Identical twins and heredity

The question came up again on an online forum. And, once again, folks hopped into the discussion with both feet, readily giving incomplete and misleading answers with confidence.
The question?
Can the tendency to have identical twins be inherited?
The most common answer and the prevailing theory is "no."
Most OBs will tell their patients that identical twins are fluke, an accident of nature, and that their chances of having another set are no greater than any other woman's chance of having identicals in the first place.
But how does that explain my neighbor's daughter and her family? She has three sets of identical twin boys who come trick-or-treating to our house every year.
And what about the woman whose daughter took dance lessons with my daughter? She is an identical twin and she has identical twin boys of her own.
Then there is the woman I met at a local bakery. She looked longingly at my boys (who were screaming at my attempt to get some coffee, unwilling to be pacified by cookies) and told me that her two daughters each have a set of identical twin girls.
It just doesn't make sense.
The reality is that scientists have no idea why some women have identical twins and some don't. Evidence does exist that many sets are flukes. For instance, there is no history in my family or in my husband's of identical twins as far as we know.
My side boasts a set of twins and a set of triplets way back in the olden days, but they were fraternal. My mother-in-law remembers a set of triplets birthed by a distant relative, but they also were fraternal.
So our boys probably were an accident of nature, an awesome accident.
But in other families, the frequency is too great for simple coincidence.
The journalist in me demanded that I do some research.
This is what I found:
A 2007 study, led by Dr. Dianna Payne, a visiting research fellow at the Mio Fertility Clinic in Japan, shows that identical twins form just after conception when an embryo collapses and splits in two. She discovered this by photographing growing embryos every two minutes in a lab using special computer software.
Her evidence negates previously held theories that the egg splits after it leaves its shell immediately before implantation and that, therefore, identicals either shared a placenta or had individual placentas that grew close together. The predominance of the previous theory explains why my OB insisted that our boys were fraternal until they were DNA tested.
Our boys each had their own placentas, which grew on polar opposite side of my uterus.
They were born in January of 2007, just before Dr. Payne and her colleagues went public with their research.
Dr, Payne's discovery has opened new paths for research into the potential genetic impact on identical twins. A study is currently underway that proposes that a male enzyme is involved. Scientist already know that the enzyme causes the embryo to collapse, but they are unsure who secretes it or why.
The study, as far as I know, is not yet public.
But I found this post-- written by a graduate bioengineering student who is helping to conduct the study at an unnamed university--on a Yahoo forum (http://www.twinslist.org/idfaq.htm). She says that the study also suggests some women carry a gene that prevents the enzyme from splitting the egg, and that men who produce the enzyme do not produce it every time:

"Thus far, the research shows that the enzyme is directly responsible for causing the splitting of the chromosomes, which results in the division of the cytoplasm which results in two eggs! There are a few (about 1%) that have alluded us so far and have shows no sign of the enzyme despite the fact that twins resulted. Thus, we have concluded that identical twinning can also be a random event. But in about 99% of the people tested, the enzyme is apparently the culprit. So, 99% is a darn good yield! So, according to our research, it is not a small percentage but almost the entire percentage."

This part of the post explains why we know so little:

"And yes, this study has been repeated already, but very, very little money is put into this research, so most of it is done on our own time. The reason for this is there is little to no medical advances that can come out of the research, just info and most of the money on medical and genetic research is for improving the outcome of diseases, etc. So, that is why it may be a while before this research is completed. We have to get about 5% of the public who have twins to complete our research (not all will go through tests, some will just answer questionnaires) before we can say that this represents the entire population, so you can see that this will take a while!"

So that's it.
The answer is that there is no definitive answer because the people in medical community, or rather the folks who fund their research, are just not not all that interested.
For now, identical twins remain a mystery.

Summer Fun

Here are a few photos of the boys playing in their pool in the back yard. They are now two years and four months old.

Jon is holding Elmo. Matt is "swimming."

Jon (with back facing camera) gives his twin a kiss.

Matt "swimming."

I must admit that in this photo, I have no idea which twin is jumping off the picnic table.

A closer look

It's strange and, maybe, it's just a phase, but I find that I rarely think of Matthew and Jonathan as identical twins these days.
All I can figure is that I am so focused on the intimate, complex achievements that come with this age, that I am unable to step back and see them from any kind of distance anymore. Their recent developments have given me the opportunity to see the minutia and, in the minutia, I see two little people who are so very different from each other.
For instance, language has given them the tools to verbally express their individuality, like Jonathan and his obsession with Swiper the Fox, an obsession that Matthew does not share:
"Swiper?"
"Fox?"
"Sneaky?"
"Naughty?"
"Oh man!"
(Repeat ten times and insist that mom repeat each word as affirmation that she is listening.)
Or Matthew with his bathing preferences, preferences that Jonathan clearly does not share:
"No toys!" Matthew shrieks as a small zebra, a cup and a teething ring come flying out of the bathtub. Jonathan stands, reaches in vain for the discarded playthings and then throws his hands up and cries.
"Toys done," Matthew says triumphantly. "No toys!"
Improved mobility and agility has given them the skills to individually test their physical limits while also applying the techniques of observation and manipulation.
For instance, Matthew has learned to appear fully absorbed in play in their fenced-in area out back, leaving me with a sense of security as I try to sneak inside for a moment to unload the dishwasher. As soon as my back is turned, he is over the fence and around the front of the house. Jonathan remains fenced in, too awed to throw a leg over and follow.
Jonathan, meanwhile, is focused on his jumping skills. He arranges bean bag chairs a few feet away from the sofa and then, calculating the distance just perfectly, he leaps from the sofa into the bean bag chairs face-first.
Greater reasoning ability, empathy and perspective has given them both the skills to manipulate their environment and the people in it to their liking.
A few examples:
Matthew will turn my head in his direction with his tiny hands, cock his own head in the cutest little way, scrunch his eyes just right and say, "Cars? Watch Cars?" He knows he makes my heart melt. He knows I can't resist. In goes the Cars DVD.
Jonathan keeps one eye on his brother and waits for that moment when Matthew wants to cuddle with me. Then he runs over, pushes his twin brother aside, climbs into my arms and declares, "Mine! Mine!" As soon as Matthew loses interest in the battle for attention, Jonathan slips off my lap and resumes play.
Matthew climbs onto the sofa, lays his head on a pillow and covers himself with a blanket, just like his older brother does each morning when he first wakes up. And then, in his desire to complete the charade, he says, "Ovaltine? Ovaltine?" requesting his idol's favorite drink and hoping it gets his attention.
Sometimes, when I am crouched down, picking raisins off the floor, scrubbing milk out of the carpet or scooping up bits of crushed crackers, I'll feel two perfect hands tickle my neck and Jonathan will be standing right in front of me. He'll say "love!" and then kiss me right on the lips. Just as he predicts, I stop what I'm doing and cradle this amazing human being.
It was a lot easier when the twins were more like a unit, when I could step back and say this is who "they" are, this is what "they" do, how "they" behave. Still, I wouldn't ever want to be positioned so far away again.
This new phase is exhausting, but it's also exhilarating.
I am finally getting the chance to know them, to know them as individuals.
As Matthew and Jonathan, brothers who just happen to both be two.

Anger management

When Matthew and Jonathan are angry with each other, they do what many siblings their age do: they hit each other.
So what do they do when they are angry with me?
They hit each other.
I haven't quite figured this one out.
I've talked to other twin moms, assuming this must be a common issue.
It's not.
No one had answers for me.
All I can figure is that jealousy plays a role; Matthew and Jonathan are so accustomed to each other that, somehow, whenever they are angry with me, they figure it must be the other twin's fault.
This phase has convinced us of one thing: it is time to work harder at separating them now and then. They need to learn to handle their emotions as individuals, not as a team.
Since it seems that we're at the grocery store just about every day, that's where we'll start.
A trip for Jonathan today.
A trip for Matthew tomorrow.
And maybe, just maybe it will work.
Maybe, next time I evoke their fury, they'll channel their emotions appropriately.
They'll hit me instead of each other.
Wait a minute ...
What the heck are we doing?