Nancy, I'm a father of fraternal twins and have opportunity to discuss this with doctors and geneticists. Here is how I understand it.
Identical twins are purely random. Fraternal twins, the result of more than one egg, can seem to have a higher incidence in some families, but other factors effecting this have more influence than geographic origin. The incidence of twining is higher for women between 30 and 40 years of age, of greater than average height and weight, and have had multiple pregnancies. If you have a population where women tend to have many children and later in life, there will be more twins. Men have nothing to do with this . It is not a trait passed from fathers to daughters. Women set the target, men just hit it. There is a study that suggests that the of West Africa population especially the Yoruba has a higher rate of twins. Eric Edgar On Wed, Jun 16, 2010 at 3:05 PM, Nancy Couto <nvco...@hotmail.com> wrote: > I could be wrong, but I think that the genetic factor is applicable only to > the mother of fraternal twins. That is, the mother has to release two eggs > at approximately the same time. No matter how high the father's sperm count > is, there have to be two eggs. > > For identical twins, of course, there is a single egg that divides. > > I don't know anything about medicine, but when I was in high school (many, > many years ago) I wrote a term paper on multiple births for my biology > class. I had twin cousins, and I was fascinated with the subject. > > If anyone in the group has a medical background, please feel free to > confirm or correct. > > Nancy > > > ------------------------------ > From: carab...@aol.com > Date: Wed, 16 Jun 2010 13:48:58 -0400 > > Subject: Re: [AZORES-Genealogy] Twins > To: azores@googlegroups.com > > > My gg grandfather, Thomaz Jose da Silveira was a twin. He & his brother, > Domingo were baptized in the Calheta do Nesquim parish on Pico, on 20 July > 1866. He had a grandson that fathered twins, a boy & a girl, in 1938, in > Washington, D.C. > Sherry > > > > -- > To unsubscribe from this group, send email to > azores+unsubscr...@googlegroups.com<azores%2bunsubscr...@googlegroups.com>. > Follow the confirmation directions when they arrive. > For more options, such as changing to List, Digest, Abridged, or No Mail > (vacation) mode, log into your Google account and visit this group at > http://groups.google.com/group/Azores. Click in the blue area on the right > that says "Join this group" and it will take you to "Edit my membership." > ------------------------------ > Hotmail has tools for the New Busy. Search, chat and e-mail from your > inbox. Learn > more.<http://www.windowslive.com/campaign/thenewbusy?ocid=PID28326::T:WLMTAGL:ON:WL:en-US:WM_HMP:042010_1> > > -- > To unsubscribe from this group, send email to > azores+unsubscr...@googlegroups.com<azores%2bunsubscr...@googlegroups.com>. > Follow the confirmation directions when they arrive. > For more options, such as changing to List, Digest, Abridged, or No Mail > (vacation) mode, log into your Google account and visit this group at > http://groups.google.com/group/Azores. Click in the blue area on the right > that says "Join this group" and it will take you to "Edit my membership." > -- To unsubscribe from this group, send email to azores+unsubscr...@googlegroups.com. Follow the confirmation directions when they arrive. For more options, such as changing to List, Digest, Abridged, or No Mail (vacation) mode, log into your Google account and visit this group at http://groups.google.com/group/Azores. Click in the blue area on the right that says "Join this group" and it will take you to "Edit my membership."
