Suppose humans discovered a beautiful new world they wanted to inhabit, far from the political machinations and military affairs of the alien-populated universe. They established a few colonies on the planet's surface, with differing levels of technology.

One of the native fauna serves as an agent of change: it is similar to a mosquito, but each bite slightly alters the genetic structures of its victim. This allows flora and fauna alike to adapt to their environment. Humans, for example, cannot eat the local food until a few days of exposure to the mosquitoes alters their body enough to make the food compatible.

This change needs to be slow enough to

  1. keep the victim alive and
  2. prevent the changes from being quickly noticed,

but fast enough to

  1. be obvious enough to distinguish someone living on the planet for years from someone who just arrived.

My current idea is for the mosquito bites to modify 1% of the subject's unaltered genetic structure each year. Over time, these changes manifest as unusual hair or eye color, hardening of the skin, and similar predominantly cosmetic changes. Across generations, these changes are much more profound, such as introducing new organs or appendages.

My Questions

  1. Is this a reasonable rate of change to achieve my three objectives?
  2. How can I calculate the amount of genetic change a given individual has experienced for a given number of years of exposure?
  3. How can I calculate the amount of genetic change between generations?
  • $\begingroup$ Makes me think of this idea. $\endgroup$
    – JDługosz
    Nov 22, 2016 at 19:43
  • $\begingroup$ There are a number of problems with this scenario, immune response as described by AndreiROM being just one of them. The main thing is you've massively underestimated how impactful small changes in DNA can be, it also seems unlikely that an alien virusesque thing can meaningfully interact with human DNA. $\endgroup$
    – Tim B
    Nov 22, 2016 at 20:03
  • $\begingroup$ @TimB I'm open to suggestions for better mechanics that solve my problem while holding to my premise. The mechanic itself has, so far, been just a handwave. I may ask a question later about the mechanic... $\endgroup$
    – Frostfyre
    Nov 22, 2016 at 20:10
  • $\begingroup$ This is a good idea in principle, but some things need to be addressed to make it feasible. [1] It's worth noting that changes to DNA are made to embryos - when we genetically modify organisms, we modify them before conception, which allows extra traits to develop in the womb. Is there evidence that mutations can occur after birth while still changing physical structure in this way? $\endgroup$
    – Zxyrra
    Nov 23, 2016 at 0:02
  • $\begingroup$ [2] DNA changes must be spread to cells other than the infected for an actual change; you must provide a method for this. $\endgroup$
    – Zxyrra
    Nov 23, 2016 at 0:02

2 Answers 2


You're effectively describing a virus - an organism which injects its own DNA into an existing cell, and re-purposes it.

And the answer is that the sort of slow change you're looking for is not going to work.

Why? Because iffy things happen when cells starts displaying characteristics which your immune system can't recognize. It's why people who've had organs replaced have to take immunosuppressants.

And so, the infected cells would be attacked by your body. You'd run a fever, and maybe start manifesting worse symptoms as your immune system went on the offensive and failed to deal with the infection.

The only way for an organism (human, in this case) which is already born and alive to survive a change to its DNA (assuming that the change itself does not result in some terrible disease, etc.) is for that change to be implemented throughout the entire organism in one quick go.

The event would have to be very, very fast and aggressive. The subject may even suffer clinical death in the process, but be revived by medical teams, or the virus itself by some clever mechanism. Keep in mind that this is science fiction, and that a doctor would most likely say you'd simply die.

  • $\begingroup$ So the slow change wouldn't work even if the virus suppressed/replaced the immune system first? $\endgroup$
    – Frostfyre
    Nov 22, 2016 at 19:51
  • 1
    $\begingroup$ I disagree with this, the slow change would be fine so long as the immune system was either suppressed or updated at the same time. In fact immuno-suppression could be the first symptom. $\endgroup$
    – Tim B
    Nov 22, 2016 at 19:53
  • 1
    $\begingroup$ @frostfyre - if you suppress the immune system then your subject is simply going to die of some other disease. $\endgroup$
    – AndreiROM
    Nov 22, 2016 at 19:54
  • $\begingroup$ @AndreiROM "he only way for .... the entire organism in one quick go." This is not true. Every complex living thing is laden with small and insignificant mutations. A small change in your DNA can cause 2 things: a detectable mutation that is identified by your immune system and cellulair cancer defense mechanisms. Or it can cause absolutely nothing; you just have slightly altered DNA in a single cell. $\endgroup$
    – Wissieze
    Jun 14, 2017 at 20:31

Look at it from the opposite point of view. We and chimps and bonobos share 99% of our DNA. Have you ever heard of a virus which has changed a person into something resembling a chimp? That would be a 1% change.

How long would that change take? I'd guess at least a couple of dozen to a couple of thousand generations. 1% a year? No way. Changes on that time scale would have to be orders of magnitude smaller.

Consider that the human body "turns over" about every 7 years (crudely speaking). So, each "stage" of change should be about that long. And if it takes, say 10 changes to develop the entire new enzyme/metabolic pathway to digest a new food, then that's 70 years or 3-4 generations (and much less than a 1% change of the human genome).

Consider some of us have the ability to digest lactose. Read up on how long that has taken. I grant you that "intelligently designed" changes could speed up the process considerably, but changing too much at once (in a single organism) just isn't survivable. That's why death is part of life.


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