Inbreeding destroys human genes due to the natural need for diversity.
Maybe those aliens forgot that. Whoops, we created planet idiot.
That wasn't the only "pod". An agent said something about having tracked 41 (?). There were probably enough to seed the planet again.
shareUnless, like regrowing kidneys and legs, the alien objects perfected each person's DNA, replacing any genetic deficiencies. Genetic tendencies for diabetes, down's syndrome, obesity, and all diseases related to genetic makeup... gone. Remember how the scientists' observations of the alien object containing human DNA?
Studies indicate a population of about 40,000 people would be needed for healthy diversity. That's 40,000 copies of our defective DNA. I think as time goes on, our DNA becomes worse with each generation as people with defective DNA live long enough to reproduce, 'thanks' to modern medicine.
I thought that too at the end but then I remembered earlier on one of the scientists saying that even the piece of the alien pod they had analyzed contained the DNA of multiple species. It's not too much a stretch then to assume that the pod would be able to add in the human genetic diversity that, you're right, would be needed.
shareSo at this point there are two reasons pointed out that you're just wrong about this. First that there wasn't just one pod and second that they contain dna information for humans as well as other forms of life.
But none of that is really essential. This is a rework of the Noah story. Realism isn't the thing.