I suppose, depending on how one defines a human being, there had to have been a first pair of us, somewhere.
Nope.
There never was a "first human", just like there never was a "first spanish speaker".
Or I suppose a first one of us with some dominant genetic mutation that defined him/her as a human being apart from his/her's parents, and that then spread through procreation.
Nope. No non-human has ever given birth to a human. Or more generically: no individual was ever born which didn't belong to the same species as its direct parents.
In the same way, no latin speaking parents have ever raised a spanish speaking child.
Instead, every child grew up speaking the same language as its parents / peers.
The thing is, though, that it's a collection of traits that define us as human beings, and those will likely have developed separately over time. So that there would not likely have been any one individual source to name "Adam" or "Eve".
Indeed. Evolution is a
gradual process. No one mutation defines a species. No individual defines a species.
And while mutations are introduced through individuals, it's
populations that evolve.
Just like no single person came up with spanish or italian.
Instead, it's a slow and gradual process of accumulation of micro-changes which gradually spread in the population. So every new generation is 99.999% like the previous one.
After many generations though, that 0.001% difference adds up through accumulation.
The difference between generation 1 and 2 is almost nihil.
But the difference between generation 1 and 2000 is potentially very large.