It depends on the depth of convergent evolution.
First, let's limit the discussion to earth-like planets, with water seas and yellow suns. On Earth, there has been a huge range of diversity in body plans, limbs, organs. Over hundreds of millions of years, some forms have disappeared, perhaps outcompeted by other forms that came to predominate.
But DNA and RNA are pretty universal in Earth life-- plants, animals, fungi, etc. Must be because, once they evolved, they worked better than anything else. If this is true on Earth, it might also be true on all earthlike planets.
I read recently that we might be able to spot life on distant worlds by detecting chlorophyll in the atmosphere. Chlorophyll is a lot simpler molecule than DNA, but even so, its presence would indicate a high level of convergent evolution.
We are not justified in assuming that life is infinitely variable. Some forms work, and others don't. The ones that work best will come to predominate.
Could some computer whiz design an alternative to DNA that works better, or at least just as well?
Could evolution switch out a potassium for a calcium atom? Or a silicon for a carbon? What if it spiraled the other direction? Would that still be DNA?
Thus I believe that worlds with similar environments will evolve very similar lifeforms.
This goes farther than DNA. I think there's a good chance that earthlike worlds will evolve tall, bipedal, big-brained, two-eyed, two-handed beings.
It depends on the depth of convergent evolution.First, let's limit the discussion to earth-like planets, with water seas and yellow suns. On Earth, there has been a huge range of diversity in body plans, limbs, organs. Over hundreds of millions of years, some forms have disappeared, perhaps outcompeted by other forms that came to predominate. But DNA and RNA are pretty universal in Earth life-- plants, animals, fungi, etc. Must be because, once they evolved, they worked better than anything else. If this is true on Earth, it might also be true on all earthlike planets.I read recently that we might be able to spot life on distant worlds by detecting chlorophyll in the atmosphere. Chlorophyll is a lot simpler molecule than DNA, but even so, its presence would indicate a high level of convergent evolution. We are not justified in assuming that life is infinitely variable. Some forms work, and others don't. The ones that work best will come to predominate. Could some computer whiz design an alternative to DNA that works better, or at least just as well? Could evolution switch out a potassium for a calcium atom? Or a silicon for a carbon? What if it spiraled the other direction? Would that still be DNA? Thus I believe that worlds with similar environments will evolve very similar lifeforms. This goes farther than DNA. I think there's a good chance that earthlike worlds will evolve tall, bipedal, big-brained, two-eyed, two-handed beings.
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