first science fiction story that deals realistically with population genetics?

Question

Many, many science fiction stories involve growth of a population from a small initial population (e.g. TV tropes' Adam and Eve plot). I just read H. Beam Piper's Genesis (1951), in which Homo sapiens is supposed to have evolved from the survivors of fewer than a dozen stranded Martians; according to this question, the Star Trek IV "restore the global humpback whale population from two individuals" problem was finessed in Vonda McIntyre's novelization by saying something about reintroducing genetic diversity from stored tissue samples.

I can imagine that there are stories where people think carefully about effective population size in the context of generation ships (see this journal article linked by Wikipedia) ... but I haven't come across them and would enjoy reading them.

I am interested in "hard" examples that carefully explain the problem and solutions, rather than hand-wavy explanations.

In the interests of making this on-topic, I will ask for the first such instance (modern population genetics started in the 1930s, although clearly people understood the problems with inbreeding before then ...)

Answer 1

1952: "No Land of Nod", a short story by Sherwood Springer, first published in Thrilling Wonder Stories, December 1952, available at the Internet Archive.

I don't know how realistic the science is, because, like the guy in the story, I wasted my time reading science fiction instead of doing my homework. Anyway, the characters in the story, the Last Man and Last Woman on Earth, do take the genetic problem very seriously, and they read up on genetics before they decide (SPOILER WARNING) to try and repopulate the world.

"I mean, here we are alone in the world. After a while we have two or three children. They grow up. Then what?"

She hesitated before answering. "That's a decision we have to make," she said gently, "before we have the two or three children."

He shook his head.

"But suppose we do decide to have them. What happens then? Where are their children coming from? You can't mate brother and sister. Look at the idiots that have been born just because cousins married."

"That's the decision I mentioned. Genetics wasn't my field but I know a little about the subject. You’re not altogether right about the idiots. Idiots have been born to cousin matings, I'll grant you, but thousands have also been born to couples who were not even distantly related. Heredity is a matter of genes, passed down from generation to generation, and whether your child is an idiot or not depends mostly on whether the black gene of idiocy runs in both blood lines. If it runs in yours, and the girl is also your cousin, it will probably be found in hers too. A mating, in that case, would be almost sure to bring out the worst.

"But suppose you took healthy, intelligent parents who were both free of black genes. The chances are their children would be superior to the ones born from the average marriage. And if you bred these superior children there's no reason to suppose the third generation would be a bit less superior. A dominant strain strengthens itself. Surely you remember something of what the farmers and breeders were doing with animals and crops?"

"You almost make it sound all right," Jim admitted. "But how do we know about these black genes? You and I might be crawling with them."

Ann was forced to smile at his words. "We'll see. When we get to Jackson I want you to find a bookstore or library. I think we can get the information we need, and then we can take inventory."

[. . . .]

The huge gasoline tanker they had picked up in Birmingham as a solution to the increasing problem of fuel evaporation, ground to a halt and, as Jim set the brake, Ann climbed down from the cab and made for the doorway of a bookstore. When she reappeared thirty minutes later she carried seven or eight volumes under her arm.

[. .. .]

Ann opened one of the books to a page she had dog-eared, the beginning of a long list of the particular genes that science had demonstrated were responsible for most of the hereditary ills of mankind.

"For once," Ann began, "we must be completely honest with ourselves. If either of us is, or has been, affected by any of the conditions listed here we must make a note of it. Our parents and grandparents, too — let's rack our memory of them, and other members of our family trees. Think hard while I call the roll.

"Diabetes."

Their answers were both negative.

"Insanity, or feeblemindedness."

Again negative.

"Epilepsy. There seems to be some dispute about this one's being hereditary, but let's not skip it."

"Nope," Jim said. "No epilepsy." Ann added her "No" and they went on.

Answer 2

You could make a case that "The Voyage that Lasted 600 Years"(Donald Wilcox, Amazing Stories October 1940 is the first.

This is one of the earliest true Generation Ship stories, and along with a number of other things (about the only trope he missed is the crew and passengers forgetting they're aboard a starship, which Heinlein neatly picked up the next year with the novellas that became Orphans of the Stars), eugenics (in its original meaning, not the crutch for racism that it was sometimes used as) is brought in -- which at least implies that the mission planners (and the author) considered the then-available information on population genetics such as minimum population size, ways to avoid genetic drift, and so forth.

I haven't read the story, so I can't say confidently it discussed this subject as a serious scientific one, but for the day, merely acknowledging it existed was a good start.

Answer 3

I will discount the "first" criterion, since I think that will depend on what you end up accepting as candidate plausible answers. I suspect there won't be many. I will offer a review I posted to usenet (rec.arts.sf.written) about 30 years ago, one of a series of reviews of "BioSF" - hard SF based on biology. I don't know of a rasfw archive site to link to, but it's my review so I will copy the whole thing below.

Courtship Rite (1982), Donald Kingsbury. (UK title: Geta)

If Dreamsnake is the most-awarded book on my list of biological SF, then Courtship Rite must be the least-awarded but most deserving. It did not win either the Hugo or the Nebula for 1982. It did make the Hugo ballot, but lost to Cherryh's Downbelow Station. Courtship Rite has imaginative world-building, engaging characters, good though not brilliant prose, humor, a thriller of a plot, and, key to its appearance on this list, a hard-SF premise based on biochemistry and genetics. Cherryh has shown all of these in one work or another (I'm sure at least one Cherryh title will make it onto my BioSF list), but Downbelow Station is not one of her stronger novels. Courtship Rite beats it on every count. Kingsbury's web site says that he is working on another book set in the same future, so perhaps Courtship Rite will see republication soon. It certainly deserves it.

Courtship Rite is set in the far future on the world of Geta. Geta was, just barely, suitable for human colonization. The plants and insects are inedible, and conversely the microbial life of Geta cannot tolerate (nor pollinate) imported Terran plants. The colonists had no choice, so they stayed. They survived on laborious hand-cultivation of a small number of Terran plants, equally laborious husbandry of a small number of Terran insects, and extreme measures to ensure the continuing fitness of the human population. At the start of Courtship Rite, the colonists have survived for long enough that the details of their arrival on Geta have become legend, and highly disputed legend at that. The horse is a remembered only in children's rhymes. The exodus from Earth is remembered only in oral tradition and a few scraps of writing. Terran history was not a survival skill; it was lost. Biochemistry was most definitely a survival skill; it survived, and biochemists constitute the combined priesthood and ruling class of Geta. The very word "priest" in Getan is perhaps best translated as "biochemist", although it takes a while for the reader to pick up on this. Kingsbury immerses us in the Getan mindset right from the start, but cleverly leaves the significance of many Getan word usages to be picked up by context.

In brief, the plot of Courtship Rite chronicles the start of a technological renaissance on Geta, told from the vantage point of one Getan 'family' (perhaps best translated as 'commune') who are centrally involved. There is political intrigue, an engaging look at the [re]discovery of electromagnetism and information theory, and a central thriller of based on thwarting the simultaneous advance of a bioengineered crop-destroying pest, a mind-destroying plague, and a planned military invasion by a neighboring clan/state.

The Getan preoccupation with 'kalothi' (translation: 'Darwinian fitness') permeates everything from political theory to social planning to marriage (hence the book's title). Getan famines are frequent, and in time of famine only those with high kalothi will survive. To forestall wastage of scarce food supplies, the local priesthood will have ranked their clan members in advance as to their relative kalothi. When the famine comes, those with low kalothi will 'contribute to the clan' so that those with higher kalothi will survive. (translation: they will be killed to feed the rest of the clan when other food is scarce). Yes, cannibalism is common on Geta. One may debate whether it is in fact necessary on Geta, given the paucity of native food sources, but whether or no, it has become ingrained in Getan culture.

Politics follow. Each competing priesthood has some policy for deciding how kalothi is rated, and clans may attach themselves to that priesthood if they feel that policy is to their favor. Some priesthoods rank kalothi through annual competitions in the kol-game, a game that seems to be part board-game, part Sim-City, part genetic modeling. Others, in particular the Kaiel, cull their clan members in childhood even in good times, pre-selecting for a population that will both be fit and have well-stocked larders. Fortunately for those of low kalothi, times have been good of late, so the hard choice of contributing to the clan has not been required of many. But the advancing crop-destroying pest will change that in a hurry if it is not stopped.

The maran-Kaiel family are members of the Kaiel priesthood, biochemists and politicians all, though Hoemei and Gaet are more inclined to political theory, while Joseai and Teenae are more inclined to advance politics by threatening a rain of pebbles (translation: 'bullets'). The cast of characters is large; in addition to the maran-Kaiel we are introduced to their prospective bride, Oelita, and to a shadowy clan of courtesans, the Liethe, who prove central to Geta's future.

The Liethe, by the way, have dealt with the issue of kalothi by limiting their reproduction to cloning. Courtship Rite manages to present one of the most plausible takes on human cloning I can think of in SF. That alone would be enough to make my BioSF list, but in fact it's just a side note to the main story.

As with Dreamsnake (BioSF review #1), I find the most compelling feature of Courtship Rite to be the vision of future biological research and applied bioengineering carried out largely without recourse to the mechanical tools and laboratory chemistry that are so familiar today. That's a road we are on already, and we've progressed a good way down that it in the 20 years since Courtship Rite was written. The reagents we use today, from restriction enzymes to co-expressed chaperonins to tailored plasmids to... hmm, let me just summarize by saying that compared to even 20 years ago, an unbelievable number of the tricks and tools used in the lab today are produced by cleverly engineered microorganisms, domesticated animals if you want to look at it that way. On Geta they don't need a room full of mechanical DNA sequencers to probe the genome of an invading pest; they can read off its DNA sequence by using tailored bacteria. That's a trick we can't quite pull of today, but I can almost see how you might start to work on it. I can only applaud Kingsbury for having the vision to see that this level and type of technology is well within the range of the possible. Again as with Dreamsnake, it is much more plausible that a marginal society will maintain biological high-tech if it is based on renewable apparatus: bugs rather than NMR machines.

Courtship Rite also tackles issues of human genetics and eugenics. Geta has a planetwide society obsessed with Darwinian selection applied to socially advanced humans. The survival strategies taken by various Getan priesthoods may arguably be unworkable, but that does not detract one bit from the overall plausibility of the story. Some priesthoods get it wrong, and they fail to survive. Others get it right; they survive, and clans flock to their leadership hoping to survive with them at the time of famine. But, right or wrong, all of the factions of Getan society are shaped by their understanding of biological fitness, and Courtship Rite is a marvelous view of how such a world might play out.