Two things-
First, chlorine is much rarer than oxygen. Any world where it is common enough to be the basis of the biochemistry has almost certainly been tampered with by an elder race at the dawn of time.
The plant equivalents would turn Cl- into Cl2, just as earthly plants produce oxygen by splitting water, but the energy demands for chlorine are significantly higher. The chlorine plants would need more light than ours, preferably blue or soft ultraviolet. Their planets would typically be sunny, not venus-like, and circle hotter suns than ours.
Second, new species can form very rapidly - the cichilid radiation in the East African lakes took under 100,000 years, maybe as little as ten thousand - but only when a species moves into empty niches. Humans occupy the cognitive niche; with only minor exceptions, rather than evolving new physical adaptations to suit a new lifestyle, we modify our cultural tool kit.
E.g, rather than evolving teeth well adapted to eating meet or grains, like cats or horses, we cook our food, leaving our teeth generalised. Biological evolution among humans is mostly restricted to solving problems our technology historically could not handle, such as disease resistance.
Furthermore, recently seperated species only evolve interspecies mating barriers when they are still in close proximity. If mating with the other species isn't an option, there's no need to evolve mechanisms that would prevent it.
Adapting to alien ecologies won't inadvertently create such barriers either. It's a situation like lactose intolerance on Earth - the necessary adaptaions don't compromise hybrid viability. A barrier would have to be created intentionally, not merely as a byproduct of other genetic alterations, but as an end in itself - unless the precursors are using genetic engineering on such a scale that they could as easily have started with gibbons and produced the same result.
Thus, I'd expect that, while there would doubtless be cultural barriers to intermarriage, anyone with a taste for the exotic would have little difficulty conceiving an hybrid child.
First, chlorine is much rarer than oxygen. Any world where it is common enough to be the basis of the biochemistry has almost certainly been tampered with by an elder race at the dawn of time.
The plant equivalents would turn Cl- into Cl2, just as earthly plants produce oxygen by splitting water, but the energy demands for chlorine are significantly higher. The chlorine plants would need more light than ours, preferably blue or soft ultraviolet. Their planets would typically be sunny, not venus-like, and circle hotter suns than ours.
Second, new species can form very rapidly - the cichilid radiation in the East African lakes took under 100,000 years, maybe as little as ten thousand - but only when a species moves into empty niches. Humans occupy the cognitive niche; with only minor exceptions, rather than evolving new physical adaptations to suit a new lifestyle, we modify our cultural tool kit.
E.g, rather than evolving teeth well adapted to eating meet or grains, like cats or horses, we cook our food, leaving our teeth generalised. Biological evolution among humans is mostly restricted to solving problems our technology historically could not handle, such as disease resistance.
Furthermore, recently seperated species only evolve interspecies mating barriers when they are still in close proximity. If mating with the other species isn't an option, there's no need to evolve mechanisms that would prevent it.
Adapting to alien ecologies won't inadvertently create such barriers either. It's a situation like lactose intolerance on Earth - the necessary adaptaions don't compromise hybrid viability. A barrier would have to be created intentionally, not merely as a byproduct of other genetic alterations, but as an end in itself - unless the precursors are using genetic engineering on such a scale that they could as easily have started with gibbons and produced the same result.
Thus, I'd expect that, while there would doubtless be cultural barriers to intermarriage, anyone with a taste for the exotic would have little difficulty conceiving an hybrid child.