Dutch-led research team discover the cause of identical twins

An international group of researchers headed by scientists from the Vrije University Amsterdam (VU) has, for the first time ever, discovered a biological explanation of what causes identical twins.

The group, led by biological psychologist Jenny van Dongen and professor Dorret Boomsma of the VU, found that it is not the DNA of identical twins that they should be looking at. Rather, they discovered that there’s a certain substance that attaches itself to the DNA, The NOS reports.

Differently packaged DNA

The researchers discovered that the DNA of identical twins is “packaged” differently than that of other people. In a program on NPO Radio 1, Boomsma said that everyone has what is known as methyl groups attached to their DNA.

However, “It turns out that in more than 800 places in the DNA, the methylation is different in identical twins than in the rest of the population.” Boomsma added that this process probably starts very early after conception.

Quick biology lesson: identical twins occur when a single fertilized egg splits in two. Fraternal twins (A.K.A. non-identical ones) develop from two fertilized eggs. 👩‍👧‍👦

A mystery solved

According to Boomsma, “This is a very big discovery because the origin and birth of identical twins has always been a complete mystery.” 😱 This revelation is also important for research into birth defects.

More than 6,000 twins

In doing this research, the scientists looked at the DNA of more than 6,000 twins — using twin registries from the Netherlands, Great Britain, Finland, and Australia.

What are your thoughts on this groundbreaking discovery of the origin of identical twins? Tell us in the comments below!

Feature Image: Hannamariah/Depositphotos

Jen Lorimer 🇿🇼
Jen Lorimer 🇿🇼
An avid tea drinker, Jen was born and raised in Zimbabwe. She moved to Utrecht in 2017 to pursue her history degree. She loves people-watching, canoeing the Utrecht canals, and observing how the Dutch come alive in summer. Having been traumatised by a Dutch circle party, Jen wants to help equip other internationals with tips and tricks to survive and thrive in this wonderful flat country.


  1. It’s a stupid report bc everyone has known since like ivf and test tube babies how identical twins occur and how they have the same dna and fraturnal occur but my only question has only been can a set of fraturnal twins be only identical.on the mother’s side and have two different father’s causing them to look so similar but not? Or was it the close implantation of the twins where they were conceived eight days a part bc their placenta was fused together and they had two different embryotic sacs and we’re C-section and I had last been with one man 2-2-1993 and then the other from then on and their due date was Nov 9,1993 but they were taken by emergency C-section on 10-4-1993 they say that being identical only on the mother’s side only happens in animals


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