Gene Expression

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Photo credit: AP

In light of last week’s posts about why human evolution continues, I think it is critical to make concrete the reality of reproductive variance. It seems highly likely now that Jamie Lynn Spears is pregnant again. This might be a moot point if she has an abortion, though now that the word is out the public relations fall out might reduce the likelihood of that choice. The behaviors and outcomes of the lives of the Spears sisters are in the public spotlight, so let’s leverage this into an illustration of evolutionary theory. Last year I wrote Jamie Lynn Spears: it runs in the family?:

“I heard about it on the radio, they were talking about it. It’s real popular down there. Everybody knows about them,” Raynard Norman laughed. “It’s embarrassing, kind of. If it’s not her, it’s Britney, so at least it’s not Britney this time. But I’m not surprised, not really. … Nobody’s surprised because it’s not uncommon with her family. Next time, use a condom.”


Not uncommon in her family? Look, here is what we know: out of the 4 known pregnancies of the Spears daughters only 1 seems to have been planned. Britney has reported that it was not her wish to have another child with Kevin Federline, that it was a “mistake.” Unlike Britney Jamie Lynn’s first pregnancy was not expected, and now it looks it she’s pregnant again! What’s going on here?

It may be that the Spears’ daughters are very fecund for physiological reasons. Perhaps the likelihood of insemination and implantation during any given instance of sexual intercourse when they’re ovulating is just very high compared to the mean human female. If this tendency is heritable, then the Spears’ exhibit a high reproductive fitness in a society where the average woman is not even replacing themselves. That is, the proportion of genes which can be traced by descent to the Spears’ family in future generations is more likely than not to be higher than for those who do not exhibit such innate physiological fertility. This change in gene frequencies is evolution.

Of course there’s a simpler explanation for what’s going on here: the Spears’ are not good long term decision makers. These sorts of personality traits are often heritable, that is, some of the population level variation can be accounted for by gene level variation. This is obviously the Idiocracy thesis; anecdotally I’m sure you know from your own family experiences that the irresponsible siblings are more likely to breed while the responsible ones are more likely to put off becoming parents. I wouldn’t be surprised if the Spears’ case there’s relatively high time preference, and right now those with high time preference have a much higher fertility than those with low time preference, all things controlled. If Jamie Lynn’s daughter, Maddie Briann Aldridge, becomes pregnant before the birth of her second child we’ll know that this is an exceptional family….

Related: Do the less intelligent have more children? & Breeding the future.

Comments

  1. #1 John Emerson
    October 13, 2008

    Unless they fuck up in a big way the Spears girls are financially secure for the rest of their lives, and if they want to have a dozen illegitimate children each there’s no real problem with that. There’s nothing especially wrong with early childbearing if the parents can afford the children. Early childbearing was normal in eras when the wife stayed home and when it was possible to get a decent job without much education. But the Spears girls don’t need jobs any more. They’re not like us.

    Britney’s music is completely not to my taste, it embodies a lot of the stuff I hate about pop culture, and since she’s fronting for a high-tech music conglomerate her creative input is not great. Nonetheless, she’s worked hard as a performer and has outcompeted almost everyone in that biz. Prodigies of any kind often have emotional problems and problems socializing, and many skills require intensive training regimens starting as young as 6 — e.g., gymnasts and figure skaters. I’d put Britney in that class, and her sister too.

    One of the problems with American culture for me is that a lot of it (Britney, TV and cable news) is simultaneously technically virtuoso / state-of-the-art and utter horrible crap. The behind-the-scenes thing about making pop music or making the evening news show a technologically awesome process being used to make a harmful product.

  2. #2 razib
    October 13, 2008

    Unless they fuck up in a big way the Spears girls are financially secure for the rest of their lives

    that *unless* is a big qualification, at least in britney’s case. there was some concern during her “crazy” period that her spending was going to go through all her cash. 99.99% of people have no idea how you could burn through $100,000,000 in 10 years, but 99.999999999% don’t have that much money. but look at the celebrities who have to end up filing for bankruptcy after their income drops below their expected and habituated consumption….

  3. #3 Charles Iliya Krempeaux
    October 13, 2008

    @John Emerson, you said…

    “There’s nothing especially wrong with early childbearing if the parents can afford the children. Early childbearing was normal in eras when the wife stayed home and when it was possible to get a decent job without much education.”

    True… there nothing especially wrong with early childbearing.

    But (and I’m not necessarily talking about any of the Spears here) I suspect there’s a “difference” with someone who sleeps around and accidentally gets knocked up as a teenager… and someone who marries and intentionally has children in their 20’s or 30’s.

    I suspect that there is a difference in the nature of the selection going on.

    I suspect that there’s a trend that certain things tend to get selected for by women (and men) who sleep around and accidentally get pregnant. And that this likely has a genetic impact on the children who result from this.

    And I suspect that there’s a (different) trend that certain (other) things tend to get selected for by women (and men) who get married first and then get pregnant. And this too likely has a genetic impact on the children who result from this.

    (Note that I’m not trying to say one is “good” or is “bad”.)

    (And yeah, I know, I’m kind of agreeing, in a long winded-way, with what Razib said in the last paragraph of this post.)

  4. #4 John Emerson
    October 13, 2008

    Even bankrupt celebrities end up with a fair amount of money. The ones who actually end up destitute and homeless are mostly the mentally ill ones, and even they usually get bailed out.

  5. #5 Tod
    October 13, 2008

    Steve Jones says “as Darwin himself realised evolution’s third ingredient is isolation”. He discusses the results of sexual openness in mixing populations that have been largely distict until now. Could someone please explain why he thinks this significant and why he is wrong .

    Evolution selects phenotypes. Phenotypic variation will decrease as isolation does. What is wrong with this argument?

  6. #6 razib
    October 13, 2008

    Phenotypic variation will decrease as isolation does. What is wrong with this argument?< ?i>

    no, it won’t necessarily. in fact, admixture is liable to create new genotypic combinations which did not exist before, which give rise to new phenotypes. you and steve jones should both read principles of population genetics, you need to put numbers on to these parameters instead of dealing in vaguely qualitative generalities.

  7. #7 windy
    October 13, 2008

    Steve Jones says “as Darwin himself realised evolution’s third ingredient is isolation”. He discusses the results of sexual openness in mixing populations that have been largely distict until now. Could someone please explain why he thinks this significant and why he is wrong.

    Divergence in small isolated populations is one kind of evolution, not the only kind.

  8. #8 razib
    October 13, 2008

    steve jones’ assertions to some extent are so dumb in their generality and pomposity that you almost don’t want to respond. i know that some academics called up by the press didn’t want to say anything they thought the assertions were so ridiculous.

  9. #9 Tod
    October 14, 2008

    “some academics called up by the press didn’t want to say anything they thought the assertions were so ridiculous”

    You mean like

    “I respect Professor Jones but his statements are Ha Ha Ha Har no I’ll be all right, just give me a moment. OK I’ll start again, To say that evolution is coming to an end He He He He. Steve is quite wrong Ha Ha Ha Ha Ha Ha … no I can’t do it.

  10. #10 Tod
    October 14, 2008

    Thanks for taking the time to answer Windy, you read what I said but you knew what I meant.

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