Talk:Bateman's principle

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Contents 1 Controversy? 1.1 "Controversy" section removed from article 1.2 Exceptions list - proposed to replace "controversy" section 2 A Healthy Debate! 3 Who is Bateman? 4 "Examples of violations" section

[edit] Controversy?

To call Bateman's principle a controversy, or to consider Bateman's fly work as the only evidence in support is pretty nutbar. I havn't read Judson's 'Dr. Tatania' book, but I gather she was a Bill Hamilton student, and would be really surprised to hear that she describes Bateman's principle as controversial. In any case, I'd like to see references to the papers by "Some modern evolutionary biologists"...

I've moved deleted the section from the article and move it below. The last paragraph about DNA fingerprinting showing true monogamy to be rare is totally besides the point of Bateman's principle.

Pete.Hurd 07:10, 31 December 2005 (UTC)

Judson says in her book "Bateman's principle has a fundamental flaw: it's wrong." The chapter where she discusses it is posted as an online sample here.

Thanks for that link Lyrl, Judson means Bateman's principle to means that females have only the minimum amount of sex to insure fertilization, rather than definition used in the WP page: sex differences in initial parental investment producing sex differences in mating behaviour. Given her definition she's certainly right, I'm just not sold on her definition being what is usually meant by "Bateman's principle". I'll check a bunch of sources later on today and see what definition they use. Cheers, Pete.Hurd 19:28, 31 December 2005 (UTC)

I've modified the proposed section below. Hopefully it's more accurate/relevent now.Lyrl 15:54, 31 December 2005 (UTC)

She argues against the statments "a female's reproductive success is not increased by mating with more males" and "a male's reproductive success increases with each female he mates" (see modified section, below), both of which are quoted in the WP definition.

She also argues against the principle that "fertility is seldom likely to be limited by sperm production but rather by the number of inseminations or the number of females available to him" quoted in this article. This part isn't in the online sample, but she points to sea animals that do not mate, but rather emit sperm and eggs into the sea - each is equally unlikely to get fertilized because of the location issues. She also refers to flowers, where pollen delivery by pollinators is the limiting factor in reproduction. And then goes on to list a variety of animals where the male actually runs out of sperm - garter snakes, zebra finches, blue crabs, and rams (it apparently can take several days before they're capable of impregnanting a female again). And she then gives several examples of hermaphrodites where their mating behavoir indicates that sperm production is more expensive than egg production. She also supports this argument by saying females prefer to mate with virgin males (with presumably higher sperm counts)

This article also has a quote from Bateman "there is nearly always a combination of an undiscriminating eagerness in the males and a discriminating passivity in the females," where Judson spends an entire chapter of her book talking about female promiscuity, and sometimes males lacking 'undiscriminating eagerness.'Lyrl 23:46, 31 December 2005 (UTC)

Yes, there are many well-known exceptions to Bateman's principle, and it would be very useful to document these in the article. I think the quote above ought to be included in the article, with some of the discussion you have below about the "nearly always" part. Williams (1966) pointed out the sex-role reversed counter examples, such as pipefish (seahorses) phalaropes, etc. There's quite a literature on sperm limitation in orthopterans that's relevant. The Judson piece seems like a good place to start, at least in classifying counter-examples, eg, 1) sex role reversal, 2) sperm limitation examples, 3) etc... Off hand I can't say who discussed such things pre-Williams, but it would be really good to discuss all these if-ands-and-buts in a historical context, which ought to lead to Trivers' 1972 reworking of the concept into his parental investment theory. Cheers, Pete.Hurd 16:50, 1 January 2006 (UTC)

[edit] "Controversy" section removed from article

At least one evolutionary biologist believes Bateman's principle is often not correct. Olivia Judson argues that Bateman's conclusions were limited by such things as short observation time in his experiments.

Observation of many species, from rabbits to slippery dicks (a type of fish) to fruit flies, has shown that females have more children if they have sex with more males. This is in contradiction to Bateman's theory that "a female's reproductive success is not increased by mating with more males."

She also points to research in which males will guard one female and mate only with her, attempting to prevent her from mating with any other males. Examples include stick insects and Idaho ground squirrels. These observations seem to challenge Bateman's theory that "a male's reproductive success increases with each female he mates."

[edit] Exceptions list - proposed to replace "controversy" section

• The statements "a female's reproductive success is not increased by mating with more males" and "a male's reproductive success increases with each female he mates" are (sometimes? frequently?) false.

Judson is arguing against these statments, and so only gives counter-examples, of course. One of Judson's counter-examples is the fruit fly Bateman studied, so I'm not sure the older references are reliable anymore. Any suggestions for recent sources that gave supporting evidence for these statements? Or old sources that are felt to still be reliable?

• The assumption that females have a relatively larger investment in producing offspring can be false. In animals that spawn into the sea, for example, each sex's investment is approxamately equal. In animals with internal fertilization, many sperm must be produced for every egg - so even though it takes less energy to create one sperm than one egg, males of many species spend more energy making gametes than do females.

• The statement that the sex that invests the most in producing offspring will become a limiting resource is not always true. In flowers, for example, the female part of the flower invests more energy into making seeds than the male part of the flower does. The reproduction of (most?) flowing plants, however, is limited by delivery of the male gamete - pollen - not by production of the female gamete.

• Bateman's statement "there is nearly always a combination of an undiscriminating eagerness in the males and a discriminating passivity in the females" and his assumption that anisogamous species would be polygynous is false. [Many examples of female promiscuity]

That should be a start, at least. I'm not sure all the bullets fit under the category of 'exceptions', though; at least a couple of them seem to be arguing directly with Bateman's principle as it is defined in this article.Lyrl 22:56, 3 January 2006 (UTC)

[edit] A Healthy Debate!

Owing to numerous grammatical mistakes and a lack of clarity in the argument, it is difficult to divine exactly what the writer above takes exception to in the claim that there may be some problems with Bateman’s principle. Instead the author dismisses the notion that there is “controversy” over Bateman’s principle as “nutbar.” Yet even a cursory visit to the internet shows that there is considerable debate in the scientific community about Bateman’s propositions. One could look at Jonathan Knight’s article, “Sexual Stereotypes,” found in Nature (17 Jan 2002) or read through the range of papers delivered at a symposium entitled “Bateman’s Principles: Is it Time for Re-evaluation?” (University of Missouri, St. Louis) to understand that, in keeping with the scientific process, there is a vibrant and necessary debate on the various assertions and implications of Bateman’s principle. It is, we must remember, not a law. And in the normal course of scientific inquiry, we continue to test the hypotheses to see if they stand up to scrutiny now permitted by technological and scientific advances and the questioning of formerly unacknowledged social blinders.

It seems clear, at the very least, that some of the basic tenets of Bateman’s principle do not apply as widely or consistently in the natural world as was once believed. For reading on related topics, one should certainly enjoy the accessible and informed work, Dr. Tatiana’s Sex Advice to All Creation by Olivia Judson (evolutionary biologist, research fellow at Imperial College in London). But Judson is not alone. Joan Roughgarden, Professor of Biological Sciences at Stanford University, offers a wide-reaching analysis of sexual and gender diversity in Evolution’s Rainbow. Marlene Zuk, Professor of Biology at the University of California, Riverside, argues that gendered assumptions about human behavior has historically hindered our ability to accurately interpret animal behavior and cautions us against looking for models for humans in nature. These are just a few of the many works on the fascinating topic of evolution and the myriad sexual practices of the animal kingdom.

What there should be no controversy over is that Bateman’s principle is still in need of study, critique, and testing. The scientific community and the general public are benefited when there is an exchange of ideas and new information. Without this we would still be living in a flat world. I’m sure, Angus John Bateman, as a scientist, would expect no less.—Preceding unsigned comment added by Mmason2 (talk • contribs) 22:09, 2 January 2006

Like I said above, I think that it's uncontroversial that the sex that is a limiting factor will be a resource that the other competes over, while the rule that anisogamy leads to polygyny is not always true. The if ands and buts relating to the second have long been documented, and should be collected together by form of violation and discussed in the article. "Nutbar" wasn't constructive, my apologies. Whether "Bateman's principle" is used to mean a) "limiting sex is contested resource", or b) "anisogamy leads to polygyny" is something I'm still looking into. The most recent edition of Alcock's book (the only standard textbook I can find just now that mentions Bateman's principle) uses a). Other mentions that implied definition a, in my non-systematic search through my bookshelf, were Trivers' 1972, and Eric Charnov's "Sex Allocation". I didn't find any clear uses of the b form of the definition, but I seem to have loaned out most of the books I'd expect to find them in. Pete.Hurd 23:42, 2 January 2006 (UTC)

[edit] Who is Bateman?

For the general reader it would be beneficial if this article provided some background on who this Bateman character is(Angus John Bateman or A.J. Bateman.) Even a very brief "A.J. Bateman was a biologist who..." type sentence would be great. To throw around his last name as though everyone knows who he is is a disservice to the readers. Also some sort of pointer or reference to his 1948 paper that started it all would also be nice(I think it is Bateman, A. J. "Intrasexual Selection in Drosophila." Heredity, 2 1948, but I'm no expert here.)—Preceding unsigned comment added by 129.100.252.112 (talk) 16:14, 28 February 2006

[edit] "Examples of violations" section

The first paragraph in this section is misleading and requires more accurate wording. The author states "... to fruit flies, has shown that females have more children if they have sex with more males."

In humans, for example, it is not the number of males the female has sex with that determines whether they will have more children. Rather, it is the number of successful instances of procreative potential intercourse with a male (by "procreative potential intercourse" I mean that (1) the male is fertile; (2) the male engages in vaginal intercourse with the female and (3) the male ejaculates in the female's vagina during intercourse). Thus, a woman is just as likely to get pregnant on a given day if she has vaginal intercourse with 5 different male partners or vaginal intercourse 5 times with a single partner.

The second paragraph is interesting and (perhaps) --Njals Saga 01:32, 23 September 2007 (UTC) relevant. However, I believe the author places too much weight on this being a "challenge" to Bateman's theory via the use of only two examples. If we substitute published studies for species, I believe that most scientists would want to see more than two contradictory or null studies before making such a claim. For the vast majority of the animal kingdom, there is little doubt that the more instances of male sex with new females will increase that male's probability of genetic offspring.

I believe the main article would be improved by "tightening up" the wording in the second paragraph above. I prefer the phrase "procreative potential intercourse" but am open to other terms. The whole issue of number of partners versus number of times one male had intercourse is an important distinction for the overall evaluation of Bateman's ideas.--Njals Saga 01:26, 23 September 2007 (UTC)

Males emit fewer and fewer sperm with each act of closely-spaced intercourse. Females are more likely to get pregnant if they have sex with multiple "fully charged" males than if they have sex with one male multiple times (receiving fewer and fewer sperm with each successive act).

The second paragraph gives only selected examples from Judson's book, and her book offers only a few such descriptions from the files she says she has that are "bursting" with such examples. I don't think this article is trying to prove or disprove the theory within the article, it's only reporting on what respected scientists such as Judson are claiming. The two examples are just that, examples of what Judson is basing her argument on, not the entire foundation of her claims.

If each female only has sex with one male, then the more females a male mates with the more likely he is to have genetic offspring. If females mate with multiple males (as occurs in the large majority of species), then sperm competition comes into play. By going off to mate with other females, the male leaves his original partner available to other males, who may provide sperm that outcompetes his original deposit. In many species, the cost of sperm competition is so high that males are more successful in fathering offspring if they stay around just one female and concentrate on preventing her from having sex with other males. Lyrl^Talk _C 00:25, 24 September 2007 (UTC)