[Yair Doza (OP)]

Hello

Just having identical twin girls I was thinking - each sex cell that produces identical twins double its chance of passing on its genes. There might be a positive selective trend to have genes  that produce identical twins. Yet twins are rare!

Perhaps the reason is that a lot of twin pregnancies are not successful, so the positive selection to have twins is countered be the negative selection of low survival.

In that case, with modern medicine saving most twin pregnancies (our was saved by intensive medical care) are we creating future generations where there will be more and more identical twins?

Are there families with more identical twins in them that in the general population? Did anyone identified a gene causing formation of identical twins?

What do you think? Thanks for reading Yair

[SeanB]

Yes there are families where twins are more common. As to this being a good selection or not is really going to depend more on environment than anything else, as twins need better nourishment from the mother, and demand twice the attention and care for the infants. It may be difficult to see any advantages or not, as twins have been born since recorded history began.

[RD]

If the pros outweighed the cons, multiple births would be the norm.


Having dizygotic twins can be hereditary, (inherited hyperovulation).

However I don't think having monozygotic ("identical") twins is inherited ...

Spontaneous division of the zygote into two embryos is not considered to be a hereditary trait,
 but rather a spontaneous or random event.

http://en.wikipedia.org/wiki/Dizygotic#Monozygotic_twins

i.e. a mother who is identical twin is not at a greater risk of having identical twins than a mother who is a singleton.