Contraception and Causality; r/K Selection and Population Growth


Christopher Carr

Christopher Carr does stuff and writes about stuff.

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28 Responses

  1. Avatar Matty says:

    Brilliant, it honestly never occurred to me to apply r/K to human history I suppose because I’m used to thinking of reproductive traits as changing over evolutionary time but once you remember how flexible humans can be this makes a lot of sense.


    • Avatar Christopher Carr in reply to Matty says:

      Thanks, Matty. I think r/K as it’s often applied means that we classify one species as r and another species as K, but I know r/K is used as a descriptive tool for describing the growth of primate populations over time and in anthropology, so, given the fact that r or K will be dominant strategies under different sets of circumstances, it makes sense that human populations will adapt quickly to one paradigm or the other, or the kind of hybrid you see in countries like China or the United States where there are relatively large wealth disparities.Report

  2. Avatar James Hanley says:

    Nice post, Chris.  I’d like to see you do a follow-up one where you tie this into a critique of Garret Hardin’s “Tragedy of the Commons” article, in which he claims that voluntary reduction in child-bearing is ultimately self-defeating because those who do will select their type out of the population through lack of progeny, while the breeders will replace them with their many progeny.  It seems to me Hardin either ignores r/K selection theory or implicitly assumes that there will always be “r”  types in the human population, who will simply replace K types (if the latter get too Kish).  It’s an idea that’s been rolling around in my head for a number of years now, and I’d love to see someone tackle it.Report

  3. Avatar BlaiseP says:

    Educational attainment is a very critical factor in accounting for lifetime fertility differentials. Women with 1 or more years of college have sharply lower lifetime fertility than less educated women, regardless of race or Hispanic origin. Women with college degrees can be expected to complete their childbearing with 1.6-2.0 children each; 1.7 for non-Hispanic white, 1.6 for non-Hispanic black, and 2.0 for Hispanic women. For women with less education the total expected number of children are: 3.2 children for those with 0-8 years of education; 2.3 children for those with 9-11 years of education and 2.7 for high school graduates.

    Among unmarried mothers age 25 and older only nine percent had college degrees; about a third has less than a high school education. Birth rates for college-educated unmarried women are substantially below the rates for less-educated unmarried women.Report

    • Avatar Will H. in reply to BlaiseP says:

      This isn’t the first time that you’ve brought that up. I find it a convincing argument, but I wonder if that’s just because it seems to coincide with my own notions. I tell myself that I like it because it’s based on data– hard numbers– and that’s what I like rather than it just being a comfortable position– but that’s also what makes me suspicious of it.
      Data does weird things at times.
      So, I’m wondering if there is anything that would show that the results stated are due to educational effect or the natural effect of aging from having acquired the education?
      That is, if we teach them in 10 years what they would otherwise learn in 12, would that make any difference?Report

      • Avatar BlaiseP in reply to Will H. says:

        I made a better argument, now lost to the Database Error Beast, which went along these lines:

        Education is not Culture.   The educated are taught to think for themselves.   It is the uneducated who must resort to external cultural cues for guidance.   As the uneducated grow to maturity, they learn to impose those cultural cues upon others.   Religions used to manage this stunt until the rise of the Enlightenment and its priorities were centered on the Individual.

        Notice how Education is associated with Liberal thought.  As it turns out, the farther up the educational ladder we look, politically, there seems to be a rough parity between conservatism and liberalism, but the Ivory Tower itself is an exceedingly liberal edifice.   The educated might imbue the cultural norms of the Ivory Tower upon each other in the faculty lounge but there’s not much real estate there and most of those fights are petty attempts to impose some goofy bit of pilpul on each other.Report

        • Avatar Will H. in reply to BlaiseP says:

          I had a better reply that was just lost to the same Database Error.
          Briefly, a reserve of resources means very little outside of the psychological effect if one is without the means to exploit them. So, I don’t see something like “culture” or “wealth” as being specific enough to be of any value (in current terms).
          I was wondering about the ideas I’ve heard floated about for restructuring high school education, to offer vocational training in lieu of the latter years of high school.
          If it’s simply a matter of maturity gained, then keeping them in school for X number of years would do well.
          If we actually have to teach them something, that could make a bit of a difference.
          From what I gather (and I could be wrong here), it looks like you’re making an argument toward the use of peer pressure.Report

    • Avatar Jeff in reply to BlaiseP says:

      That might be significant except:

      Some speculate that it is “culture” that causes fewer children as a function of wealth, but this is a meaningless explanation. Attributing rising or declining birth rates to culture fails to explain why the phenomenon is so widespread and cross-cultural: as populations have access to more resources, as their needs progress up Maslow’s hierarchy, they produce fewer offspring, whether those populations are American yuppies, middle-class Japanese or Koreans, members of the European upper class, chimpanzees, elephants, or penguins, despite having access to more resources.

      If the r/K graph holds true for all the above, it’s hard to see how education could be a cause.Report

      • Avatar Christopher Carr in reply to Jeff says:

        Unless a high level of education is strongly correlated with wealth.Report

        • Avatar BlaiseP in reply to Christopher Carr says:

          I cannot see how it would be otherwise:  that education doesn’t correlate with wealth would be a singularly odd proposition.   Education changes value systems.Report

          • Avatar Christopher Carr in reply to BlaiseP says:

            My point exactly.Report

            • Avatar BlaiseP in reply to Christopher Carr says:

              Well, do the uneducated become wealthy?   Not usually.   I did some work many years ago on the sociology of Communism in various locations throughout the world.

              The state of Kerala began to return Communists to India’s parliament in the 1950s, much to the consternation of some folks in my chain of command.   The people grew rice on terraces and had a communal labour system which lifted water from one paddy to the next, all the way up the side of the mountain.  Their culture was thus well-suited to the framework of communism without the usual totalitarian tendencies seen elsewhere:  the rice paddy had inured them to a notion of the commons in ways few other cultures ever exhibited.

              We looked at another culture, that of China, where the One Child Policy caused untold heartbreak and misery.   Curiously, Kerala’s birth rate fell faster than China’s.   What could be the difference?

              Literacy and the education of girls are central tenets of Communism.   China only educated its girl children to the sixth grade, when most of them left school.   But Kerala educated its girl children for 12 years, often more.

              Though Kerala has morphed into a thoroughgoing capitalistic culture, the ancient frameworks of the common good and plentiful education have not budged, even a little.   I’ve been to Kerala, it’s an amazing stew of cultures, idealistic yet intensely practical.   Do check out that link I’ve provided, Chris.Report

    • Avatar Michelle in reply to BlaiseP says:

      @Blaise–I think you’re on to something. Around the turn of the twentieth century, there was great concern among nativists about falling reproduction rates among more educated, middle and upper class women (nativists also expressed great concern about immigrant and lower-class women out-reproducing white women). Some of these folks argued that educating women caused blood to flow toward the brain and away from the reproductive organs, thus greatly reducing their fertility. They therefore recommended curtailing any kind of higher education for middle-class women as a means of saving white civilization.

      I’m almost surprised that this argument hasn’t resurfaced among some of the right-wing save-the-family types.Report

      • Avatar Kimmi in reply to Michelle says:

        it has, but primarily as a “once you’re XYZ age, you get married and have a lot of kids”

        … with the corrollary that if you “happen” to get pregnant at one of our thinly disguised places designed to create atmosphere where that will happen, you just get married and it all turns out fine.Report

      • Avatar BlaiseP in reply to Michelle says:

        Heh heh!  I had never heard that physiological explanation.    It has been my fate in life to put two women through college and higher education, a process I’ve thoroughly enjoyed in both cases.   The first woman got a double major undergrad degree and two master’s degrees out of the process, the current woman in my life is well on her way to becoming my partner in software.

        At a strictly selfish and cynical level, what sort of man would prefer an uneducated woman in his life?   Wouldn’t it promote his status to have the love of an educated woman?    Wouldn’t it be embarrassing if you were a caveman and your wife evolved… but you didn’t?Report

        • Avatar Michelle in reply to BlaiseP says:

          Well, that argument didn’t exactly stem the tide of women heading to college. The number of women getting a college education has steadily increased to the point that they now outnumber men.Report

          • Avatar BlaiseP in reply to Michelle says:

            The children of these educated women become educated themselves.   The larger-brained species don’t have many offspring but they’re cared for in ways smaller-brained species don’t care for their offspring.   They mature later as well.   Educated women lavish attention upon their children in ways uneducated women don’t, or can’t.    The advertisers tell us the most desirable population is the adult woman, not only because she’s often out-earning her husband but because she’s spending his money on the household.Report

  4. Avatar Katherine says:

    Very interesting post, and the logic seems to hold together.  I’ve never though of applying r/k selection in that way, as biologically humans are defined as an r-selecting species relative to other animals (we have a few kids and care for them rather than having dozens, hundreds or thousands and not carving for them), but it still works.

    What I find interesting in the chart is that it presumes no change in third-word birthrates over the next 40 years, which strikes me as unlikely.  Birthrates are already starting to decline everywhere outside of Africa.Report

  5. Avatar Citizen says:

    Interesting Chris,

    There is one parameter I typically find missing in the topic of slow decline of the white population.

    What if the white traits aren’t recessive?

    In the populations of non whites and the mixing of the races, typically what is observed is the skin color lightening, and the hair and eye color eventually becomes lighter.

    Historians often try to trace white traits back to small populations. If there were so few from the start, why are there so many today?  I have observed typically any american family is only one or two generations from producing a white child.

    When all the colors bleed into one, what will be the reality, not the pre-conceived notion?

    Guess the “Whiting” of America isn’t as popular a headline.

    Fighting over resources is nothing new to humanity, even in small populations with vast resources, there were many disputes.Report

    • Avatar Matty in reply to Citizen says:

      I was so taken with the cleverness of linking ecological theory and social change I missed a question.

      What is it that is declining, that is what is the definition of white anyway? Is it based on ancestry, specific biological traits (which ones) or a ‘know it when I see it’ basis?


      • Avatar Christopher Carr in reply to Matty says:

        Here is a fairly interesting article on the topic:

        Originally, “white” was a very restrictive term that essentially meant Western European. Many Eastern Europeans were considered a separate racial category. Gradually, the meaning of the term began to expand and reached near its broadest application around the time of Father Connell.

        Citizen is right that the term’s use as a racial category is rather arbitrary. Let’s take our President for instance. We consider him “black”, but only one of his parents was of African descent. So, to be correct, he would be half black, half white genetically. Culturally-speaking, Barack Obama was raised by his mother and Indonesian step-father, so there we might presume he is half white, half Indonesian culturally. Yet, he is universally considered “black”. Don’t tell me this isn’t some modern iteration of the one-drop rule.Report

        • Avatar Matty in reply to Christopher Carr says:

          Originally, “white” was a very restrictive term that essentially meant Western European. Many Eastern Europeans were considered a separate racial category.

          Hell I seem to remember reading 19th Century (?) polemics on the differences between whites and Irish.Report

        • Avatar Brandon Berg in reply to Christopher Carr says:

          It’s not really a one-drop rule so much as a bias. Colloquially, we classify most half-African, half-European people as black, in part because many of the traits associated with European ancestry are recessive. But if someone looks white, we typically don’t consider him to be black, even if we know that his great-grandfather was black.Report

  6. Avatar Citizen says:

    There is no white. A quick ancestry exercise makes most people sober up:

    Take a blank page, a “I” in the middle of the page, below that put two “ll”, for your biological parents, below that place 4 “llll”

    Continue this for a mere 12 generations. No man is truly an island. No race is even remotely pure. Whether we like it or not, we are deeply rooted in the foundations of all humanity.

    The inversion of this very flattened ancestry pyramid, the children of today may or may not reproduce, leads to a less flattened pyramid going into the future. Possibly columns.Report

    • Avatar Brandon Berg in reply to Citizen says:

      Of course there’s white. It’s what we call a person who expresses most of the physical traits associated with European ancestry. This correlates strongly with actual European ancestry.Report

  7. Avatar mnemos says:

    Interesting, but I have a question…  I understand some of the logic of the r/K description, but the intention is always how to meet or exceed replacement.   For humans in the current technological situation, replacement is about 2.1.  For many of the populations discussed the fertility rate is well below 2.1 – from Singapore at 0.8 to Italy and Japan at 1.4.  The United States is close to replacement at 2.06  on one list, but most of Europe is not.  How does the logic make sense when fertility is well below replacement?