Were Adam and Eve the only people in the world?

First of all, English is not my main language so sorry if I'm not explaining my self clearly.

So my question is were Adam and Eve the only people in the world when they had been created? I've seen many theories on how they populated the world from so few people, (That Cain and Abel were born with twin sisters, and reality was different at the time...) but the most interesting one that I've read is that Adam and Eve were the only ones in the Garden of Eden, but many other people existed on Earth, too. And the Torah didn't mention it because.. well like many other stuff it doesn't mention - it doesn't concern to us.

I'd like to see what is your stand on that matter, and maybe learn something new. P: