...Who knows, perhaps the two are the same species after all? One or both might just have decided to toy with their phenotypes a bit during their supposedly very long histories. And with their genotypes, as "Second Skin" et al. make it clear that there is an easily detectable difference. But that latter fact should already make creation of offspring difficult, even if it happens that Cardassians, too, have reproductive systems and processes that make the mother sneeze a lot during pregnancy...
As regards the abundance of humanoid life, we might just as well figure in the likelihood that the galaxy is full of Earth-like worlds. After five billion years of sapient life, it would be highly unlikely for the planets to be "natural" any more: all would have been mined, exploited and, whenever possible, terraformed. That is, originally several civilizations would do their own 'forming to their own specs. Soon enough, one would become dominant, and re'form the worlds of the others. And any civilization coming afterwards would emerge from a terraformed planet and find the skies full of the same sort, making it easy for the civilization to expand and then add to the number of terraformed worlds. Competing civilizations, preferring other environments, would be at a massive disadvantage and would wither and die.
That doesn't yet explain why all the civilizations feature bipeds much like us. One needs something like "The Chase" for that, and this requires technologies beyond our current understanding (whereas making all the planets in Milky Way duplicate Earths does not).
Timo Saloniemi
As regards the abundance of humanoid life, we might just as well figure in the likelihood that the galaxy is full of Earth-like worlds. After five billion years of sapient life, it would be highly unlikely for the planets to be "natural" any more: all would have been mined, exploited and, whenever possible, terraformed. That is, originally several civilizations would do their own 'forming to their own specs. Soon enough, one would become dominant, and re'form the worlds of the others. And any civilization coming afterwards would emerge from a terraformed planet and find the skies full of the same sort, making it easy for the civilization to expand and then add to the number of terraformed worlds. Competing civilizations, preferring other environments, would be at a massive disadvantage and would wither and die.
That doesn't yet explain why all the civilizations feature bipeds much like us. One needs something like "The Chase" for that, and this requires technologies beyond our current understanding (whereas making all the planets in Milky Way duplicate Earths does not).
Timo Saloniemi