Backstory I have a race of biologically advanced aliens that develop by fighting, adapting, and growing immune to the current highest standards of technology a species has to offer. By doing this they've come to "farm" planet earth for it's technological prowess towards weapons. Once we evolve to a new standard of weapon they show up, wipe us out, destroy all trace of that civilization and then reseed the earth to do it all over again in several thousand years or when we assume a new technological advancement.

My Issue With this backstory in mind I've come to see that the issue of "wiping" out all human involvement in the planet would be hard, but even given say countless workers, and a species capable of changing into anything, could this species effectively remove say today's civilization off the map to a point it could be nearly gone, and anything left standing would return to normal over the next several thousand years of evolution as a new primitive man evolved again?


closed as too broad by F1Krazy, JBH, Don Qualm, jdunlop, Frostfyre May 2 at 20:41

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    $\begingroup$ Hi, @Alexander Duppong, welcome to Worldbuilding! You seem to be asking a number of questions at once. Could you please focus on one question so it can be properly answered? $\endgroup$ – Alexander May 2 at 18:44
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    $\begingroup$ When you refile this as multiple questions, do make sure you say how long the cycle is, how thoroughly you need the cleanup to be done, and exactly what you mean by (3). Cos that last bit sounds a bit like asking where babies come from... $\endgroup$ – Starfish Prime May 2 at 18:58
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    $\begingroup$ Welcome to Worldbuilding.SE. Please click here to learn more about our culture and take our tour. This question is too broad. (a) You're asking three questions on a site designed to allow only one. (b) Questions #1 and #3 are MASSIVE. (c) Question #2 depends on circumstance. Oral histories can last a very long time. Anyway, our help center explains that questions must be specific and answerable, must include context, must include restrictions/requirements, and should include research. Can you edit your Q down to size? $\endgroup$ – JBH May 2 at 19:09
  • $\begingroup$ Nice try aliens.. $\endgroup$ – Fels May 3 at 7:04

Removing "all traces" might be difficult: mining endeavours delve into layers hundreds of millions of years old, so you'd need to wait at least that long for new crust to be formed and intact mineral deposits to reappear. Even so, very old cratons would survive and their isotopic ratio and composition might give the game away.

Unless you had the technological level and power to reform the planetary crust, essentially 3D-printing a pristine surface every time complete with artificial isotopes. That could be achieved comparatively quickly: the land surface is about 150 million square kilometers, and if you had machines capable of restoring one square kilometer per year, 150,000 of them could do the deed in a paltry one thousand years.

Keep the seed population numerically stable in separated enclaves, understimulated and half-doped, barely able to care for the children, and within three short generations culture will have disappeared, and maybe language too. You just need to supply them with water and food so they don't starve and don't need to reinvent agriculture.

When the planet is ready simply open the enclave and force the people out of the Garden of Eden, to work for their food.


It all boils down to what kind of traces the previous occupancy left. This in turn depends on its technological level. Bronze Age civilizations managed to dig sizeable copper mines, whose remains are still to be found today. More to the point, the copper isn't - it's locked in wires, pipes, rain-gutters and so on. Destroying said pipes and rain-gutters would simply enrich the environment with minute quantities of copper oxide particles, not reform the original copper ore.

So, the next occupancy might or might not find the holes where copper mines were, but it's a given that they won't find much primeval copper ore to process. The same goes for almost all other metals, except maybe for iron (there are biologic processes that concentrate iron ions into harvestable bog iron).

You can harvest the population, and re-seed it - then what happens? The next occupancy will not be able to reestablish a technological base with the same ease, since any easily reachable mineral deposits will already have been depleted. This, of course, will not prevent their being fruitful and multiply, and establish a primitive civilization in the following thousands of years, when the harvesting cycle can start again.

What it's unlikely you'll be getting is a technological, let alone advanced civilization anywhere beyond the first cycle.

  • $\begingroup$ So what if my alien race was biologically superior. Primarily through adaptive evolution. I toyed with the idea of having a species of "eaters" that would tear down and destroy modern architecture, and release bio organic compound. The aliens replicate themselves using the resources of the planet they land on, so using these two ideas combined with yours, would it work for the aliens themselves to slowly adapt and become this new layer of pristine surface in some way working within their means to terraform? $\endgroup$ – Alexander Duppong May 2 at 20:48
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    $\begingroup$ @AlexanderDuppong it would work for a very low level technology (on the victim's part). Already with 1850 technology Earthmen would suspect something strange is going on. However, an organic layer like that would mean next to no extractable minerals, and therefore almost no technology at all. The second (and following cycles) would have to take place with Stone Age populations. $\endgroup$ – LSerni May 2 at 21:05
  • $\begingroup$ I've reworded and added to the question to help get a more precise answer to what I'm working towards. $\endgroup$ – Alexander Duppong May 3 at 15:01

One way I can think of is induced amnesia. The idea is to repeat the Adam and Eve creation in Eden. Selected couples are chosen for the next generations. A drug therapy wipes-out their memory. That makes them think they have been just created by God, or a god of some sort. They are taken care of within the depths of a jungle with good conditions to start a new civilization. Preserved sperm and eggs enrich genetic diversity through artificial insemination that is staged to look like divine intervention.

Meanwhile, the aliens have time to wipe-out any marks of past civilizations and restore urban spaces to their natural state. Buildings made out of stone are crushed into sand, glass as well, machinery and metallurgy processed into metal oxides and buried in the soil. They will appear as natural deposits to future civilzations, before the next "rinse". Burial places may be selected to match original mining sites, so that deposits will not appear "out of place". I guess precious gems must be crushed as well...

It's by the way a huge undertaking. The aliens must meticulously map the Earth for man-made structures. It may take years of intensive work to carry-out the job.

  • $\begingroup$ Please note the Help Center suggests you should only answer well-asked questions. $\endgroup$ – JBH May 2 at 19:20
  • $\begingroup$ I've reworded and added to the question to help get a more precise answer to what I'm working towards. $\endgroup$ – Alexander Duppong May 3 at 15:02

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