I literally just watched Collective two minutes ago and it didn't occur to me to ask that question.
Um. They found the baby's homeworld between episodes! Yeah, that's it.
But that is the perfect answer to everything!
It's the duct tape of continuity.
My biggest question: If Earth is a unified planet, why is 80% of the population white?
The Eugenics wars were much
nastier than they have led us to believe.