Twin DNA and Variations in Genetic Ancestry

The Agro twins from the CBC News ancestry DNA test results comparison video discover they have different nations under their continental analyses in their ancestry origins. One says Poland is a possible match while the other says Poland is “not detected.” One twin had “French and German” in her results at 2.6% while the other didn’t have French or German whatsoever. One is 28% “Broadly European,” the other twin 12.7%. These seem to be differences that to many, make no sense when it comes to identical twins.

In fact, one twin went to visit a team at Yale University, a team that studies DNA. She was told that, with both she and her sister being identical twins, their DNA is the same and thus, they should have the same exact ancestral origin analysis. “It’s scarily the same,” one person on the team said. The DNA companies state that the Agro twins have 99% genotype consistency — that is, genotype, which means ”

“Why would Carr be more Eastern European than I am if our DNA is the same?” The other twin sister asked. “She’s not, there’s nothing to say. You and your twin sister have the same genetic ancestry,” the same team member said. The team said that the differences between the two twins (one being 28% Eastern European, the other 24.7%) is based on the analysis of 23andme. In other words, “the science says that both of the twins have the same genetic ancestry.”

But is that true? Is it the case that both twins have the same genetic ancestry, that the genes reveal the same ancestry behind their DNA markers? Well, that claim seems to be too easy an answer based on next-generation genome sequencing. According to a Wired article from 2014, a German company called Eurofins Scientific has created a test that can detect genetic mutations in identical twins. The new testing method examines the 3 billion DNA markers of identical twins and finds the variations between them: “Because mutations randomly occur during development, even genetically ‘identical’ twins will vary at a handful of locations,” according to Eurofins Scientific forensic scientist Burkhard Rolf. These genetic variations were used to arrest one of two twins accused of crimes stretching back some years. His twin brother also had his DNA in the justice system. With two twins that both had criminal activity on their records, convicting either of their crimes for years had been next to impossible.

What explains these genetic variations or small changes in genetic structure? According to scientists, adulthood, when twins separate and move to different places, eat different foods, have different work and life routines, and so on. Sure, twins are born with the same genes as babies, but those genes are not just impacted by nurture (being raised the same) but also by nature. Certain environmental factors affect genes. Those environmental factors are different for twins who move to different cities, states, or even countries. So with that said, twins can have nearly identical DNA yet have some slight variations in genetic makeup.

If genetic variations exist, it’s possible those variations explain why one identical twin has a greater percentage of ancestry from Poland while another does not (or doesn’t register any at all). I’m not implying here that these identical twins don’t have the same ancestry. If they have the same mother and father, they do. However, what I am saying is that, contrary to the team mentioned above, I don’t think the genetic variations that come out in DNA testing are due to company algorithms and formulas. Rather, I believe those genetic differences on paper are due to actual genetic variations within adult identical twins. It’s interesting to note that the YouTube video from CBC was published in 2019, nearly 18 months ago, yet a study regarding distinguishing identical twins introduced in 2014 was not included in its assessment.

And, as for why one doesn’t have any Polish ancestry via DNA? She didn’t get the same exact DNA markers as her twin. It doesn’t make her “not Polish,” but rather, someone whose DNA doesn’t reflect her Polish ancestry.

Conclusion

It’s assumed that, if identical twins have the same DNA, they will have the same exact DNA markers and their ancestral results will be the same. But that simply isn’t true. Why is that so? Because these identical twins are still two different people.

I think the problem that ancestry tests highlight is that identical twins are assumed to be identical in every way. And yet, that simply isn’t true. There are identical twins who later in life have different eye colors. Some identical twins end up being taller or shorter than others. Others have different hair color and textures. And, of course, we can’t forget about fingerprints. While identical twins may have near-identical DNA, their fingerprints are different. Fingerprints can tell them apart.

And I think that these ancestry tests show that, as close as twins are, they are still distinguishable. For, if they can’t be distinguished, they’re not two people but rather, the same person. And we wouldn’t want to wipe away their uniqueness, would we?

Of course not.