Is "gender selection" instinctual population control?

[OKIsItJustMe]

Here's an interesting story:
http://www.jpost.com/servlet/Satellite?cid=1233304677912&pagename=JPost%2FJPArticle%2FShowFull

Feb 4, 2009 8:32 | Updated Feb 4, 2009 8:45

Females turn into males when times get tough... on the sea floor, that is

By JUDY SIEGEL
Without intending to provide ammunition for the current argument over whether a woman would be as competent as a man in the prime minister's hot seat, Tel Aviv University scientists have found that when times get tough, nature sends in the boys - at least when it comes to an important species of coral.

TAU zoology Prof. Yossi Loya is the first in the world to discover that Japanese sea corals engage in "sex switching" under periods of stress, especially when threatened by global warming, The Jerusalem Post has learned. The fragile, flower-like sea animals are essential to all life in the ocean.

In times of stress such as extreme hot spells, the female mushroom coral (known as a fungiid coral) switches its sex so that most of the population becomes male.

The advantage of doing so, says the world-renowned coral reef researcher, is that male corals can more readily cope with stress when resources are limited.

…

In both China and India, without any policy specifically calling for fewer female children "culture" has led to a higher percentage of males.

On this map, "… Blue represents more women, red more men than the world average of 1.01 males/female."



On the other hand, humans seem biologically primed to do the opposite. When times get tough, women have more girls:
http://www.medicalnewstoday.com/articles/105013.php

Baby's Gender Linked To Mother's Diet At Conception

Article Date: 23 Apr 2008 - 3:00 PDT

New research from the UK suggests that a baby's sex is linked to his or her mother's diet around the time of conception and the finding may explain why fewer boys are born nowadays in the industrialized world, including the UK and the US.

…

The researchers found a strong link between the consumption of a high energy diet around the time of conception and giving birth to sons.

Over the last four decades the birth rate for boys has been declining steadily in industrialized countries including the UK, the US and Canada. The decline is small but consistent, at around one in 1,000 births a year, said the researchers.

…

The results showed that:

• 56 per cent of the women in the highest energy intake group had sons.
• This compared with only 45 per cent of the women in the lowest energy intake group.
• Women who had sons not only had higher energy diets but they were also more likely to have eaten a wider range and higher amount of nutrients such as potassium, calcium, plus vitamins C, E and B12.
• There was also a strong association between eating breakfast cereals and having sons.

…

Stress During Pregnancy Determines the Gender of the Baby

Saturday, September 22, 2007 at 2:38:28 PM

…

During the study, the researchers gathered information on stress levels of the mothers of more than 6,000 babies at the start of their pregnancies. The data was gathered on the basis of the women’s sleep quality, confidence and ability to cope with everyday tasks.

…

It was found that women who were stressed during pregnancy were five per cent more likely to have girls as compared to those deemed relaxed, reports the Daily Mail.

The newspaper report suggests that women in Western nations, including the UK, generally give birth to more boys than girls, with 105 boys typically born for every 100 girls.

Previous research has shown that number of boys being born goes down following major political and social upheaval.

…

It seems like biologically, our species wants more children during times of hardship. It makes sense from a competitive standpoint, but may not work well when the cause of the hardship is overpopulation. This is what makes me wonder about female infanticide…

[anonymous171]

1. "me wonder about female infanticide."

What?

[OKIsItJustMe]

2. One way for families to have more boy babies is to kill (or abort) girl babies

http://en.wikipedia.org/wiki/Sex-selective_abortion_and_infanticide

[muriel_volestrangler]

4. I think the point is: what is there to 'wonder' about female infanticide?

It's wrong. Why does this study do anything to make you 'wonder' whether that's true?

[TheWraith]

5. I think he's saying he wonders whether it's driven partially by unconscious instincts. nt

[OKIsItJustMe]

6. What I wonder is whether it is an instinctual conterbalance to the biological stress response

Don't you think that it's a striking coincidence, that in the two most heavily http://en.wikipedia.org/wiki/List_of_countries_by_population">populated countries in the world—between them, they account for more than ⅓ of the world's population—parents are killing their female babies?

I'm not advocating infanticide (or abortion) as a means of population control, however, in general, I think we have too little appreciation for how "instinct" governs our behavior. When I see "irrational" behavior, I sometimes look for "instinct" to explain it.

http://discovermagazine.com/1996/sep/firstkillthebabi864
http://www-personal.umich.edu/~phyl/anthro/infant.html

Despite what I learned in science class, even mice seem to have instinctual population control. (Eliminate predation, give them unlimited food and adequate space, a mouse colony will first swell, as you would expect, and then decline.)

[muriel_volestrangler]

7. If it was 'instinctual', then it would be biological too

and would be counter-productive, since it works against the ratio of pregnancies.

No, I think it is a sexist act, that tries to modify the social decisions of the Chinese government, or the decisions of the Indians families themselves of how many children to have. It's not 'irrational'; it's based on sexism. They know what they're doing, and have worked it out using reason. They, and large parts of their society, still give men more power than women, and so they value male babies more than girls.

[OKIsItJustMe]

9. Check out the links I provided

They talk about reasons for infanticide in other animals (including primates):
http://dss.ucsd.edu/~jmoore/publications/DensityInfanticide.html

…

The first example comes from the work of John Calhoun on captive rats (Rattus norvegicus, Osborne-Mendel strain). He created high-density populations in which aggression, infanticide, and infant neglect became rampant; these findings were reported in an influential Scientific American article entitled "Population density and social pathology" (1962a). Previously unreported patterns in the data, discussed below, indicate that at least some of the supposedly maladaptive behavior made good adaptive sense.

The second example is that of infanticide among langur monkeys (Presbytis entellus). In this case, the killing of infants by male langurs has been interpreted by some as pathological (resulting from high population density) and others as adaptive (evolved via sexual selection); proponents of the adaptive interpretation have cited the absence of a correlation between population density and infanticide as a fatal flaw in the pathology hypothesis (see Hrdy et al., 1995 and Sussman et al., 1995). However, they have had difficulty explaining intersite variation in the expression of infanticide, a problem cited by proponents of the pathology hypothesis. These conflicting interpretations are to considerable degree resolved by application of an economic defendability model, which explicitly rejects the underlying hypothesis of both camps that population density should exert linear effects on behavior.

The behavioral variation observed in these cases, which has been described as pathological by some and strategic by others, may be neither; both of those terms suggest that the behavior is somehow "located" within the individual--that is, the individual is maladjusted, or the behavior is "genetically specified" in some detail within the individual's genome (e.g., Hausfater, 1984). This may be a misleading way to view both situations. Instead, these apparently complex regularities in behavior can be derived from the interaction of a few simple tendencies (e.g., hostility toward strange males) with predictable demographic settings, rather than requiring specified mental rules or modules (cf. Altmann & Altmann, 1979). Particular sociodemographic settings reliably can lead to behavioral outcomes which are adaptive and thus seem "genetic" because of the consistency with which they appear, without in fact being genetically specified per se (Elman et al., 1996; Hill, 1999).

Both of these classic examples deal with the supposedly negative effects of high population density upon animals. Interest in the evils of crowding exploded during the mid- to late-1960s, in a climate conditioned by group selection theory, the 'population bomb', and a dawning awareness of ecological disaster looming ahead. The University of California's on-line library catalog (MELVYL) lists two books with subject heading "crowding" published between 1960 and 1970; between 1970 and 1980, there are 38. During the early 1970s, population density was seen as threatening our very existence (as illustrated oxymoronically by the epigram above). This interest soon collapsed (only 7 books since 1990), in part because it became clear that crowding per se did not automatically lead to pathological behavior (Freedman, 1975). While population density seemed intuitively related to criminal behavior in humans and agonism in nonhumans, the relationship was neither deterministic nor systematic and so population density, as an explanatory variable, fell out of favor.

…

[muriel_volestrangler]

15. In your 3 links, there's only one reference to killing one sex of baby rather than another

and that is from the first (the Discover magazine one):

such instances as do occur among humans can only be explained as a result of a particular cultural bias (favoring male babies over females, say) or of individual pathology.

And that's what I'm saying. This is cultural bias (and it's sexist), not instinctual.

[OKIsItJustMe]

17. You say it's not instinctual

However, you must admit:

• It's a very effective strategy for decreasing population growth.
• While it is not practiced in all cultures, it is practiced in multiple cultures.

These are among the reasons why I think it may be.

Like I said, I don't advocate the practice. If I haven't been explicit enough, I find it abhorrent.

I also find the murder of adults abhorrent, yet I think you'll agree it is instinctual. (Or perhaps we have different understandings of "instinct.")

http://dx.doi.org/10.1006/tpbi.1994.1027

Copyright © 1994 Academic Press, Inc. All rights reserved.
Regular Article

Gene-Culture Coevolution and Sex-Ratios: The Effects of Infanticide, Sex-Selective Abortion, Sex Selection, and Sex-Biased Parental Investment on the Evolution of Sex Ratios

Kumm J., Laland K. N. and Feldman M. W.

Stanford Univ, Dept Biol Sci, Stanford, CA 94305, USA and Univ Calif Berkeley, Dept Integrat Biol, Berkeley, CA 94720, USA

…

[muriel_volestrangler]

20. It may be an effective strategy to reduce population growth

But that in no way makes it instinctive. From your abstract:

The evolutionary consequences of culturally transmitted practices that cause differential mortality between the sexes, thereby distorting the sex ratio (e.g., female infanticide and sex-selective abortion), are explored

My emphasis - culturally transmitted. As I say in #19 below, you don't expect to see anything instinctive that reduces population in the long term - that goes against natural selection. And the fact that it is not practised in all cultures makes me think more that's it's a cultural thins, rather than an instinctive one.

[OKIsItJustMe]

10. (it's not instinct) "it is a sexist act"

What makes you think that sexism is not instinctual?

---

FWIW: Have you read The Good Earth? It's not a scientific study. It's not a true story.

In any case, in the midst of a famine, a couple with 3 children has a fourth child (a girl) who the mother strangles at birth (there isn't enough food to feed their family with only 3 children.) Buck (a feminist herself) based her book on her experiences in China (and the sexism she saw there.)

It's a powerful scene. The mother "O-lan" is portrayed by Buck as a strong character, who does what needs to be done.

[kristopher]

14. Can you support your certainty?

The evidence says you are wrong (see anthropologist Marvin Harris writings on the subject) in dismissing OK's question. What you might consider is the question of "what, exactly, is the basis of "sexism"?"

All of the symptoms you list can be attributed to resource availability, reproductive pressure and the way cultural/social institutions form to deal with those recurring problems.

[muriel_volestrangler]

16. Why would resource availability and reproductive pressure make killing girls a good move?

Having an excess of boys, in times of shortage, means more mouths to feed as children, but won't increase the ability of the group to have any more children in future years. Killing boys in times of shortage, however, would preserve the ability of the group to reproduce. And the change in the ratio of boys and girls born to mothers with high or low calorie diets supports this. To say that it makes sense for one biological tendency (the 'instinct' to kill some girls at birth that OK is hypothesising) to oppose another biological tendency (the birth ratio of more girls to boys for lower calorie diets) seems completely illogical to me.

[kristopher]

18. The "group" rarely needs to "preserve the ability to reproduce"

The much more common problem that "groups" have to overcome is population exceeding the carrying capacity of the land. This has been true since the earliest hunter gatherer cultures.
Again, if you are really interested, get a copy of Cannibals and Kings by anthropologist Marvin Harris from the library.

[muriel_volestrangler]

19. No, natural selection is all about preserving the ability to reproduce

It's pretty much the definition. So anything instinctive (that is, inherited) should act to preserve or increase the population, in the long term.

Cultures are another matter. They are taught, and modified by reasoning and social interaction.

To be clear, I don't think that any ethnic group of humans have 'instincts' that other don't.

[kristopher]

21. You don't know what you are talking about.

[muriel_volestrangler]

22. A devastating repsonse! Well played, sir

Go ahead, explain how a trait involving killing your own offspring is going to get propagated by genes. For bonus points, explain why killing males would become an instinctive behaviour when the science shows that the balance of sexes shifts towards females when calories are scarce. How are opposing tendencies both meant to benefit the survival of the species?

Just saying 'it does', or "you don't know what you are talking about", is pointless.

[kristopher]

23. I gave you a reference

And the reference gives a complete argument. You are attempting to deduce an extremely complex set of circumstance from very limited knowledge and intuition. The fact that I don't want to dedicate several hours to writing something that has already been written well only means that I don't waste my time for your whims. If you actually gave a shit, you'd have already checked the reference.

[muriel_volestrangler]

24. I've already looked at a summary of that book

and it seems to be mainly about culture. It has a theory about earlier menarche as diet changes. I can't see anything about male or female infanticide in the summary; telling someone to get hold of a book (if I buy it, it'll take a couple of weeks at best; if I try to get it through an inter-library loan, it'll be months), without saying what its argument is, is hardly a productive way of carrying on a discussion (I note that every time a link has been given so far in this thread, they've turned out to either have nothing to say on the subject, or to support my position). You could try summarising what it has to say about male and/or female infanticide, and how it is instinctive, rather than cultural.

[kristopher]

25. And you could read the book.

I don't mean that in a snarky way, but some things just require effort, and this is one.

[muriel_volestrangler]

26. You promise me that it has a proper argument about female infanticide being instinctive?

And not cultural? Even if it does, I wonder how valid the argument is, given the research indicating the bias towards female births in low calorie situations that the OP notes, which seems to be a recent discovery.

[kristopher]

27. It might lead to a re-evaluation

of the picture you hold of a schism between instinct and culture. It may reveal a structure incorporating them both that you aren't yet aware of.

[kristopher]

28. Questions about methods of OP study

Cereal-induced gender selection? Most likely a multiple testing false positive

The recent paper by Mathews et al. (2008) with a
provocati ve t i tl e ‘ You are what your mother eats’
generated a lot of attention in the press and over 50 000
Google hits putting forth the genetically implausible claim
that women who eat breakfast cereal are more likely to
have a boy child. Their result is easily explained as chance.
We will not go into other methodological issues such as
recall bias and measurement errors, difficulty in measuring
cumulative exposures in nutritional data, unmeasured
confounders, variable categorization, statistical power and
study design, as Pocock et al. (2004) recently reviewed the
sad state of obser vational studies and Ioannidis (2005)
reports that 80 per cent of obser vational studies fail to
replicate or the initial effects are much smaller on retest.
An implausible claim should strongly overcome chance as
an explanation even to be considered. We focus on chance
as the cause of their finding....

<snip>

...In our first analysis, we computed 264 t-tests and plotted
the resulting ordered p-values versus the integers giving a
p-value plot, Schweder & Spjøtvoll (1982); figure 1. Some
explanation: suppose we statistically test 10 questions
where nothing is going on. By chance alone we expect the
smallest p-value to be rather small. We actually expect the
p-values to be nicely spread out uniformly over the interval
0–1. Except for sampling variability, we expect that the
ordered p-values plotted against the integers, 1, 2, ., 10,
to line up along a 45-degree line. With this dataset, we
have 264 p-values and the plot of the ordered p-values
against the integers, 1, 2, ., 264 is essentially linear. This
plot implies that the small observed p-values, indeed all of
the p-values, are simply the result of chance and not due to
any effect of the food items...

http://journals.royalsociety.org/content/u12p544020045241/?p=279feacf2ce84e448d2107ca544834aa&pi=24

[OKIsItJustMe]

29. "Natural selection is all about preserving the ability to reproduce"

What about http://www.google.com/search?q=evolution+altruism">altruism?

[wtmusic]

3. Relax and eat Wheaties if you want a boy?

Wow. Pretty amazing stuff.

[XemaSab]

8. Most sea creatures reproduce by spewing their gametes into the open sea

Additionally, human males can theoretically father thousands of children.

If there's an "instinct" towards producing male children, it has to do with the possibility of having your genes seeded far and wide.

[OKIsItJustMe]

11. One human male can (theoretically) father thousands of children—if HUNDREDS of women help

One woman cannot mother thousands of children, regardless of how many men try to assist her.

[GreenPartyVoter]

12. I wanted a girl. Is this suggesting that taking prenatal vitamins before conceiving

made it more likely that I would have boys? (Which I did.)

[OKIsItJustMe]

13. You may have increased the odds by a few percentage points

Or, so the studies suggest.