Friday, April 01, 2011

How identical twins aren' t identical

I interrupt my April study of the medical signs of a twin conception to bring you this, which arrived in my inbox today via the Vanishing Twin forum.
A scientist in Montreal has finally proven what a lot of people have been finding -  that "identical" twins aren't identical.  Read it here, you will be amazed. 

But after sequencing the DNA of twins and their parents, and looking at one million differences between their genes, Singh concluded that twins are not actually identical.  "Our results have really forced everyone to rethink the idea that identical twins are actually identical," he said.

In writing the new book "Womb twin survivors"  I describe the sole survivors of monozygotic (MZ) , dizygotic (DZ) and multiple conceptions. I had to struggle with  difficult terns like MONOZYGOTIC  to  describe identical twins, because they arise out of one zygote and look very similar but I discovered early on they are do NOT have identical genes. This new study seems to prove that very nicely.
Epigentics rule! What happens before birth influences you for the whole of your life, be you MZ or not  - as if womb twin survivors need convincing of that, but science is after all a very slow process of proving the obvious......
So if you are a monozygotic (MZ) wombtwin survivor,  rest assured that your other half was not exactly like you - another version of yourself.   Your MZ twin was so different from you that he or she didn't survive to birth as you did. You are a unique individual, not a clone.
The Montreal study also casts doubt on every piece of twin research ever conducted, which relies on comparing MZ twins with DZ twins, on the assumption that MZ twins share a complete set of genes - wrong.

My new book did not come out a moment too soon!
Mixed reviews so far, but then it's 375 pages, 70 illustrations, 300 references plus appendices.  It's so packed with information it will take a lot of reading before we get a true result, but I thought it would be fun to record the first responses: 
  • "Beautiful and fascinating."
  • "The pages will make a good starter for my wood burner......." 
  • "Can't wait to receive my copy...."


  1. I've heard of this before. From the moment of conception, each twin goes off on their own. As each cell of each twin replicates, there will be, over time, slight differences made in the copying process.

    Depending on where the differences lie, I guess this will invalidate a lot research where one identical twin has been used as a control subject?

  2. I wonder what twin researchers have made of this. As you say it is well known, but they don't seem to have factored it in. They doesnt sem to be much use in comparing DZ and MZ twins and then applying what they have learned to the general population,for not only are an unknown number of DZ twins reduced triplet sets where one survivor was once an MZ twin but their co-twin died, but also an unknown number of MZ twins are reduced triplet set and had a third embryo present for a while. Then to add to the mix up, in the general population there are 10% or more who are womb twin survivors. This is why I have long since ceased to look for a reliable control group in my research!!