...and many other planets were seeded later and evolved life based on that one type of DNA. But that doesn't mean that intelligent creatures that evolved on any of those planets would necessarily be humanoid in appearance. The naked ape design was an accident peculiar to us. On another world it might be insectoid, or octopus-like, or something very different in appearance from us, or from any earth creature.

We know all life on earth evolved from one microorganism, because we all share the exact same DNA. But there are many billions of different types of organisms on earth now, from turnips to tuna. On our planet, tool making intelligence evolved in mammals, on another it might have evolved in something totally different. (I was going to say birds, or dinosaurs, until I realized another planet might have our DNA and not have evolved birds or reptiles of any sort.)

Or maybe, on our sister planet, intelligence didn't evolve at all.

As far as we know, tool-making intelligence is not necessarily a survival trait. It's only evolved in the last million years of a 3500 million year history of life. It hasn't been around as long as say, the eyeball, or the feather, or hemoglobin, it hasn't proven itself yet.

We can arrange every living thing on earth into an evolutionary family tree that clearly didn't have anything "grafted" on to it from outside. At every critter branch or tip, we can find ancestors to it in the fossil record. Every creature and plant on earth evolved from the same creature, at the root of the tree. It is possible different types of life evolved here in the past, or were introduced from outside, but none have survived to the present day. Any competing biochemistries, foreign or domestic, lost the evolutionary contest long ago.

Nope, this is our world. We either evolved from dead matter here, or we were seeded from somewhere else. But now it is ours, and totally ours. We earned it, and we haven't shared it with anyone else. And if we have genetic cousins living elsewhere, we'll have to check their chemistry in the lab to determine that, because they will have evolved totally differently than us and they won't look like us at all, even if they are chemically similar (have the same proteins, etc).

However, at least some of them will probably be edible. And vice-versa. And if they came here, or we went there, survival might just be possible.