” actually is — a word. It has no more meaning than what we have assigned to it. It is a very specific word with a very specific usage that has currency among members of a particular species who use spoken language to communicate with each other. They think they are something. Some of them even think they are everything — the pinnacle of creation, the very height of perfection, the most sublime expression of the universe’s will. It’s the funniest thing ever!