A nice fishy example

God clearly does not love all fetuses.  Ones particularly expendable are fishy ones.  The male three-spined stickleback is the fish in question right now.  He goes in for cannibalism and recent research confirms an explanation:

The researchers manipulated the clutches that individual males cared for, replacing up to 100 percent of the eggs fertilized by the male with eggs fertilized by another male. They found that the higher the percentage of “alien” eggs, the more likely the male was to completely cannibalize the clutch. The researchers suggest that the fish probably take their cues from the odor of the developing eggs as the paternal genes start to kick in.

Cannibalism of a clutch with a high proportion of alien eggs makes sense for the fish, because it avoids putting a lot of energy into producing offspring that carry another fish’s genes, and because by eating the eggs it gets energy to rear future clutches of its own eggs.

But what I like about the example for teaching  is that it’s a clear case where the explanation appeals to the good of the agent without giving any reason the agent actually could entertain.  As we say in evo-speak, it would be much too expensive and impractical  to build a  fish brain that could grasp facts about passing on one’s genes.  So evolution has linked his actions with odor or taste.  Others’ eggs are just so yummy. 

It’s also a really good way into  to the apparently mythical idea that step fathers tend to kill their step children, though if I’m out of date on the many twists and turns of that debate, please someone let me know.

18 thoughts on “A nice fishy example

  1. I just googled “stepfather, murder” to see if I can get some recent news about the state of the debate. Interestingly, the news seems to be about their being murdered by stepsons.

  2. Feminist Philosophers favorite Kanazawa:

    “Infants and children who do not live with two biological parents face 40 to 100 times as great a chance of being injured or killed within the family as those who live with both biological parents.”

    I think he may be referring to studies by evo-psychologists Martin Daly and Margo Wilson.

  3. Actually, most child abuse is perpetrated by the not-biologically-related-to-the-child boyfriend (or sometimes husband) of the child’s mother. The kid is not his, is in the way, cries, doesn’t obey, takes up the attention of the mother, interferes with his life, etc. And without the biologic tie to temper the impatience, frustration and rage…… However, usually the child is not eaten , but merely punched, stomped, thrown at the wall, plunged into scalding water (that will make it stop crying for sure), hurled down the stairs….. I have seen way too many of these cases.

  4. Mythical? Where did you get this idea?

    And D&W’s hypothesis has nothing to do with the biological phenomenon described here. For D&W, increased risk in step family (death, negligence, violence) is a by-product of the cues that trigger paternal love.

  5. JJ, that was APPARENTLY mythical, right? An intentional oxymoron used to denote irony?

  6. Xena, nothing as clever as that.

    Rob, useful references – thank you.

    J & EM – what I’ve seen does suggest that the worst are boyfriends, and I think that might make us suspicious of at least one form of the evolutionary explanation – that is, the version that appeals to the commitment involved in permanent partnerships and the idea that that time and effort is wasted on children with no genetic link.

    The Daly and Wilson 1994 article –
    does include the wasted investment argument and extremely high figures from Canadian and British data. That data has been challenged on the grounds that it incorporates a recording bias. I see they’ve responded to that challenge, and I’m not sure where that debate stands.

    Some studies seem to find live-in non-biologically related males a significant threat to children, but at least one other challenges this. There’s also some suggestions in some studies that marriage and commitment actually lessen the death rate, and boyfriends do seem more lethal.

    I’m going to have to think about how I’d modify my earlier comments.

  7. I wasn’t sure how complicated the debate had become. I did study some research on non-human primates killing new mothers’ infants for the sake of spreading their own genes, and the links to child abuse in human families. But those classes were a brief part of a larger overview of primate behaviour that I studied years ago.

    Thought I’d let you clarify before I commented, JJ. I agree with J as well.

    And what planet is that Kanazawa guy living on, anyway? Battered women stay because makeup sex after violence is better, and they believe violence is love. But, unfortunately AGAIN, my source is in a textbook in my storage locker. Does anybody remember the social psych experiment (I think the researchers were with Stanford in the1980’s?) where researchers and participants checked each other out at the top of a high rickety bridge on a windy day? There were a huge number of “yes I’ll date you” responses, compared to the control group, who flirted on the ground.

    I’ve also seen a milder form of this adrenaline-junkie behaviour in young men who intentionally check out other women in front of their girlfriends, just to watch them get riled. I wouldn’t be so bold as to try to back that statement up with a source, though. I think the soap opera relationship commentary came from a fashion magazine.

  8. xena: some midwifery theory i’ve read suggests that the ‘love at first sight’ thing that some mothers have upon the birth of their child is a hormone rush caused by the uber-frightening/painfulness of childbirth. seems interestingly similar to this flirting on a bridge thing.

  9. Maybe, elp. I’m far from an expert on human love&bonding. I’ve been single for the 8 years since my son was diagnosed, because of all the scary statistics about remarriage and filicide.

    But the hormone rush in childbirth sounds plausible. Mother bear urges make sense in a context of evolutionary psychology.

  10. elp, what an interesting connection you’ve made.

    I think the hormone is oxytocin; I’m worried at the thought that pain is required, because it would mean that all the pain-free births don’t set it off. E.g., well-done ceasarians. But perhaps indeed it happens that way.

    Oxytocin is supposed to cause trust in humans, and perhaps the bonding done in threatening situations is a matter of feeling trust and so on. If so, one definitely wants to be around people who can help! When the going gets bad, think of hanging out with engineers?

  11. Right, the contraction&lactation hormone. Present in post-o glow as well. Maybe this is too much information, but I took in a stray kitten a few years ago, as cute as U Has Betrayed My Tiny Trust on LOL Cats. I was literally lactating for the critter. No, I did not want to be the animal’s wet nurse, but some weird biological thingie happened. Poor thing was trapped in a construction lot.

    That happens sometimes, right?

    Does the oxytocin rush also kick in for some women when they fight with their lovers?

  12. >> One of the effects of the hormone oxytocin is that it triggers labour pains. It also strengthens the emotional bond between a mother and her new-born child. Oxytocin is released on a large scale during an orgasm, too. This neuropeptide is also associated with feelings such as love and trust. <<

    Hormone spray improves male sensitivity

  13. I wonder if there are little containers one could take to conferences.

    I can imagine the encounter with airport security. And now, errr..Ms jj, could you tell us why you are carrying this?

    Ah, well, you see my field is quite male dominated … .

    O, forget it!

  14. lol indeed.

    isn’t ‘florence nightengale syndrome’ something like this as well? (is it the one where you fall in love with your nurse? that’s the one i mean…) pain/fright–>love.

    jj, re your earlier, that midwifery reader (denis walsh) i wrote about a few months ago does think that epidural births get in the way of early bonding for exactly the reason you spell out. he’s concerned with it, because he suspects that the ‘love at first sight’ helps to make the first few weeks with teeny baby more bearable. seems plausible. but i would hope that no one would claim, based on this, that there’s something *wrong* w pain relief. i mean, surely the richest and most fulfilling relationships in our lives develop over time: they’re not ‘love at first sight’. why should the mother-child bond be different?

  15. >> i mean, surely the richest and most fulfilling relationships in our lives develop over time: they’re not ‘love at first sight’. why should the mother-child bond be different? <<

    I would sooner trust my "adaptive unconscious" (or whatever you want to call it) to do the choosing for me of potentially most fulfilling relationships than my clumsy, massively error-prone, conscious perception, which I suspect is more likely to focus on superficial saliences in others, like mere avowed opinions or the appearance of compatibility predicated on them. Maybe we would enjoy a greater diversity of relationships — diversity at the level of consciously-held opinions, beliefs, political views, etc. — if we found ways to rely more on our animal affinities rather than on the shallow overlay of consciousness, which experimental psychology seems to show, time and again, is so often so misleading, and fatefully so.

  16. I came back here to cross check something from a later post, and I just re-read Rob’s last comment. What a lovely sentiment. My hormone levels must be doing something to my head right now, because I’m half wondering if Rob is single.

    Animal Affinities?!? MEOW!!

    I think it’s time for a nice cool shower ;-)

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