Modeling genetic diversity

One of the factors in achieving the main goal of Frasgird — survival of the human race — is creating a population in the colony with sufficient genetic diversity (and size) to allow it to progress. One of the backstory assumptions is that the various scattered human settlements (almost all of which are on predominantly alien occupied worlds) have had too much isolation during the post-huida centuries since the last big quantum quake, during which technology had to readvance to allow interstellar travel to start up again, etc. Even after space flight re-emerged, there wasn’t the same incentive (as there was to flee Earth) to travel from world to world in large groups; instead, the colonies and settlements tended to focus on surviving and thriving locally. Some of this isolation led to pathogen vulnerability, particularly when many of those pathogens were not of Earth origin.

At the same time, as genetic engineering technologies were rediscovered or simply re-implemented, some of these settlements did gene therapy to better adapt to their existing environment. So you had issues of both genetic uniformity within a given settlement and genetic drift between settlements. And as the population of at least some of the settlements begins to decline, they are less able to recover.

Frasgird itself, when it starts out, has a human population that is likewise too homogeneous and drifting from others. One of the explicit goals of the game is to increase the genetic diversity (including overall population) to a sustainable level. This is done by enticing immigration to Frasgird from other, still existing human settlements, as well as the retrieval of cryogens (‘green ice’ pods) that contain Dryas-era humans.

The question, then, is how to model genetic diversity in the settlements and in Frasgird. The abstraction should be relatively straightforward but should allow for unexpected or unanticipated results in combination. My first idea is a number of ‘allele clusters’, each with an integer value (>=0) representing the number of variant alleles in that cluster. The higher the value, the more genetic diversity in that cluster of traits. When some number of people from one population are added to an existing one (e.g., some number of immigrants arrive at Frasgird), the new genetic diversity is weighted by the size of the immigrant group — thus, bringing a handful of people into a large existing group doesn’t help all that much — at least, not at first. As technology advances (via cryogen openings), the colony may gain genetic engineering tech that allows direct propagation of alleles without the slow and uncertain step of interbreeding for several generations (which itself is not guaranteed success unless the incoming population is sufficiently large).

I think with a bit of experimentation, we can come up with a relatively simple model that will produce the results we want and that will leave the door open to impacts such as outbreaks of new diseases among insufficiently diverse populations.


Filed Under: GeneticsMainModeling

About the Author

Webster has been doing game design since 1980, but only has one actual published game to his credit -- Sundog: Frozen Legacy (Apple II, 1984; Atari ST, 1985). This is his second.

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  1. […] the abstracted layout of the colony, we also need to model the population dynamics — numbers, genetic diversity, and so on. At some point, to increase the probability of humanity’s survival, groups of […]

  2. […] about 25 births/year — again, absent incentives to raise the birthrate.  However, to achieve the necessary genetic diversity, you will need not only to encourage live births, but to encourage intermarrying between groups […]

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