Talk:Sexual dimorphism

Thanks for restoring this article. I have added a few examples off the top of my head to be helpful to anyone who checks this article for information. I will add more information later.

Patrick0Moran 15:40, 13 Aug 2003 (UTC)

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I'm concerned about the following bit.

(In grammatically gender-sensititve languages, the grammatical gender of the animal species name besides humans indicates the larger gender of that species. Therefore, the animal species name is grammatically feminine if the female is larger than the male, and vice versa.)

This seems to be too broad. I can think of half a dozen counterexamples in Spanish and Italian off the top of my head. Furthermore it doesn't have much to do with the main thrust of the article. Unless anyone comments, I'll remove it. Theanthrope 20:54, Dec 18, 2004 (UTC)

(In grammatically gender-sensititve languages, the grammatical gender of the animal species name besides humans indicates the larger gender of that species. Therefore, the animal species name is grammatically feminine if the female is larger than the male, and vice versa.) I agree, it's simply irrelevant to the biological article unless it were a fairly reliable guide to relative animal sizes and I agree with you it probably isnt. We'll park the statement here if the original author wants to defend it.alteripse 21:45, 18 Dec 2004 (UTC)

I have to agree here. The wording of the phrase indicates that it's an "always" condition. But considering that "the Cat" = "die Katze" (German, female) = "el Gato" (Spanish, masculine) indicates that it's entirely unreliable. Of course, there's also the fact that much more reliable in German is that the grammatical gender of the species is determined upon the general size of the animal, rather than any sexual dimorphism in the animal. Thus, larger animals are masculine, while smaller animals are feminine. Of course, "larger" and "smaller" here is intentionally vague and subjective, and this "rule" is still by no means reliable enough to use it for anything except where only a wild guess is the other choice. --Puellanivis 18:27, 17 August 2006 (UTC)

The wording of the caption for the picture of the pheasants should be changed to reduce redundancy. I think “large degree of sexual dimorphism between the sexes” should be changed to something like “large degree of sexual dimorphism” or “dramatic difference in form between the sexes”. —Chris Capoccia 18:11, Jun 24, 2005 (UTC)

Good suggestion - done! -- ChrisO 18:17, 24 Jun 2005 (UTC)

I think one would have to be socially retarded to not realize that the human on the left is male and the human on the right is female. Sour pickle 04:58, 7 November 2005 (UTC)

Maybe so. But the drawing, frankly, isn't that good, and I pity the alien that has to make an identification based upon it. - Nunh-huh 05:02, 7 November 2005 (UTC)

Firstly, there's social dimorphism represented in the picture with hair length. Men and women do not naturally have differing hair length. The drawing could be made better by giving them equal hair length, and the male a beard. But even in this case, there are women who must shave or they will grow a beard (any woman exposed to enough testosterone will grow a beard, as evidenced in transsexuals), and men can readily grow breasts under the effects of hormones (again, transsexuals can demonstrate this easily.) But take away even intentional hormone manipulation, there are men who develop breasts (which can be quite large) naturally, it's called Gynecomastia, and there are women who must shave naturally to remove facial hair.

To be entirely accurate, sexual dimorphism in humans is very much strictly limited to resulting from hormonal differences, and to a degree much higher than any other species, there is a very low sexual dimorphism. Of course, the key point that you say is "one would have to be socially retarded", which *does* happen. The gender cues that we interpret are very much not at all accurate indicators of true sex at all. Super models are taller than the average man, and there are 10% of men that are shorter than the average female. Many crossdressers can easily demonstrate that it is possible to fool the vast majority of people's sexual indicators, and be regarded or considered as the other gender.

Basically, what I'm saying is, don't take a picture that exagerates the differences as an indicator of sexual dimorphism. Take any two pheasants of differing sex and you will readily be able to tell them apart. The same cannot be done with humans. There are a number of androgenous males and females, that can make sexual distinction difficult. To reiterate, that doesn't happen at all with strongly sexually dimorphic animals. --Puellanivis 18:27, 17 August 2006 (UTC)

I'm surprised there isn't a picture of a black widow spider male and female in this article. --AnYoNe! 22:18, 22 January 2007 (UTC)

Your talking about all humans. What I have seen in some races is sexual dimorphism that is extremely pronounced. Indian men in the north of India are much larger and heavier than Indian women. Show me a population of Indian women that are 6'. Most of them are only 5' and slender. So what I'm saying is that sexual dimorphism in humans varies between races.

Human sexual dimorphism

"Homo sapiens has a high level of sexual dimorphism in general." "The low level of sexual dimorphism in humans is said to correlate to the human species' high degree of paternal investment." Methinks this is hard to grok. So what is it? "High level" or "low level"? I have definitely read both views. I think Britannica says social mammals (like humans) generally have high levels of sexual dimorphism, including behavioural dimorphism. I'm a bit suss about the parental investment argument tho, 'cause it's almost circular -- if one parent invests more, voila!, you got sexual dimorphic behaviour already! Can anyone give me a source for each opinion? Then I can go check 'em and make up my own mind. Live long and prosper. V Alastair Haines 11:35, 29 March 2007 (UTC)

I don't think high/low in this case is something that can be untimately defined, but it is competely dependent upon what it is compared to. Mikael Häggström 10:49, 15 July 2007 (UTC)

I've found a good source on this now. Evolutionary psychologists have done a lot of work on human mate selection including cross-cultural studies of expressed preferences. Paternal investment over evolutionary time should predict current male preferences regarding ideal age of mates. If human males have had low investment, they will have prefered relatively older women (who will look after offspring without them). If investment has been higher, the preference will have been for relatively younger women. The source suggests if the offspring (men now) prefer women in early 20s, it would suggest higher levels of polygyny and higher sexual dimorphism; if men now prefer women in mid teens, this would suggest higher monogamy and lower sexual dimorphism. LOL, that's a rock and a hard place! The source wisely doesn't take sides, just comments opinions are divided. There's a lot more to the analysis than I've mentioned here, and there are literally hundreds of studies. Alastair Haines (talk) 05:16, 17 April 2008 (UTC)

I think the part, that women can withstand cold better then men becouse of more subcutaneous fat should be removed until someone has found a good source for that. Maybe the better insulation is only a compensation, because women baturally have a slimmer body, which leads to a higher surface/volume ratio, which increases the ratio between lost thermal energy and body weight. --Qaywsxedc (talk) 17:48, 21 June 2008 (UTC)

Either the definition of sexual dimorphism at the top of the article is incorrect, or (much more likely I believe) many if not most of the examples mentioned in the Human sexual dimorphism section (gonadal, hormonal differences, etc) are not really sexual dimorphism. Here's one source... http://www.blackwellpublishing.com/ridley/a-z/Sexual_dimorphism.asp that defines sex. dimorph. as "existence of physical differences between the sexes, other than differences in the sex organs." That definition doesn't specify "external" like the current wikipedia does. I would think that external *is* be important if the term is used primarily with regard to Darwinian sexual selection (i.e., I prefer the definition at the top of the page here, although I'm not an expert.) Is anyone (perhaps with more credential than me on the topic) up for hacking out the stuff that doesn't fit. I think this would also help with the "high" vs. "low" dimorphism question below, settling it on the low side if I'm correct. sbump (talk) 17:55, 6 June 2010 (UTC)

What's the problem with evolution?

Under the header Uncertainty, the following is found:

in birds larger size of males is explained by preference in the struggle for female and larger size of females—by advantage of laying large eggs. But it is unclear why in the first case no large eggs and in the second no struggle for female are needed.

What is unclear? Both the male and the female are larger than they would have been if it wasn't for the factors mentioned. The difference in size is simply the difference in to which DEGREE the factors are essential. Read The Origin of Species and you'll see that traits are advantageous in a relative sense and not an absolute one, as if there were a standard size which either the male or female deviated from. Mikael Häggström 10:54, 15 July 2007 (UTC)

This section is so confused and contradictory that I've taken it out altogether. The deleted text is pasted here:

Uncertainty

Treating the general phenomenon of sexual dimorphism as a consequence of narrow mechanism of sexual selection created many problems. It was hard to explain sexual dimorphism for characters, which with great difficulty can be related to sexual selection (e.g., leaf number and shape, branching pattern in plants). Interpretation of the same phenomenon needed different logics. For example, in birds larger size of males is explained by preference in the struggle for female and larger size of females—by advantage of laying large eggs. But it is unclear why in the first case no large eggs and in the second no struggle for female are needed. It is still difficult for the theory to explain large size of females in some mammals (bats, rabbits, flying squirrels, spotted hyenas, dwarf mongooses, some whales and seals), existence of marked sexual dimorphism in monogamic species with sex ratio 1:1, and the dependence of sexual dimorphism on the reproductive structure of the population.

I suspect it's either derived from a general lack of understanding of the whole preceding section, or from Creationist dogma, or perhaps both. I can make neither head nor tail of it in scientific terms, as it deals with issues which are really not controversial.--Richard New Forest 14:57, 29 October 2007 (UTC)

There's more than one ideology opposed a priori to biological explanation of sexual dimorphism. Thanks for cleaning things up. Alastair Haines 00:10, 30 October 2007 (UTC)

Textbook like

This headings like "examples", "explaination" etc are textbooklike. But encyclopedia is about "presenting facts", not "teach subject". See WP:NOT. Thanks. Meets are hoped (talk) 06:28, 10 December 2007 (UTC)

There're five images in the article(without counting the one about human's sexual dimorphism) 4 of birds and one of fishes, wouldn't it be okey to add one of insects or mammals, I think we have enough of birds. —Preceding unsigned comment added by 189.175.172.15 (talk) 04:15, 15 April 2008 (UTC)

Thanks for comments, feel free to improve the article by rewording or rephrasing ideas. Even better, add in material from books you have access to. If others disagree with you it may disappear, that's just how it works. But it's fair, and most changes, most of the time, mostly lead to improvement and agreement.

As a postgrad, Encyclopedias of Philosophy, Theology, Language, History and many subjects are my textbooks. Sometimes they are the fastest way to get simple explanation or a quick set of examples that I'd have to take ages finding elsewhere. Some of them cover all examples and provide comprehensive explanation. I didn't see Wiki is not a textbook on the Wiki-is-not list, but I only scanned a big page.

I think this article has a long way to go. It needs way more content, a lot more organization and some improvement in style. Any steps in that direction are welcome, anyone can do it, no one is paid to do it, so it won't happen unless people just get in there and do it. Go for it! Become an expert as you read sources and write them in your own words or quote them into the article.

Same goes for pictures. If you own a picture and are willing to donate it, or if you are willing to locate public domain pictures, go for it! Please, please, please. And, speaking just for me, birds are nice, but yeah, I'd like to see a bit more diversity in the graphics. Mind you, dimorphism is the subject isn't it, so we are really looking for pictures of a male and a female with visible differences, frequently (mostly) it's all under the skin or in the head. ;)

Happy hunting! ;) Alastair Haines (talk) 11:02, 29 April 2008 (UTC)

explanations for sexual dimorphism

Curiously this article is blocked at my university (can't have us biology postgraduates reading any article about sex), but checking this for the first time outside of uni I notice that it is missing niche separation as a cause of sexual dimorphism. At least in birds it is the more important cause of size differences. [1] for an example (lots more come up on on google scholar). Sabine's Sunbird talk 20:08, 14 July 2008 (UTC)

That's also getting on my nerves. There's a lot of focus on passerines and game bird sex dimorphism, but very little on the fairly dramatic dimorphism birds of prey have. Falcons often have size skewed towards females, with many being a 1/3 larger than their mates. Generally, it's more so that females can take larger prey and the males smaller so that one prey group isn't too heavily hunted. That section could really use expansion, and be less general. —Preceding unsigned comment added by 71.239.162.195 (talk) 04:37, 7 February 2010 (UTC)

Sexual size dimorphism

I noticed this more specific article a couple of days ago, but is there really any need for it? This article isn't excessively long, and SSD is excessively short. It has some potential, but it has been poorly integrated into the network of articles - for example this article should obviously link to it (probably using summary style) and it should link back here (which it doesn't). Unless there is so much on SSD that it makes this article too long or biased towards size differences, I think the best option is to merge it here. Richard001 (talk) 22:28, 8 October 2008 (UTC)

Yes – can't see how we could justify a separate article at present. Richard New Forest (talk) 08:38, 9 October 2008 (UTC)

The article's author hasn't been editing for over a year, so we can't really get any comment from that quarter. There isn't much to incorporate, though we should include the term 'sexual size dimorphism' and the abbreviation in the article somewhere. A pity the article has no references for the other statements, though I guess they could be added as well. Richard001 (talk) 07:20, 10 October 2008 (UTC)

Sexual dimorphism in humans

Men are 34% stronger in the lower body. Source: http://www.ncbi.nlm.nih.gov/pubmed/8477683 Someone please correct it. --- dnx-x1 —Preceding unsigned comment added by Dnx-x1 (talk • contribs) 21:44, 12 November 2008 (UTC)

In a control group of 8 men and 8 women. How robust. —Preceding unsigned comment added by Akaner (talk • contribs) 17:20, 13 October 2009 (UTC)

Yes, correct it to reflect how males have been having a free ride the whole time. Natural truth isn't allowed to interfere with academic knowledge. —Preceding unsigned comment added by 74.13.44.121 (talk) 05:11, 31 August 2010 (UTC)

Text in the anglerfish picture

It says that the male anglerfish is a parsite. The definition of parasite:Parasite states that the victim has only harm, but in this case, the "victim" has unlimited amounts of semen for the eggs. Therefore, the male anglerfish isn't a parsite, they're living in symbiosis. Someone correct the picture and reupp it. —Preceding unsigned comment added by 213.250.11.107 (talk) 15:28, 17 August 2009 (UTC)

Handicap

"the proposed evolutionary force" is totally overstated. Though popular, the handicap principle (actually, "handicap hypothesis" is becoming more popular among scientists in recent years) seems to apply in far fewer cases than generally assumed. For peacocks, I think it has never been proven (given they are Phasianidae, among which some sort of ornamental plumage is widespread, an "unhandicapped" male would have zero fitness!). As typical of mid-20th century ethology, this is just another "intuitive" explanation with meager empirical support.

There are probably almost as many causes as there are different sorts of sexual dimporphism, dichromatism, size dimorphism etc. Reverse size dimorphism in predatory birds is simply competition-avoidance (this has been extensively proven). Dysmorodrepanis (talk) 00:54, 29 October 2009 (UTC)

I've rewritten the evolution section to present what textbooks seem to say. Evercat (talk) 19:44, 21 January 2010 (UTC)

New study finds "Sexual Dimorphism" between heterosexuals and homosexuals.

From the article: Pheromonal studies also have added to the scientific knowledge of sexuality, according to Dr. Goldstein. "Sex-atypical connections were found among homosexual participants. Amygdala connectivity differences were found to be statistically significant and provided evidence towards sexual dimorphism between heterosexual and homosexual subjects. " I am confused by this usage of the phrase "sexual dimorphism". Does this suggest that the meaning can be extended to members of the same gender who have different sexual preferences? If so, should wikipedia reflect that? 97.94.199.170 (talk) 16:04, 4 June 2011 (UTC)

Race and Sexual dimorphism

I'm concerned about including the anecdotes of someone who specializes in insects on human sexual dimorphism. As there really isn't a genetic basis for the differentiation of race, the unsubstantiated comments in the "Race and sexual dimorphism" section come off more as hearsay than actual fact. It contains outdated terminology, and half of the section gets its information from the opinions of an unqualified expert. I think the section should just be deleted. — Preceding unsigned comment added by 99.191.40.174 (talk) 09:10, 15 September 2011 (UTC)

That does not explain why you removed the citation to Ashley Montagu who taught anthropology at Princeton University. The citation was cited to a reliable source -- an expert speaking within his field of study. --Ephert (talk) 09:16, 15 September 2011 (UTC)

sexual dimorphism is a very understood part of living creatures differences. Yet in human evolvement of the thinking mind it becomes less inclined to provide basic evaluations of whats to be concrete and unquestionable while human thought has provided outlets to creative dimorphism within intellectual creativity and human inclinations.Maybe earlier hominids were more in tune to earthly survivals through instinctual strenght. While modern mans social and earth shattering thinking mind has reigned dominance.Is the crossbreeding of humans with differing skin color or facial details a change from mono polydimorphism within a group that maintains its genetic pool and suddenly that new divergence now extends gene pool diversity within the offspring.Since homo sapiens sapiens are all thinking oriented people regardless of the genetic variances within our appearances due to our inheriting the genes from our parents now creating a new gene pool of traits passed from each others ancestors. Are all humans evolved from a common ancestor or from divergent ones that have survived but evolved to distinguish the gene pool we have. Basically the human mind trancends the simple mental state of their nature that primitive man or woman encompassed but with a strong will to survive. — Preceding unsigned comment added by Nabjeski (talk • contribs) 00:42, 27 October 2011 (UTC)

'American English'? 'British English'? Some other language?

"Dichromatism is where a sex of a given species is more than one color including that of saturated, vibrant hues."

For the life of me I can't work out what the author of that sentence was trying to convey. Also, it (Dichromatism) seems to have no logical connection to the preceding sentences, the paragraph, or the article.

Aaah. Such is Wikipedia... — Preceding unsigned comment added by 86.160.209.12 (talk) 20:42, 15 December 2011 (UTC)