Stargate

My belief is that the ending of SGU was going to be that the pattern in the background radiation was residual energy from a Dakara Superweapon style device that seeded life across the whole universe (or at least the local cluster).

If you are happy to stretch your suspension of disbelief you can also consider that the humanoid form seems to be a common convergence point of evolution. Similar to crabs: crabs have evolved potentially dozens of times independently on Earth in real life. So if the Ancients seeded life on Earth to mimic their own evolutionary starting point, then maybe Earth naturally got up to Neanderthals and other species, which eventually were cross bred or manipulated to result in modern day man. This would be supported by the fact that a decent amount of humans have the Ancient gene, or are compatible with the retrovirus. Perhaps the Ancients didn't have things like gorillas or elephants back home, but things quite similar. I'll bet they definitely had crabs though.