# Is it possible to be born "backwards," lateral-symmetry-wise? **URL:** \ **Category:** Factual Questions\ **Created:** [February 4, 2010, 3:16pm UTC](https://boards.straightdope.com/t/is-it-possible-to-be-born-backwards-lateral-symmetry-wise/527674 "2010-02-04T15:16:42Z")\ **Posts on this page:** 14\ **Page:** 2
**Author:** ![Shagnasty](https://avatars.discourse-cdn.com/v4/letter/s/9dc877/32.png) [@Shagnasty](https://boards.straightdope.com/u/Shagnasty)\ **Post date:** [February 5, 2010, 1:07am UTC](https://boards.straightdope.com/t/is-it-possible-to-be-born-backwards-lateral-symmetry-wise/527674/21 "2010-02-05T01:07:24Z")
> [@A\_Man\_A\_Plan\_A\_Canal](#): > > My childhood-and-then-into-college sweetheart was a mirror twin whose sister was well documented _situs inversus_. Externally, the two were quite interestingly mirrored: hair sworls, moles, and other slight asymmetries very easily matchable between them. Handedness was mirrored also. I knew a pair of mirror twins in college. They were bar friends of mine (even though I thought it was only one person at first) and didn’t really hang out with one another but they went to the same places at different times. It freaked me out when I found out it was two different people and that explained a lot of things I noticed. One was gay and one was not as well. I don’t know if the two things were related but it was pretty strange. ---
**Author:** ![RadicalPi](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/radicalpi/32/9806_2.png) [@RadicalPi](https://boards.straightdope.com/u/RadicalPi)\ **Post date:** [February 5, 2010, 1:11am UTC](https://boards.straightdope.com/t/is-it-possible-to-be-born-backwards-lateral-symmetry-wise/527674/22 "2010-02-05T01:11:02Z")
> [@A\_Man\_A\_Plan\_A\_Canal](#): > > My childhood-and-then-into-college sweetheart was a mirror twin whose sister was well documented _situs inversus_. Externally, the two were quite interestingly mirrored: hair sworls, moles, and other slight asymmetries very easily matchable between them. Handedness was mirrored also. Wow. You answered my question before I even asked it. Thanks. ---
**Author:** ![Rysdad](https://avatars.discourse-cdn.com/v4/letter/r/7cd45c/32.png) [@Rysdad](https://boards.straightdope.com/u/Rysdad)\ **Post date:** [February 5, 2010, 2:16am UTC](https://boards.straightdope.com/t/is-it-possible-to-be-born-backwards-lateral-symmetry-wise/527674/23 "2010-02-05T02:16:02Z")
Maybe situs inversus is a cause for deferment from the military. I work at a Veterans Hospital, and I’ve taken thousands of chest x-rays, but I’ve never seen one case of it there. The only cases I have seen were during my training at another hospital. They were neonate cases, and, sadly, they didn’t live for long. ---
**Author:** ![Kimstu](https://avatars.discourse-cdn.com/v4/letter/k/ecd19e/32.png) [@Kimstu](https://boards.straightdope.com/u/Kimstu)\ **Post date:** [February 5, 2010, 2:51am UTC](https://boards.straightdope.com/t/is-it-possible-to-be-born-backwards-lateral-symmetry-wise/527674/24 "2010-02-05T02:51:27Z")
I know a pair of identical twins who are mirrored as far as handedness and other externally visible marks go, but I don’t think either of them is situs inversus. (Hmmm, is that possible? Would one of them have to be situs inversus on the inside if they’re mirror-image on the outside? That doesn’t seem right but I can’t spot what’s wrong with it.) ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [February 5, 2010, 9:57am UTC](https://boards.straightdope.com/t/is-it-possible-to-be-born-backwards-lateral-symmetry-wise/527674/25 "2010-02-05T09:57:48Z")
Sinus inversus turns out to be a result of defective cilia, oddly enough. Early in development, cilia set up currents that help determine left-right symmetry. ---
**Author:** ![Quercus](https://avatars.discourse-cdn.com/v4/letter/q/7ab992/32.png) [@Quercus](https://boards.straightdope.com/u/Quercus)\ **Post date:** [February 5, 2010, 1:53pm UTC](https://boards.straightdope.com/t/is-it-possible-to-be-born-backwards-lateral-symmetry-wise/527674/26 "2010-02-05T13:53:47Z")
> [@Bogeyman](#): > > See this [image](http://upload.wikimedia.org/wikipedia/commons/6/6b/Surface_anatomy_of_the_heart.png) on wikipedia. So, aside from the disturbingly hairless chest of that young man, is that accurate at all with the rib cage? I’m not an anatomist, but the rib cage seems way too narrow at the top. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [February 5, 2010, 2:05pm UTC](https://boards.straightdope.com/t/is-it-possible-to-be-born-backwards-lateral-symmetry-wise/527674/27 "2010-02-05T14:05:37Z")
> [@Rysdad](#): > > Maybe situs inversus is a cause for deferment from the military. It was in my Dad’s day - 1940’s, but I suspect it’s the ancillary problems it causes (he has chronic lung problems). ---
**Author:** ![Vorpal\_Blade](https://avatars.discourse-cdn.com/v4/letter/v/9de0a6/32.png) [@Vorpal\_Blade](https://boards.straightdope.com/u/Vorpal_Blade)\ **Post date:** [February 5, 2010, 2:06pm UTC](https://boards.straightdope.com/t/is-it-possible-to-be-born-backwards-lateral-symmetry-wise/527674/28 "2010-02-05T14:06:13Z")
> [@cmyk](#): > > Americans with this condition are also prone to drive on the left side of the road. (wink) And are left-handed. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [February 5, 2010, 3:27pm UTC](https://boards.straightdope.com/t/is-it-possible-to-be-born-backwards-lateral-symmetry-wise/527674/29 "2010-02-05T15:27:12Z")
> [@panache45](#): > > I had an uncle (through marriage) who had \*situs inversus. \*Nobody knew about it until he was shot in the left side of his body, and the surgeon discovered the condition. There are family members who still believe that the bullet caused his heart to jump from the left to the right side. :rolleyes: Perfectly reasonable! - the bullet (or maybe the surgeon)just collapsed the wave function - until that point, his organs were in a superposition of states left and right. ---
**Author:** ![The\_Weird\_One](https://avatars.discourse-cdn.com/v4/letter/t/7bcc69/32.png) [@The\_Weird\_One](https://boards.straightdope.com/u/The_Weird_One)\ **Post date:** [February 5, 2010, 4:54pm UTC](https://boards.straightdope.com/t/is-it-possible-to-be-born-backwards-lateral-symmetry-wise/527674/30 "2010-02-05T16:54:52Z")
> [@Smeghead](#): > > Sinus inversus turns out to be a result of defective cilia, oddly enough. Early in development, cilia set up currents that help determine left-right symmetry. Really?! How fascinating! That helps explain how the condition could be caused by a minor genetic glitch that doesn’t affect anything else. ---
**Author:** ![KarlGauss](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/karlgauss/32/3713_2.png) [@KarlGauss](https://boards.straightdope.com/u/KarlGauss)\ **Post date:** [February 5, 2010, 5:12pm UTC](https://boards.straightdope.com/t/is-it-possible-to-be-born-backwards-lateral-symmetry-wise/527674/31 "2010-02-05T17:12:29Z")
> [@The\_Weird\_One](#): > > Really?! How fascinating! That helps explain how the condition could be caused by a minor genetic glitch that doesn’t affect anything else. Well, if the cilia don’t function properly, then secretions such as mucous may not be cleared (as they usually are, in part, by ciliary action). The result can be chronic and rather severe infections of the lungs and sinuses. **ETA:** : As noted upthread, see [Kartangener Syndrome](http://en.wikipedia.org/wiki/Kartagener_syndrome) ---
**Author:** ![Attack\_from\_the\_3rd\_dimension](https://avatars.discourse-cdn.com/v4/letter/a/b38774/32.png) [@Attack\_from\_the\_3rd\_dimension](https://boards.straightdope.com/u/Attack_from_the_3rd_dimension)\ **Post date:** [February 5, 2010, 5:55pm UTC](https://boards.straightdope.com/t/is-it-possible-to-be-born-backwards-lateral-symmetry-wise/527674/32 "2010-02-05T17:55:45Z")
> [@Smeghead](#): > > Sinus inversus turns out to be a result of defective cilia, oddly enough. Early in development, cilia set up currents that help determine left-right symmetry. I’d love to see a citation about how this works. If you could point me in that direction I would very much appreciate it. ---
**Author:** ![KarlGauss](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/karlgauss/32/3713_2.png) [@KarlGauss](https://boards.straightdope.com/u/KarlGauss)\ **Post date:** [February 5, 2010, 6:15pm UTC](https://boards.straightdope.com/t/is-it-possible-to-be-born-backwards-lateral-symmetry-wise/527674/33 "2010-02-05T18:15:53Z")
> [@Attack\_from\_the\_3rd\_dimension](#): > > I’d love to see a citation about how this works. If you could point me in that direction I would very much appreciate it. Look up, right above. ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [February 5, 2010, 7:45pm UTC](https://boards.straightdope.com/t/is-it-possible-to-be-born-backwards-lateral-symmetry-wise/527674/34 "2010-02-05T19:45:07Z")
Karl’s link, as well as the linked page on situs inversus, have some information on it, for which I thank him. I don’t know a lot about it myself - I’m loosely familiar with it mainly because one of the labs in my building studies cilia, and they always begin their presentations with a list of diseases caused by cilia defects, so it’s been drilled into me. IIRC, basically what happens is that in an early embryo, there are cilia that beat and set up a current going in one direction. Cells secrete growth hormones, and they get caught up in the current and are swept in one direction, where they land on other cells. This sets up a situation where cells on one side of the embryo are getting these hormones and cells on the other side are not. This ultimately leads to left-right asymmetry. If the cilia aren’t working properly, this process doesn’t work reliably, and there’s a 50/50 chance of screwing up right and left. [Previous page](https://boards.straightdope.com/t/is-it-possible-to-be-born-backwards-lateral-symmetry-wise/527674.md?page=1)