Installment Three, Genetics in the 24th century: The Trouble with the Trouble with Tribbles

Hang on to your hats, Trekkies, because I’m going to go after “The Trouble with Tribbles”. The Trouble with Tribbles was the 44th episode in the original Star Trek series and was written by Science Fiction legend David Gerrold, who also wrote the Martian Child, which was turned into a great movie. Gerrold wrote two of my favorite novels, When HARLIE Was One and The Man Who Folded Himself.

The Trouble with Tribbles has been hailed as one of the best episodes the franchise has ever put out and I can’t disagree. I love David Gerrold. I am a huge fan. (Do not worry. This post does not involve physics of any kind. No need to break out your Calc III notes or bone up on abstract algebra or quantum mechanics or quantum computing. Check your manifolds at the door. It’s all easy peasy science. Oh and check your inner critic and your studly fan powers at the door. This is about the science not the story. The story is beautiful, the science less so. If you have not read the other two installments: click here for installment one and click here for installment two before reading this post.)

The problem with the Trouble with Tribbles is that when a tribble is born, it’s already pregnant¹. Thus, the trouble with ‘Tribbles’ is that the inbreeding coefficient would be 0.5, meaning that the parent self-fertalized. Half the child’s chromosomes would have their “partner” chromosomes replaced by a copy of themselves. That means that every tribble born would have a maximum chance of genetic damage. The child would be like a clone of the parent except with massive genetic damage. In other words, there is a very good chance the tribble would not survive birth.

But let’s say that when the male “partner” first impregnates a female tribble that it also gives genetic material for the creation of the fetus that develops inside the tribble being born. That would put the inbreeding coefficient at 0.25 because the egg for the fetus came from the child and the egg for the child came from the mother thus both the sperm and the egg are duplicated. If the father is inbred, and with tribbles you already know that they are, then the coefficient will be higher, almost approaching 0.5. So, even in this scenario, expect genetic damage.

Finally, the more inbred a population, the more likely the coefficient will approach 1. It may even be 1 but it will not exceed 1. (If you believe me about the tribble inbreeding and don’t care about the math, click here.) “The mathematical reason for this is that although the basic formulae for R and F are Σ(1/2)ⁿ and Σ(1/2)ⁿ⁺¹ respectively, as inbreeding within a line progresses, the correction terms applied to R for inbreeding (see here) gradually become more important and start to reduce the value of R below Σ(1/2)ⁿ.” Taken from “THE COEFFICIENT OF INBREEDING (F) AND ITS APPLICATIONS.”

The method of calculating the F coefficient of an individual is similar to that for the coefficient of relationship (R) between two collateral relatives, and involves the tracing of paths between the two parents via a common ancestor. R denotes the proportion of genes that are held in common by two individuals as a result of direct or collateral relationship. Collateral relationship are individuals who are only related through common ancestors, e.g. cousins.

Equation 1 method of calculating the F coefficient of an individual (F measures the probability that two genes are identical by descent from the common ancestor(s) of the two parents).

To sum up, genetically, Tribbles and their offspring would not be genetically viable even with super alien DNA.

Why is this? How do I even know that they have human-like DNA or any type of DNA at all? First of all, the episode The Chase, a story in five acts. The punchline to this story is that 19 races or more in our galaxy have one single progenitor. Thus explaining why every alien in the Star Trek world looks more or less human. Not only morphologically and phenotypically, but also genetically. Don’t forget, they all can interbreed as seen in various episodes starting with Spock in the original Star Trek series. Spock is half human and half vulcan.

However, let’s say that the tribbles are original galaxy stock. They evolved separately before the seeding began and adapted to the biochemistry of the progenitors. Well, any organism that reproduces sexually must pass on their genetic traits somehow. If they don’t have human-type DNA they must have an analog to DNA and RNA, for that matter. The math might be slightly different for the tribble DNA-analog but in the end the inbreeding coefficient will produce genetic defects. R and F will eventually get you.

So my conclusion stands, Star Trek is science fantasy at best and fantasy in science fiction drag at worst. But I still love the show. See my two previous posts: Installment One of Physics in the 24th Century and Installment Two of Physics in the 24th Century: the transporter, science fiction or fantasy?

^{1. This means we can rule out cloning and budding. Pregnant implies two partners. But even if we assume that tribbles bud, then why are there so many phenotypes? It seems unlikely that they reproduce asexually.↩}