In Praise Of In-Group Preference



I just read a couple articles pertaining to the evolution of altruism and parasitism, and the emergence of group-oriented behaviour... in singe cell organisms.
One feature is so apparent it can not be denied, the lack of complexity of group strategies in single-cell organisms.

Bacteria Pseudomonas fluorescens living in a body of water exhibit advanced group behaviour (Paul B. Rainey "Unity From Conflict"): if they experience oxygen deprivation they produce glue, the glue binds individual cells into lumps of positive buoyancy, the lumps reach the oxygen-rich surface, everyone profits. Over several generations some individuals discover that the glue works for them just fine even if they do not produce it, there is enough glue produced by others. The concentration of lazy "passengers" rapidly grows because the glue has cost, and the lazy cells experience reproductive advantage over the glue producing cells. The floating colony falls apart, stagnates or dies out.

So far nothing extraordinary, bear with me, do not jump to conclusions.

The important fact is that this cycle repeats itself consistently. Keep it in mind.

Yeast have a persistent issue with cheating (https://www.nature.com/articles/nature07921): some cells do not produce invertase enzyme necessary to break apart disaccharides, they consume glucose resulted from reactions started by other cells producing and releasing invertase. The cited authors argue that yeast as a population gets away with this shit because the invertase-producing cells benefit from 1% higher consumption of glucose (due to sheer availability) over the cheating cells, and it keeps the concentration of the cheating cells at a tolerable level (also this cheating strategy is facultative for the yeast individuals, it helps to maintain the balance).

Again, the key factor is the persistence of the issue, against which the population does not do anything, they all simply tolerate it.

Bacteria Myxococcus xanthus practice fruiting bodies that fall prey to cheaters (https://www.nature.com/articles/nature04677): a fruiting body is a sacrificial behaviour most of the cells forming the body doomed to never reproduce, unsurprisingly it invites cheaters, a genetic line of M.xanthus that specializes on attaching themselves to other's fruiting bodies as spores. This line is incapable of doing the "altruistic" part of the job, when present in a healthy colony, they make sure they reproduce while others facilitate the process, when they outnumber the healthy population, they all die out, because nobody produces fruiting bodies.

Why are there M.xanthus around still? From time to time a mutation happens in M. that somehow prevents a cheating cell to attach to a normal fruiting body. Perhaps this mutation is in balance with the one causing the cheating behaviour. So, both lines reproduce. You may say "by chance". Those mutations come and go, sometimes the healthy line reproduces, sometimes the cheating line. And again, the lesson is never learned. Every new colony faces exactly same problem and repeats exactly same history.

The exactly same issue is observed in amoeba Dictyostelium, with the same outcomes.

This tragic vulnerability to cheating among all social single-cell organisms poses a serious question: HOW? do they retain altruistic strategies or any social behavours at all?

Pure statistics offers an answer: Simpson's paradox, which is not a paradox at all. Let's start with a population with a known concentration of cheaters, say 1/2. Then we divide this population into several isolated populations with varying concentrations of cheaters, from significantly higher than 1/2 to significantly lower than 1/2. For simplicity's sake, let's say we split the initial population in two halves: one contains 3/4 cheaters and another 1/4. Now let them grow independently. If altruism has any societal value, then we expect the latter colony to outgrow the former. At the same time, since our singe-cell friends have no means to counteract cheating, the concentration of cheaters grows in both populations, say from 3/4 to 13/16 and from 1/4 to 5/16. It is then possible that the concentration of cheaters on average still dwindled, if the low-cheating population increased in its size sufficiently. For example, the high-cheating population doubled, whereas low-cheating population quadrupled, then the concentration of cheaters in the combined population will be: (2 * 13/16 + 4 * 5/16)/6 = 0.479 (the new size of the combined population is 6).

The numbers do not lie, but IRL there is one problem: who is dividing and re-combining those populations to produce the shown effect?

John S. Chuang, Olivier Rivoire, Stanislas Leibler experimentally demonstrated in "Simpson's Paradox in a Synthetic Microbial System" that such conditions do naturally occur... rarely... like VERY rarely.

On the other hand the altruistic behaviours listed above are themselves SCARCE in the single-cell world. Still no surprise here: rare conditions produce rare behaviours.

However, in humans, mammals, and multicellular organisms altruism is as abundant as dirt. What is the key difference?!

Unlike yeast, we all have sophisticated counter-cheating strategies. And it is most likely we evolved them through group selection, in competitions between rival groups. It is easy to see (it is almost a no-brainer) that a society of cheaters is at a massive disadvantage against a society with prevalence of honest cooperation. Whereas cheaters have individual advantage against altruists within a society, they tend to cripple their society and die out altogether with the entire society -- thus a society who develops a counter-cheating strategy automatically receives a competitive advantage, and counter cheating strategies evolve. This is as obvious and self evident as basic claims of Darwinism. If you are not satisfied, E.O.Wilson argued the role of group selection exhaustively from every possible angle, read E.O.Wilson.

But wait! What makes it impossible to run an analogous group selection in yeast?

Let's do it. Let's run a thought-laboratory in which we breed yeast for counter-cheating behaviours. Let's set up a row of vials with tasty sugars and observe how honest are the yeast towards each other. Over many generations we would expect some diversity between vials, some will keep their cheaters at bay, some will fail. Already we can see a fatal problem: a failed colony does not free its food source for others to consume, it is being isolated in a vial, a thriving colony does not threaten neighbouring vials -- all vials are completely isolated, no information exchange, no resource transfer takes place. We must fix it. We must use our godly powers to reward well organized colonies and punish poorly organized, and necessarily include COPYING of successful colonies in the reward. Here we are, breeding yeast for social skills by means of artificial group selection. So far nothing prevents our future success.

Over 10 000 generations we bred highly social yeast and then released them in the wild. What happened? THEY MIX with the wild yeast, echange genes, experience the pressure by wild cheaters, and our carefully bred strategy gets diluted. "Suddenly", there is no mechanism in yeast to maintan A GROUP. Whatever yeast occupy a bottle of tasty sugars, they are all just homogenous yeast. All of them reap the reasults of our specially bred invaders, and all of them bear the cost of unwise behaviours of everybody else -- almost perfect "equality", only restricted by convection and diffusion.

BIG SURPRISE: THERE IS NO GROUP SELECTION WITHOUT THE EXISTENCE OF GROUPS.

But we, humans, have a powerful tool for maintaining a meaningful group despite physical mixing: SEXUAL PREFERENCE.

Sexual reproduction allows for sexual preference,
Sexual preference defines groups,
Groups compete in the Darwinian framework resulting in group selection,
Group selection enables traits that are not possible for individual selection: altruism and counter-cheating,
Counter-cheating makes altruism profitable,
We observe the abundance of altruism.

I dare say our counter-cheating capabilities result from the fact we reproduce sexually -- and this is THE difference from the single-cell half-baked altruism.

!!! ENJOY YOUR SEXUAL PREFERENCE !!!
It is the bedrock of the civilization as you know it.
The visceral disgust for miscegenation makes biological sense! You evolved it for a benefit of your kin, don't let an ideology revert what The Mother Nature had built.
All that you consider noble and praiseworthy in humans, had arisen due to the millennia of rampant xenophobia -- the visceral xenophobia (so much condemned by leading ideologues) itself is THE CAUSE of altruism.




APPENDIX
(optional read)


The origin of the sexual reproduction is a long standing problem of evolutionary biology: why on Earth would anyone complicate his life with such a HUMONGOUS IMPEDIMENT for one's reproduction, while every turn of global evolution demands babies, more babies, MOAR BABIES, how could it possibly be beneficial for anything, and exactly what for... I beg your attention, we came extremely close to the correct answer.

I can not say (however tempted) that the aggregate advantage of altruism paired with effective counter-cheating is the cause of the invention of sexual reproduction -- I only demonstrated the necessity of sexual reproduction for the particular advantages we achieved, and the benefit of sexual preference (selective mating) -- but the sexual reproduction precedes the sexual preference, and the original (prime moving) benefit of the sexual reproduction is yet to be found.

In our imaginary yeast laboratory we accidentally illustrated two fundamental deficiencies of sexless reproduction in general: 1. each vial is a complete Universe, no information leaves a dead colony -- the yeast do not have any means to learn any lesson from other's failures (it does not mean if they lack other faculties to learn in any sense, as long as there is this communication breakdown preventing even a theoretical possibility of developing such faculties) -- this issue is paralleled by real life, they do live in isolated islands with very little to none foreign contacts; 2. each vial is practically homogeneous -- they do not split into rival groups because physical mixing.

We do solve the 2 with selective mating (and other means too, of course), whereas the 1 seems harder to crack. Apparently we do engage in intergroup conflicts that provide some degree of exchange of information, including genetic information from defeated groups, and this information is gendered (all Y's are either killed or enslaved, whereas most X's successfully reproduce with the victorious group) -- it is not mixing, it is strictly filtered exchange, and on top of it we can learn what behaviours lead to defeat. Still it is very high-level effects, something deeper is needed.

A sexless colony has no sex-related issues that incapacitate the colony. Sounds tautological? This colony stops reproducing when it dies. Died = silent.

Whereas a sexful colony (due to the mate acquisition cost) must fail to reproduce some time BEFORE it physically dies out. There must be a period of time when a failed colony is capable of disseminating the information about its failure because the members of an already doomed colony are still physically alive. This heterochronicity is introduced specifically by the "HUMONGOUS IMPEDIMENT" of sexual reproduction.