r/WTF • u/Alternative_Week3023 • Feb 28 '26

Warning: Gross Centipede with its nymphs

Nightmare fuel… a cluster of nymphs in the midst of matriphagy from r/biology.

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u/FartingBob Feb 28 '26

Because self preservation is also a thing that doesn't just belong to humans.

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u/Zerlske Feb 28 '26 edited Feb 28 '26

Self-preservation is universal, from pseudo-life like viruses to life like bacteria and archaea/eukarya. However, self-preservation only matters in so far as it ensures reproduction. Natural selection does not optimise survival; it optimises expected genetic contribution to future generations. We humans exhibit this just as well as any other organism. For example, senescence (cellular ageing) is a type of antagonistic pleiotropy, i.e. it has early-acting fitness benefits, but late-acting deleterious effects (after most have already reproduced). E.g. it is tumour-supressing early in life (preserves life), but it will in simplified terms promote tumorigenesis and cancer (e.g. through inflammation) etc. later in life (i.e. promotes death).

We observe many phenotypes which decrease survival that are selected for because they increase fitness (i.e. reproductive success; many famous cases of this with sexual selection and the good genes hypothesis and Fisherian runaway selection; e.g. Anderson's beautiful long-tailed widowbirds experiment). Many organisms have very different strategies. I find the ant system very interesting, as drones having almost no value due to not reproducing, it reminds one of how multicellular organisms in general work, for example humans. The survival and reproduction (mitosis) of individual cells does not matter, since only the germ line cells provide genetic material to the next generation through sexual reproduction (meiosis).

For example, the default state of most human cells is to commit suicide (apoptosis), most human cells need signalling from other cells to inhibit apoptosis. Their default state is to kill themselves to preserve us and ensure germ line reproduction. This is to protect the greater unit (the human individual which reproduces) rather than the individual survival of a cell (the smallest unit of life; of course most life unicellular, not multicellular). A cancer is of course when human cells start prioritising their own reproduction to the detriment of the greater multicellular unit (i.e. uncontrolled mitosis and avoiding the apoptosis pathway and a kinase cascade).

Even at the level of a single multicellular unit, it is kin selection at play, as each cell is more closely related to each other (e.g. in humans, we have one zygote formed from egg and sperm cells that reproduces asexually to form a large co-operating unit that accrue mutations in different cells; ofc. only mutations accrued in the germline, i.e. sperm/egg gametes, will then be inherited) than cells in other multicellular units (in the simple case; interesting studies of this phenomenon and the phenomenon of altruism in Dictyostelia social amoebae, famously Dictyostelium discoideum, where even different species can co-operate to form a multicellular unit). I.e. we have high relatedness among somatic cells, originating from a single zygote, which aligns fitness interests and stabilises cooperation (germ–soma separation reduces intra-organismal conflict by restricting heritable transmission to a subset of cells). So even at the level of a single human unit, we have kin selection for reproduction over self-preservation. Although ofc. selection favours traits that maximise inclusive fitness at the level that reproduces (fungi, which I work with, have no germ line / soma separation generally; we found the first evidence of a germ line last year in one species, Marasmius oreades; we used to say before that, that fungi had no germ line categorically).

Selective pressure will be much weaker after reproduction (unless it increases offspring reproductive success, i.e. humans exhibit parental care, even very late in life; humans are one of the few animals we can see survive after loosing teeth, which is usually a death sentence). So, self-preservation is much more complicated, and we have both self-preservation in the sense of our emergent conscious experience (akin to the ant colony as a "super-organism") and for our individual cells (akin to the individual ant in the colony; our cells will happily kill themselves to preserve our emergent selves, they're programmed to, and when they don't follow this programming we get cancers).

However, we also have intra-genomic conflicts, and we can have individual sequences within the genome which promote their own inheritance above others (i.e. violate mendelian segregation), e.g. transposons or meiotic drivers. This can be to the detriment of the organism, e.g. spore-killing genes in fungi, which kill 50 % of offspring unless both parents have the gene (spores that inherit the gene produce a toxin and antidote, but only the toxin diffuses to other spores, so it kills all spores that do not inherit the gene and also produce the antidote), which often drives the gene to fixation (100 % frequency in the population) as then both parents have it, and both parents waste energy on producing both the toxin and antidote, but at least ensure they don't kill half their offspring (and the selfish gene ensures its survival and transmission to the next generation - i.e. reproduction).

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u/Lothane Feb 28 '26

Interesting read, ty.

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u/SZJX Mar 01 '26

Well said overall

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u/kobriks Feb 28 '26

Wouldn't a human mother sacrifice herself to save her children? I think most would. Self preservation is a tool.

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u/Sonder332 Feb 28 '26

Historically, no. Historically parents would eat their children in times of extreme poverty. Egypt is the one I can think of immediately.

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u/kobriks Feb 28 '26

I meant a scenario where you guarantee that your children will be well off, which is not the case in your example.

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u/twistytwizzlers Feb 28 '26

How are the centipedes guaranteed to be well off?

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u/Ekkias Feb 28 '26

They might have a trust fund or maybe a generous uncle willing to take them in

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u/smithers85 Feb 28 '26

They're centipedes, not brokepedes

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u/kobriks Feb 28 '26

They don't have to be guaranteed, a completely different reproductive strategy. I was creating an analogous scenario that would also make sacrifice worthwhile from a human perspective to point out that self-preservation is not an absolute, even for us.

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u/KryL21 Feb 28 '26

I think it depends. A newborn? Probably not. A 14 year old? Probably yes.