Is there life on other planets? Frankly, the only answer I can give is "we can't know". But here are some points that we do know:
- All humans are descended from Adam and Eve. The New Testament is quite clear on this: Adam is the patriarch of our earthly race, just as Jesus is of the heavenly.
- The entire universe was affected by the sin of humanity. Even inanimate objects are affected.
- God is just, and will not punish people who have not sinned. It's hard to find a citation for this, because there are no such people; but we know that God is righteous, and detests injustice, and if He defends someone described as "innocent" in legal terms (who is still a sinner), how much more someone who has actually never sinned!
So our universe can't have anyone in it who was capable of deciding to not sin (apart from Jesus, who willingly and knowingly took on all the consequences of sin). That means that there cannot be any sentient humans who are not descended from Adam, nor any other sentient races. We're not going to send a spaceship out and discover alien races that look almost identical to humans except for some facial differences. What we'll find will either be nothing at all, or non-sentient life (plants and such), or actual humans whose ancestry traces back (even if they don't know it) to Adam and Eve, and who are themselves sinners in need of a Saviour.
(Aside: How could there possibly be humans on other planets? If we don't have space travel technology now, and aliens didn't give it to us, how could the ancients have travelled to other stars/planets? Well, that question assumes we're constantly getting better, which isn't exactly a proven fact. There are plenty of periods of history we know little about, and if someone hit on a means of using quantum tunnelling to flee from the oppressive Roman empire, or to find a new life away from the threat of Babylon, or whatever, then it's entirely possible the skills and technology departed with the small group of colonists who used it. This differs only in scale from the questions of "How did the so-and-so people get to such-and-such island?", and it's quite reasonable to believe that technology for ocean-going ships was discovered more than once in history. Personally, I would suspect that there aren't any humans on other planets, but scientifically and philosophically, I can't rule out the possibility. Which would mean that the Great Commission applies to space travel... this could be fun! End aside.)
The genealogies in the Bible never go beyond Adam (other than to conclude "the son of God"), and early humans can be identified by their generational positions relative to Adam. The entire Bible assumes that Adam is the beginning of the human race. We are told that Adam is not the son of some sort of "proto-human" or non-sentient primate, but was formed from dust and breathed into. God didn't take the product of millenia of evolutionary development and say "Okay, this one's good enough to be called human". He made people in His likeness. We, in some way, look like "little God figurines". (Or at least, we did when we were perfect. Now we're little damaged figurines, but I suspect we're still somehow recognizable.) And of course, we're genuinely capable of thought and action, unlike the figurines that we make ourselves, and we all have our own identities. In so many ways, humans are special; we're not just "really smart animals", and we're certainly a lot more than bags of chemicals and electricity. We are God's representatives here on earth.
Random thought to leave you with: Does that mean the church is an embassy? Or is it more like a High Commission?