If humans were transplanted to a different Earth-like world that they didn't evolve on, how would they deduce how they came about?

Question

I have a world where prehistoric humans were kidnapped and transported to another world. This other world is Earth-like, with mammals (also transported from Earth then later diversifying into other species), as well as some species that evolved on the planet itself. Apes were never transported to this world.

Those beings who transplanted the humans ended up having other concerns and long ago left the world alone. Humans ended up developing technology and science just like we have, and have reached a level of technology similar to our own.

However, their ability to deduce evolution is going to be made harder by the fact that there are so many missing links. Mammals from earth are very different from the native species of the planet they are on, and humans are fairly different from those mammals that were transplanted to the planet. There are also very few mammals, as only those deemed interesting/useful were transplanted, which leaves explaining their origin difficult. How would humans deduce what has happened?

I'm interested actually in two time periods. What would humans at roughly the technology level of Darwin, or slightly after, who didn't have access to carbon dating or as detailed a fossil record deduce, and what would 'modern' humans with better technology deduce?

There are no fossil records of the aliens who transported humans. Furthermore, humans were transplanted at a time of high geological turbulence, which may be used to explain the difficulty of finding fossils from that time.

I know that religion and intelligent design will come up, and likely be even more commonly believed than in our world, but I'm curious what scientists and atheists would deduce from the fossil record.

Answer 1

Once they get serious about biology, it should be pretty easy to see that there are two categories of life form. You don't need to look at the history: there will be plenty of anatomical and biochemical markers to indicate it. Genetics will make it even clearer, once that's invented.

(This assumes the underlying biochemistry is very similar. Without that, species will be stuck eating species with the same native planet, and the exact lists will be well known in antiquity.)

Once the paleontologists get involved, it'll get weirder. One category of life has a complete fossil record and an unambiguous evolutionary history. The other category has no fossils at all until extremely recently. Furthermore, the appearance of the new category triggered mass extinctions and ecological catastrophe, as successful invasive species inevitably do.

This will still leave a question: did the Category II life evolve elsewhere and travel here somehow, or did it simply pop into existence? Category II life does show signs of being evolved and not designed, but it's not enough to say for sure. Genetics will be strong evidence for the travel theory. Occam's Razor will suggest spontaneous generation until physics or astronomy gets really good.

Once they have both of those, they'll probably deduce the truth.

Answer 2

People on your planet would have a problem in attempting to explain their origins. Much of the evidence that is used to support evolution would be missing such as the fossil record and the vast range of different animals and planets we have on Earth and presumably any clues from geobiology and animal distribution. I suspect that the discovery of evolution would be greatly delayed and distorted. At the time of Darwin there probably would not be sufficient evidence to support the theory.

However with some care and by the time of today’s technology it should become clear from molecular biology that all of the mammals were closely related due to the similarity in their biochemistry and that all of the alien species were similarly closely related to each other, but in addition were also, well, very alien indeed. In fact they would not share any genes and probably not even DNA. Their biochemistry would be very different. Both types of organism would probably be mutually toxic to each other due to the separate biogenesis and billions of years or refining totally different biochemistries.

What would modern science make of this? It might be able to predict two different biogenesis events and relationships within the two different biochemical “kingdoms” but with so many missing species and dislocated parts of the story it might remain a continuous theory with insufficient evidence.

Answer 3

With Intelligent Design on Earth, much of it is about religion(and simple egotism) causing people to believe that humans are special. You'd see the same idea on this world but with much more evidence, because the overwhelming majority of the fossil record only applies to native species. It's likely that the above factors will lead to the belief that humans really are special.

With two unrelated chains(Earth animals and natives), it will eventually be obvious that not just humanity but that all Earth life is not unique to this world. It would thus not be as obvious that humans aren't as special as we want to believe. You could thus have something resembling atheism without being a Flat Earth Atheist, as TV tropes would put it. It would be about believing that humans were not the only ones that aren't native and that this doesn't jive with religious beliefs, unless those beliefs are based on the real origin.

In Darwin's time, you probably wouldn't see the theory of evolution form, because life on this world did not evolve naturally. It would probably take until the 20th century for this to be possible. If nothing else genetics will absolutely be different, and comparing the genome of Earth animals and native species will show a clear difference, while comparing humans and other life from Earth will show similarities.

I should also note that an extraterrestrial origin for life is actually a hypothesis made on this Earth. Not a well supported one, but it has been made. So there is no reason to assume that it wouldn't be made in this case eventually.

Answer 4

(Regardless of what you believe in this Earth...)

You already answered (part of) your question; they'll believe in Intelligent Design¹. Genuine science does not a priori reject extraordinary explanations just because they are extraordinary. True scientists won't reject "IDESOT", especially since it happens to be correct.

What your "athiests" will do is another matter. "Atheism" (both in our world and in your context) is based on the a priori rejection of supernatural causes (which is, by definition, unscientific). Human nature being what it is, you will almost certainly have IDESOT deniers, just like we have crackpots that still insist the Earth is flat rather than (roughly) spherical. As to what they'll offer as an alternative theory... hard to say. We can say, however, that they will find a way to explain away any evidence contrary to their pet theory.

(¹ They might not call it "Intelligent Design", since technically it isn't "design". Maybe something like "Intelligence-Directed Extra-Solar Origination Theory".)