Ugh I'm back on my computer that doesn't let me quote which is a huge pain but to address a few things using @Chillman 's post as a jumping off point.
Ace is right about Teinshinhan. However a few caveats-
-Daizenshuu 7 says Tein is descended from aliens that ended up on earth a long time ago. How long they've been on earth and how much they have/haven't interbred with humans is left up in the air.
-The line about Tein's lineage is one of the very few pieces of new information in the Daizenshuus that's isn't directly from Toriyama or an editor or similar(through an interview or the like). As such people have questioned the validity of that factoid as long as Daizenshuu 7 has been around. Personally I always believe the guidebooks in the absence of direct contradiction of other materials (which the are a few cases of) and I've often found people only seem to discount that particular fact for self-serving reasons, but it's something to keep in mind.
-It's also entirely possible that Tein is both an alien and got the third eye through meditation. After all, Supersaijin is a genetic trait for Saijins but they need to do something to actually unlock it.
-This is more of an interesting aside than anything, but it's very rare for any official materials in Japan to refer to any character as "human". I think there's a few occasions were the term is used, especially in reference to the androids, but they almost always use the term earthlings instead, which also includes people like Tien, Oolong, Puar, Popo, Pilaf ect..
Yes the Ginyu fight on Kai's planet is filler and what they did or didn't accomplish on King Kai's planet is left undisclosed.
Roshi is mortal but him and his sister live freakn' forever, Baba is somewhere around 600 iirc., Roshi is about 350. No official explanation why, probably something to do with the fact that Roshi is a Sen'nin (a type of sage often said to have transcended age through enlightenment and whatnot) and Baba is magic n' stuff. There's a throwaway line about Roshi drinking from the fountain of youth but that's dub only. He says during the Piccolo arc that he drink an elixir of immortality, then right afterwards admits that that was a lie, and then he dies.
Only thing I can contribute about the androids at this point is that in the Dragonball Full Color: Artificial Humans and Cell arc Volume #6 interview, Toriyama explicitly states that Android 17 and 18 can become stronger by training, since they're modified humans.