Talk:Twin
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triplets
I think that somebody with the know-how and ability should re-edit this line for readability: twin "Historically, triplets have been quite rare and more than triplets so rare as to be almost unheard of" it occurs at the bottom of the article. I would my self but i dont really have the time or confidence in asertaining what was to be said by this sentence. viva wikipedia!
- Apparently, the article has been edited to resolve this readability issue; however, there are a number of ambiguities and what appears to be a math error. First, both twin pregnancies and twin births are mentioned, but the term "twinning" is not unambiguously defined as either twin pregnanices or twin births. Moreover, it's not clear whether twinning, conceptually, includes higher order pregnancies or births. Ex: "The rate of twinning varies greatly among ethnic group..."
- Second, The statement that "In 2001, for the first time ever in the US, the twinning rate exceeded 3 percent of all births. Thus, over 6% of children born in the US in 2001 were twins." is itself ambiguous because of the first point and does not follow logically or mathematically. If the twinning rate was exactly 6%, then the percentage of twins in the resulting population would be 6/103, or about 5.8%. Since we only know that the rate exceeded 3%, we don't know the percentage of twins in the resulting populations and it doesn't follow logically that it must be above 6%. In any case, extrapolation of the percentage of twins in the population is irrelevant. The reasons for the increase in the twinning rate *is* relevant but is unforunately not discussed. Someone with more expertise should resolve this or else the statement should be deleted.
- Third, The use of the term "ethnic group"[sic] to describe the Yoruba AND the inhabitants of a "tiny Brazillian village" is suspect. A brief google search also yielded contradictory information regarding populations with remarkably high twinning rates. "Distinct populations" might be a better choice. Ex: [1] (http://www.nature.com/cgi-taf/google_referrer.taf?article_product_code=NATURE&fulltext_filename=/nature/journal/v394/n6693/full/394533a0_fs.html&_UserReference=C0A804EF4651979CAC6970B58BD93F784A27)
- Fourth, "...research is underway to improve the odds of twinning,..." This should be changed to "increase the likelihood" or "increase the frequency". Unless we're talking about horses... ;-)
- I also took care of a typo and one tortured phrase. The article overall was great - lots of good information.
Disappearing twins
According to a special documentary on twins I saw on PBS, twin pregnancy is the norm, though twin birth is not. Due to advance in medical imaging technology and early prenatal care, doctors are detecting twins in the womb in early stage of most pregnancies. However, one of the twins disappear in most cases. The program didn't elaborate on what that finding means.
My intepretation is that, like most mammals, human pregnancy starts with one fertilized egg splitted into multiple identical copies to increase survivability of the species. However, the human womb normally eliminates the "extras" when one of the fetus is developed successfully. So the birth of twins are accidents where the womb fails to eliminate the spares.
I am interested to see some quote of medical researchs that confirm or deny this. Any Wikipedians know this area well?
67.117.82.5 22:51, 29 Sep 2003 (UTC)
The movie My big fat Greek wedding has a reference to this phenominon, the mother of the bride said that she found a cyst under her armpit and they found teeth and bones of her twin inside the cyst.
67.117.82.5 22:55, 29 Sep 2003 (UTC)
Actually, it was the aunt of the bride, and the "lump" was in her shoulder. JHCC
twins run in the family
"It is thought that identical twins do not run in families, but rather identical twins occur more or less randomly, however two sets of identical twins - two girls and two boys - were born on the same day to Geana Morris at the Lankenau Hospital in Pennsylvania, herself a fraternal twin, after she was implanted with two embryos during IVF in January 2004."
This has just been added and, tbh, has confused me. I don't see how that example is any proof of twins running in the family. After a lot of thought I've come to think that dizygotic twinning cannot be influenced by the father (he doesn't have control over the number of eggs released by the woman) and thus the chances of non-identical twins cannot be passed down from the father whereas monozygotic theortically can. For the mother monozygotic twins may be hereditary and so might dizygotic. However, releasing multiple eggs (for dizygotic) and releasing a single egg which devides into two foetuses (monozygotic, and is it foetii?) don't, it seems to me, to have a link. I've not read up on this anywhere and it's purely speculation but my point is that the example seems to be proof of nothing but a single instance of coincidence. Futhermore the process of IVF is known to boost the chances of twins (or more) because of the methods employed. violet/riga 00:22, 15 Aug 2004 (UTC)
- Well, as I understand it, the first part is right, identical twins are thought to be random on the basis of studies (and there is a proven genetic component in the incidence of non-identical twins). And your thoughts are about right - identical twins arise from spontaneous splitting of a fertilised egg, which is thought to be pretty random, whereas non-identical twins arise from releasing multiple eggs, and this seems to run in families (presuambly there is an inherited hormonal component). And, of course, IVF produces lots of (mostly non-identical) multiples because more than one fertilised egg is usually implanted. I have no idea whether there is an increased incidence of identical twinning with IVF, though.
- The recent case is just anecdote and doesn't prove anything, other than long odds will come up from time to time. It should be deleted, IMHO. -- ALoan (Talk) 00:48, 15 Aug 2004 (UTC)
- I added this item (which, btw, isn't 'anecdotal' as that is friend-of-a-friend-but-mot-provable rather than confirmed news report!) and the point, so far as I could see, was that each implanted egg became a pair of identical twins, (ie. not just two non-identical twins because of the dual implanting) and that the mother was a twin herself. The "It is thought that ..." which is anecdotal (without proof); this is a data point suggesting the reverse. --[[User:VampWillow|VampWillow]] 11:51, 15 Aug 2004 (UTC)
- Sorry but I still don't see how it adds to the article, being nothing more than a coincidence or perhaps a side effect from the IVF treatment. In fact, the whole idea of it being random determines that it is possible to have such an occurance and it doesn't necessarily mean anything. violet/riga 12:14, 15 Aug 2004 (UTC)
- Sorry, I didn't mean anecdote in the sense of unverifiable friend-of-friend, urban legend, sense but rather the scientific sense of anecdotal evidence: I saw the news story too, but a one-off event seldom tells you very much and certainly doesn't falsify the claim that identical twins occur at random. The passage starting "it is thought that" in the article is based on scientific studies, but recognises that the studies could be wrong (for example, there could be a small genetic component what the studies could not detect). I'm sorry, but I agree with violet/riga. -- ALoan (Talk) 10:28, 16 Aug 2004 (UTC)
- That one case is just anecdotal evidence, it does not indicate anything. Some sources said identical twinning is 1 in 300. Having two sets of identical twins is then 1 in 90,000 by simple arithmetics. One may argue the odd of having quad naturally is low. However, if the pregnacy is by IVF, then the odd is changed to 100%. It is like the odd of collecting a million dollar when the winning ticket is already in your hand. It is called conditional probability. Through IVF, multiple birth is almost guaranteed 100%. The only odds need to be considered are these multiple births turn out to be identical. In this particular case, the odd was 1 in 90,000 assuming the 1 in 300 odd is accurate. It is easier than winning a lotto. So to me, this example was no big deal. If these quads were all natural, then it is another story.
- Releasing multiple eggs per month by the mother is easily hereditory as proven by statistics, fraternal twins do indeed run in a family. Identical twins are less likely to be hereditory because having the zygote to split in two can be a very random thing. Or may be not. The body chemistry of the mother may play a part in the splitting of the zygote too. Who knows until some scientist research into this. Body chemistry can be hereditory. Modern prenatal care allows doctors to observe the early stage of pregnancy earlier than history had ever allowed. Modern findings proved that twin pregnancy is more common than people were aware of. The extra embryo is often rejected by the mother and singleton birth is resulted at the end (look up the topic on disappearing twins). Such finding also implies that how much the mother's body rejects a twin pregnancy due to hostile body chemistry can be hereditory. So even for what started out as random, genetics can possibly play a part in the final outcome. All these theories are all unproven. Scientists may see new evidences if they try to research along such possibilities. Kowloonese 22:54, 21 Oct 2004 (UTC)
Other kinds of twins; Twin-parent mess
Can there be half-sibling twins? These twins would have different fathers. They can be either faternal or semi-identical. I guess you can deliberately cause this with artifical insemenation techniques, but what about natural occurances?
I've seen this pheonemon in a soap opera, but a former co-worker who was once a nurse told me about a (supposed) real case too. In the latter case, the two fathers had different ethnicities, so the occurance was apparent.
On a different note... what if the two fathers were identical twins to each other?! Then the kids would be conventionally half-siblings and half-cousins, but genetically full-siblings! Or what if someone's dad's identical twin brother hooks up with their mom's identical twin sister? Then that person's (double) cousin is also his/her sibling genetics-wise!
--69.37.220.12 20:46, 21 Oct 2004 (UTC)
- You can throw incest in the mix and you can really make a mess. :-) Kowloonese 23:04, 21 Oct 2004 (UTC)
Genetic similarity
About genetic similarity, the article states there is a 246 probability to optain a geneticaly identical human offsprings (not being twins) from the same parents is a very basic assumption. If we consider the crossing-over occuring between the chomosoms during meiosis, this probability decreases greatly since material from the maternal and paternal chromosomes may "switch places" during the meiosis producing the gametes of the parents. Therefore, the statement in the article assumes that there was no crossing-over neither in the first nor the second offspring. This should be precisely mentionned or the probability should be revised cossidering this fact.
Edit (9 Mar 2005): has been corrected
--astrowob 04:04, 7 Feb 2005 (UTC)
Maybe we're all a little lucky
My friends are mixed sex twins not kidding. The guy is ok. The girl seems to be normal and healthy.
- It's possible that they aren't actually identical (I assume that's what you were talking about). Fraternal twins (like any other siblings) can end up looking remarkably similar. The only way to tell for certain is through DNA testing, which is expensive (or at least it was when I was born...), so a lot of parents don't have it done. -Aranel ("Sarah") 14:56, 25 Feb 2005 (UTC)
Twins as babies in Hollywood films
Is it just me or or is it most movies with babies as part of the cast are ALWAYS PLAYED BY TWINS?
- This has to do with child labor laws. You can only legally have a young child "working" a certain number of hours of the day, much less than with adults, so having two gives you more time to work with. With babies, I suspect that it's also a practical concern, since you can't necessarily depend on them being in the right mood to perform! -Aranel ("Sarah") 23:24, 28 Feb 2005 (UTC)
Semi-identical twins
Several [2] (http://forums.twinstore.com/eve/ubb.x/a/tpc/f/96860409/m/63410983511) sources [3] (http://www.madsci.org/posts/archives/2004-05/1085534032.Ge.r.html) on the 'Net state that semi-identical twins are a myth. I also found a site that looks like the contents of this article had been lifted from there, but can't find it again and in any case it's likely to be the other way round... the phenomena returns some 160 google hits, by the way. -- Kizor 08:46, 19 Mar 2005 (UTC)
Article needs material on twins in tricky crimes.
Someone please write a paragraph about criminality and penal code with regards to twins. E.g. if CCTV footage shows a person committing murder while lying in wait, and he/she is one of identical twins and they refuse to confess, do both of them get sent to the gas chamber? Issues like this are very popular in crime fiction stories and movies. Also, there was a recent news story about brazilian twins, who both sat in prison for drug trafficking, but one got released instead of the other due to tricking and bribe. He got caught and now both will have to serve some extra years for obstructing the way of justice.
Identical twins not the same gender?
The article has this line:
- Monozygotic twins are genetically identical unless there has been a mutation in development; they are only usually, but not necessarily, the same gender.
Could someone provide a refrence for this, it seems rather unbealievable, or seems like somethign that would require a very specific mutation in one of the twins, and thus exceedingly rare. If true, it needs more of an explination than the simple statment given. When such a thign happens are there other medical considerations? How rare is it? Is it even common enough to be called out in the article without saying that it is exceedingly rare? Dalf | Talk 18:22, 16 May 2005 (UTC)
- Oops the next paragraph addresses this. Dalf | Talk 18:23, 16 May 2005 (UTC)
- read Intersexual 4.250.198.126 19:00, 16 May 2005 (UTC)
- Oops the next paragraph addresses this. Dalf | Talk 18:23, 16 May 2005 (UTC)
I dramtically reduced the amount of text on identical twins not the same gender and removed the section header. It's not a relevant risk of having twins, and so its a nonsequiteur to spend an entire section and two paragraph on the phenomenon. From the sources I've seen, only 3 cases have ever been documented (not "3 in 100,000" or "3 in 1 million" or "3 in 2.5 billion" but just "3". Ever.) To put that into context, you have a greater chance of personally meeting and then going skydiving with conjoined twins than of having different-gendered monozygotic multiples. I do belatedly agree with Violetriga that the Intersexual article isn't directly on point -- I left that in in my initial edit to try to provide context for the description of the mono-multiple gendered process that I felt didn't belong here. I'd be open to putting in a wikilink to a different article that provides that context, but it really doesn't belong here. Any suggestions for where to link to? Nandesuka 10:48, 17 May 2005 (UTC)
- Well, identical twin and identical twins redirect here: how about Mixed sex identical twins? -- ALoan (Talk) 11:41, 17 May 2005 (UTC)
- That makes a lot of sense to me. We could even take the text I elided regarding XY / XO chromosomes and turn that into the stub of that article. Violetriga, is that OK with you? Do we have consensus? -- Nandesuka 14:02, 17 May 2005 (UTC)
- Sorry about the belated response - for some reason I hadn't noticed this discussion. I think the information should certainly be somewhere and I'm not entirely sure that it is worthy of its own stub, hence my preference for inclusion here. If you want to try it and see how well it works then by all means go for it - it may work well. violet/riga (t) 09:49, 2 Jun 2005 (UTC)
