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Human evolution has a reasonably complete fossil record pointing to the fact that we and apes evolved from a common ancestor within the last 10 million years or so. But I want a world where it could be reasonably assumed that humans were simply transplanted here, perhaps created or moved here by some aliens. In order for this to happen, there would have to be no fossil record that directly links us to an evolutionary ancestor. Other than the necessary changes, I want this alternate world to be as Earth-like as as possible.

What is the smallest change that would remove any evidence of human evolution from an ape-like ancestor?

In order for this to succeed, there can be some traces of recent human evolution (such as Neanderthals, perhaps) and some traces of earlier apes and primates, but a large enough gap in time leaving 'doubt' as to the origin of humanity.

For the purposes of this question, ignore any scientific ways of connecting humans to apes, other than fossil record. For example, ignore the similarity of human and ape DNA. Any fossil evidence must be very unlikely to be found by the time humanity has progressed to a technology level equivalent to today's.

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    $\begingroup$ You would necessarily need to replace human DNA with a thoroughly rewritten version; fossils are no longer the primary means of tracing the ancestry of living creatures, and it has not been for several decades now. And I mean a thoroughly rewritten version. Our DNA shows our common ancestry with (in increasing order of distance) the other great apes, lesser apes, monkeys, rats and mice and rabbits, wolves and cats, birds, lizards, frogs, fish, squid, mushrooms, oak trees, ferns, mosses, algae, yeast and bacteria. And don't forget embriology... $\endgroup$ – AlexP Jan 7 '18 at 21:17
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    $\begingroup$ @AlexP I did say to ignore the DNA connection in the answer. I'm only talking fossils here. $\endgroup$ – kingledion Jan 7 '18 at 22:09
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    $\begingroup$ Your question is confusing. If humans didn't evolve on Earth, then we won't be genetically similar to anything else on Earth. There also wouldn'd be any of our ancestors in the Olduvai Gorge, etc. $\endgroup$ – RonJohn Jan 8 '18 at 15:13
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    $\begingroup$ Define "viable". (There's a boatload of people now who don't believe that humans -- or any other creature -- evolved.) $\endgroup$ – RonJohn Jan 8 '18 at 16:55
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    $\begingroup$ I don't believe Darwin relied on fossil evidence. Examination of the physiology of extant animals was plenty evidence to deduce the human->ape->monkey->primate->mammal connections. If no fossils ever existed, we might know about dinosaurs, but we'd know the connection between humans and other animals. $\endgroup$ – user3294068 Jan 8 '18 at 17:43

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Flood. We are really bad at finding evidence underwater. If humans had evolved in a valley such as what is now the Mediterranean Sea, complete humanoid fossils would be very difficult to find.

https://en.m.wikipedia.org/wiki/Zanclean_flood

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  • $\begingroup$ Picture this two mile deep trench, floored with with few hundred feet of salt. I challenge your humans to survive in Death Valley first. And good luck evolving. $\endgroup$ – user58697 Jan 8 '18 at 6:16
  • $\begingroup$ The question specified "earth-like," not earth. Salinity is not relevant, as saline-tolerant organisms are possible, as are freshwater rivers that empty into saline lakes. I also picture a more fun flood like this one: $\endgroup$ – Lurker Larry Jan 8 '18 at 7:02
  • $\begingroup$ en.m.wikipedia.org/wiki/Bonneville_flood $\endgroup$ – Lurker Larry Jan 8 '18 at 7:06
  • $\begingroup$ Salinity wouldn't be the biggest problem, think more like "theoretical temperature maxima would have been around 80 °C (176 °F) at the lowest depths of the dry abyssal plain permitting little life other than extremophiles." (en.m.wikipedia.org/wiki/Messinian_salinity_crisis) Happy evolving! $\endgroup$ – Erwin Bolwidt Jan 8 '18 at 15:33
  • $\begingroup$ That would be a plus-one for hairless apes then, right? Why must one live at the bottom of a canyon? Instead of hundreds of feet deep, how about just fifty? Bottom line, evolve humanoids somewhere and then drown said location. Also, do you not consider a range of habitats reason to expect more species, not fewer? $\endgroup$ – Lurker Larry Jan 9 '18 at 1:06
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Humanity evolved in the rainforest, not the savanna

The reason that there exists such evidence of human evolution as there is, is that humans occupied a broad swathe of savanna stretching from Ethiopia to South Africa for most of the time between 4 and 2 million years ago. During this time, human's various ancestors (Australopithecus and Homo habilis, mostly) was not found anywhere else.

In addition, there is very little evidence connecting Australopithecus to anything before it; there is already a lacunae in the fossil record between about 5 and 7 mya.

Rainforests do not preserve fossils well; the action of tree roots, fungus and plentiful water tend to ensure that any organic matter laid down is destroyed quickly.

Therefore, if humanity's known (to us) fossil ancestors before Homo erectus were rain-forest dwelling creatures, then there would likely be no fossil remains of them. Thus, Homo erectus fossils would be found all over the world starting about 1.8 million years ago, yet there would be no fossil evidence linking Homo to any earlier creatures; all earlier fossils could be reasonably interpreted to be in the lineage of chimpanzees, and not man.

And thus, the number of people who believed that humanity was placed on Earth by aliens would be substantially increased :)

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  • $\begingroup$ Not just rainforest - any forest that can catch fire (lightning strike) will tend to convert bones to ash unless the ancestors buried their dead. $\endgroup$ – Alan Campbell Jan 8 '18 at 6:42
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    $\begingroup$ Rainforests do not preserve fossils well; the action of tree roots, fungus and plentiful water tend to ensure that any organic matter laid down is destroyed quickly. Well, not so much destroyed as... repurposed $\endgroup$ – xDaizu Jan 8 '18 at 10:20
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    $\begingroup$ The biggest problem with this: It would be much more unlikely for humans to evolve to their current form in a rainforest. $\endgroup$ – Fabian Röling Jan 8 '18 at 12:04
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    $\begingroup$ @Fabian has a good point, because humans are optimized for long-distance running, which isn't really useful in a rainforest compared with things like climbing. $\endgroup$ – PunctualEmoticon Jan 9 '18 at 10:29
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The irony is that the best way to make it untraceable is actually to add evidence.

Evolutionary paleontology operates with clues in a very different way from how you and I tend to think of them. It's not like they draw a card from a deck and find out that one of our ancestors clubbed an ape over the head with an iron pipe in the study. The inferences for our evolution, while clearly strong as a whole, are made up of many tenuous strands, like a rope that hauls barges down the river made up of thin strings.

Each of these strings takes time and energy to tease out of the dirt. That means grant money, and grant money needs to be spent on things that interest grant-providers. Follow the money. If you make it so funding organizations aren't all that interested in looking for connections to apes, there wont be money out there for scientists to go digging.

Thus, the smallest change to our geology would be to add something sufficiently grandiose and easy to find which explains our lineage in another way. You mention aliens... a really clear landing site for alien spacecraft appearing in the right places would brutally diminish the interest in searching for ape fossils in exactly the same way ape fossils have diminished the interest in alien spacecraft in our present world today!

Maybe all you need is Egyptian hieroglyphics depicting a proper alien landing instructions manual. If we knew what those pyramids were really for, we wouldn't be looking else where, would we?

Stargate pyramid landing

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    $\begingroup$ Perhaps another misleading addition would be a different fossil set that seems to very obviously suggest that humans have been around since before any of that ape evolution began. $\endgroup$ – Blapor Jan 7 '18 at 23:04
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    $\begingroup$ Re: "ape fossils have diminished the interest in alien spacecraft in our present world today": Wait, really? $\endgroup$ – ruakh Jan 8 '18 at 23:06
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First of all, Darwin created his theory based primarily not on fossil evidence (which was pretty scarce at the time), but on common traits shared between living species and on their geographical distribution. No fancy DNA analysis was needed or available in 1850's.

That said, if you want to destroy all fossil evidence, why not try biological means? Let's say that some microorganisms, endemic to Africa, destroy fossils for their purposes. Or maybe some african ants like to fortify their colonies with crushed and reglued bones. Still leaves tar pits, but these are pretty rare and maybe humans were smart enough not to fall in.

However, as I said above, even complete and utter destruction of all fossils on Earth would not prevent the theory of evolution from being developed in XIX century.

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    $\begingroup$ Maybe extinction of all other African ape species would help? We're rather less closely related to orang utans than we are to chimpanzees or gorillas. And even if someone works out that orangs are our closest living relatives, looking for human remains in Asia is going to lead you down some interesting dead ends. $\endgroup$ – Rupert Morrish Jan 8 '18 at 0:34
  • $\begingroup$ @RupertMorrish That is a great addendum, thank you. $\endgroup$ – kingledion Jan 8 '18 at 0:51
  • $\begingroup$ @Rupert Morrish: You do find fossils of early humans. pre-humans, and their relatives in Asia: humanorigins.si.edu/research/asian-research-projects/… And of course there were Neandertals and such in Europe. $\endgroup$ – jamesqf Jan 8 '18 at 3:52
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    $\begingroup$ Extinction of African Apes species would not make that much difference to theories of human evolution. Quintus Ennius (239-169) wrote" Simia quam similis turpissima bestia nobis!" meaning "the ape, vilest of beasts, how like to us!" or " How like us is that ugly brute, the ape!". The "apes" known to ancient Romans would have been Barbary Apes (Macaca silvanus), which are a species of large monkey less like Homo Sapiens than orangutans or gibbons, but similar enough for ancient Romans to comment on it. Wiping out many more simian species would be necessary to change evolutionary ideas. $\endgroup$ – M. A. Golding Jan 8 '18 at 6:23
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The Atlantis scenario

Place human evolution on a big island located on top of a supervuolcano. Humans did not only evolve there, but also invented boats to get off the island. After the humans succeeded in populating the rest of the earth, the supervlcano erupts and destroys any fossil evidence. At your discretion, the island may be totally removed after the eruption, or just changed beyond recognition (like the Greek island Santorini).

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The smallest geological change necessary to ensure that insufficient fossils exist to create the evolutionary ideas as you requested is: No change at all.

Fossils did not provide the "origin of humanity" idea in the first place

As has already been pointed out, the idea that creatures evolved from common ancestors did not originate with analysis of fossils.

Fossils may already be insufficient to trace the link you speak of

Further, even when fossils came into the equation, they did just as much, if not more, to dismiss modern evolutionary theories as they did to support it. For a long time there was a controversy called "The Missing Link." The argument went something like this (simplified for this answer): You have found fossils of humans, fossils of apes, and fossils of an extinct semi-apelike creature that is our common ancestor, but you have found no fossils that suggest the extinct creature ever evolved into humans.

Indeed, some prominent evolutionists were concerned about this and looked hard for evidence to connect the proposed common ancestors to their modern day descendants. It was even suggested by some of them that, if they fail to find some of the evidences their model suggested should exist, then the modern evolutionary model should be abandoned.

We do have more evidence now. However, the evidence is still not conclusive enough for all scientists to agree. In fact, there is a minority group (but still quite large) of scientists who do not believe that humans and apes have a common animal ancestor from which they both descended.

In science, even among people with the same (or similar) beliefs, there is a lot of argument; scientists do not all hold strong to one unified belief where they are all in concert. Even many of the supporters of the current evolutionary model will suggest that the fossil record as dug up so far is not yet sufficient to trace human origin.

Summary

The fossil record we have is enough for the majority of scientists in that field to support the modern evolutionary model, but it is still sufficiently lacking such that a reasonably large portion of reasonable scientists do not support it.

If there are smart, well educated professors and scientists who do not believe that even our current fossil record that we do have in reality is sufficient to make human evolution traceable, to the point where they don't even believe there is a link to be traced, then surely the amount of geological change necessary to suggest such a link is untraceable is zero change.

In fact, I speculate that the modern evolutionary model would still exist today, mostly intact, even if we had no fossils more than a few generations old for study.

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  • $\begingroup$ My question asks you to ignore other lines of evidence and focus only on fossils. $\endgroup$ – kingledion Jan 8 '18 at 17:34
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    $\begingroup$ @kingledion Isn't that what I did? I thought I focused 100% on fossils. Even where I mentioned "it originated with living creatures," that doesn't actually consider the evidence of it and only exists to strengthen the claims about fossils. I could remove the mention of living creatures there, and it would have the same meaning, but that would not really gain us anything. $\endgroup$ – Aaron Jan 8 '18 at 17:45
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    $\begingroup$ @kingledion There, I removed the mention of living creatures. It still reads the same though, since that was never a focus and it only focused on fossils as requested. $\endgroup$ – Aaron Jan 8 '18 at 17:47
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Climate change such as sinking the continents would work. There are no fossils on volcanic islands.

But there actually isn't any conclusive fossil evidence even now proving that humans were not transplanted or at least partially transplanted. Probably more than half the humans on earth have a different idea of where we came from depending on their religious and cultural beliefs. But to convince the academics you could either eliminate some of the key fossils eg,. Rift Valley destroyed somehow, or focus on a different belief system. Science isn't a natural progression and scientific theories change and are not automatically believed (or we'd all be in deep kimchi).

To the best of our knowledge all the key stuff went on in Africa, change the political or geographical access to Africa or otherwise make the evidence inaccessible and kiss all the key evidence goodbye.

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Soils everywhere on Earth are more acidic. Any bone matter will dissolve. No fossils of any kind. Without a fossil record it will harder to infer that there had been unknown lifeforms that preceded contemporary biota. With the possible exception of plant fossils and impressions of invertebrates in strata. However, the fossil impressions are less likely to discovered in the first instance because no-one is looking for normal fossils.

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    $\begingroup$ I feel like soils acidic enough to dissolve bone would come with some other far reaching other consequences. $\endgroup$ – kingledion Jan 8 '18 at 2:43
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    $\begingroup$ @kingledion I agree, but it would achieve the objective of the question. It is possible to assume it's an alternative world where, apart from this one change, convergent evolution and statistical ensembles of events could result in a world otherwise indistinguishable from our own. $\endgroup$ – a4android Jan 8 '18 at 7:34
  • $\begingroup$ Not all fossilized bones end up in soil. The Taung Child (a young Australopithecus africanus, and one of the most important hominid fossils discovered in the 20th century) was found in sandstone (not acidic) that had formed inside a cave located in limestone. The subsequent problem for the proposed solution of "acidic soil" is left as an exercise in basic chemistry $\endgroup$ – Keith Morrison Jan 8 '18 at 8:06
  • $\begingroup$ @KeithMorrison Interesting point. I doubt if limestone would exist on acid Earth. The trouble with making simple global changes is there will always be unintended consequences. $\endgroup$ – a4android Jan 8 '18 at 8:17
  • $\begingroup$ Just as an other example, the Hadar Formation (from which Lucy and other hominid fossils have been found) is composed of fluvio-lacustrine sediments. One would suspect that bone-dissolving acidic water moves you away from "as Earth-like as possible" rather significantly. $\endgroup$ – Keith Morrison Jan 8 '18 at 8:19
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Based on where fossils have been found so far, you'd need geological alteration of the following locations:

  • Africa from South Africa all the way up the great Rift to the Horn in order to get
    rid of the Australopithecines and early Homo such as habilis;
  • alteration of Bulgaria, Greece, and Chad to get rid of Graecopithecus, Sahelanthropus, Australopithecus bahrelghazali and Crete to eliminate the Trachilos footprints; alteration of Georgia (the country); and
  • changes of Africa and Eurasia from South Africa to the Nile, Spain to China and Indonesia to get rid of traces of Homo erectus.

So, good luck with that.

Note also that this still isn't necessarily going to work. To give an example, even without fossils being available, paleontologists had determined roughly the evolutionary history of the whales, even though the only known fossil cetaceans were already fully aquatic mammals. They were mistaken in what particular group of mammals they'd evolved from, but they had a good idea what the animals had to look like making the transition from land to water. People forget it was only about two decades ago that there was a sudden avalanche of new fossils that confirmed it.

Also, while DNA has clarified some things about what groups are more closely related to each other or what descended from what, in most cases it's DNA merely verifying what was already known. Once evolution was proposed as a method of explaining how one type of organism could become another, people immediately made the connection between humans and the apes. That was, in fact, one of the first criticisms people made of evolution because they couldn't accept that humans could possibly be related to apes, and pretty much the reason why some people can't accept it even today. Had the fossil evidence not been found, there still would have been a mountain of accumulating evidence suggesting we'd evolved on Earth and apes were our closest relative, based on analogy to what was being discovered with other species and the way science advanced.

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  • $\begingroup$ Why do we need to get rid of Graecopithecus and Homo erectus? If we get rid of everything in between, that still leaves an almost 5 million year gap in the fossil record. Surely just the first bullet point will fulfill this scenario? $\endgroup$ – kingledion Jan 8 '18 at 4:58
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    $\begingroup$ H. erectus is very clearly a primitive humanoid with a skull and jaw that starts looking very apelike and goes back 1.9 million years. If you've allowed for evolution of H. erectus to H. sapiens, and have pushed an origin back that far, you'd have to make some really convoluted explanations about why that clear evolutionary progression can't be pushed even further back in time and in form. Also again, whales: there was a 10 million+ year gap between Basilosaurus and their proposed terrestrial ancestors, and it was eventually filled. $\endgroup$ – Keith Morrison Jan 8 '18 at 5:17
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A slightly different tack to others that I think still works. edit: I missed the keyword "geological change" in the question. So this doesn't really work. But I'll leave it now I've written it.

Based on Haldane's precambrian rabbits. https://en.wikipedia.org/wiki/Precambrian_rabbit

The smallest change needed is one unambiguously Homo sapian fossil that is confidently dated to sometime before other apes (or just hominids) evolved.

This scenario would leave weird questions about why other hominids evolved to look like the already existing (transplanted) species.

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