>>Sparrows and bats have a common ancestor but it is improbable that it had wings.
Isn't this a required truth of evolution (not necessarily these animals, but the concept) - that humans and centipedes (or sharks, or dogs, or pigeons, or mushrooms, etc.) all have a common ancestor if you could trace evolution with perfect accuracy back to the beginning of time? Sparrows and bats, being birds and mammals, respectively, would likely have a common ancestor with less in common between the two than sparrows and pigeons or bats and ferrets, correct?
I'm no expert in evolutionary science beyond the basics, so correct me if I am wrong. I read your comment to suggest that evolution does not require any sort of "missing link," which I don't know enough to talk about.
> Isn't this a required truth of evolution (not necessarily these animals, but the concept) - that humans and centipedes (or sharks, or dogs, or pigeons, or mushrooms, etc.) all have a common ancestor if you could trace evolution with perfect accuracy back to the beginning of time?
No, its not a "required truth of evolution". Evolution works just fine if you have life arising independently in multiple places.
Universal common descent was among the hypotheses Darwin proposed in The Origin of Species, but its certainly been challenged many times without the basics of evolution being challenged; I think it is part of the current scientific consensus based on the available evidence, but its not at all necessary to evolution.
Thanks, that makes sense to me, but it has never been presented to me like that. It's similar to spoken languages evolution, then, correct? In that many languages developed very similar basic rules independently? I don't have a lot of experience beyond high school evolution lessons (which present the common ancestor as a necessary piece of the puzzle), but I took some nature of language classes in college and found that very interesting.
My point is that morphology has proven to be a poor way to determine evolutionary relationships in light of modern genetic sequencing and beyond extant species or those of the recent (evolutionary) past it becomes increasingly suspect. The most recent common ancestor of humans and whales probably looked shrew like.
By the time one goes back half a billion years, morphological similarities become like snakes and earthworms - likely to arise independently based on environmental factors.
Let me put it this way: The elephant bird of Madagascar and homo sapiens evolved bipedialism as their primary form of locomotion as an adaptation to their environment. Until historical times, neither was extinct. Imagine our evolutionary successors claiming that the elephant bird is the missing link between birds and bipedal mammals of the world 500 million years from now.
As I understand it, those sort of relationships rely on the reasonableness of human-defined taxonomy.
For instance, if we referred to eels as "snakes" then they would have less in common with other snakes than they would with fish (I believe they are closely related to fish anyway, I might be wrong there).
Also, there are also some relationships that many might find surprising. For instance, most people know that birds and reptiles are fairly closely related, but the fact that crocodilians (alligators, crocodiles, etc) specifically are the closest living relatives to birds might be surprising. Personally I would have guessed some sort of more nimble reptile, lizards perhaps.
Isn't this a required truth of evolution (not necessarily these animals, but the concept) - that humans and centipedes (or sharks, or dogs, or pigeons, or mushrooms, etc.) all have a common ancestor if you could trace evolution with perfect accuracy back to the beginning of time? Sparrows and bats, being birds and mammals, respectively, would likely have a common ancestor with less in common between the two than sparrows and pigeons or bats and ferrets, correct?
I'm no expert in evolutionary science beyond the basics, so correct me if I am wrong. I read your comment to suggest that evolution does not require any sort of "missing link," which I don't know enough to talk about.