Physical similarities between strangers

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Surely throughout your life you have come across a person who reminds you of a friend, family member or acquaintance. If you have found yourself in this situation and you are wondering how this can be possible, you are in the right place. In this article, we talk about strange twins.

Are there people who, without being twins, seem so?

As it could not be otherwise, genetics, once again, has the answer to this question.

Thanks to the identification of physically similar people (32 pairs), it has been possible to analyze at the genetic level what was happening in these cases.

The identification of these couples (physically similar people) was made from the photographic work of François Brunelle. A Canadian artist who has been obtaining images around the world since 1999 of physically very similar people with no family relationship.

However, in order to confirm that there is no degree of kinship between these couples, the study that analyzed this phenomenon carried out an analysis of IBD (from its acronym in Englishés, "identity by descent") in which only a couple shared genetic variants in proportions compatible with third-degree relatives. For the rest of the couples, although it seems surprising, the existence of a degree of kinship was ruled out (Figure 1).

Pairs of people with genetically unrelated physical resemblances - Unrelated Twins
Figure 1. Pairs of people with genetically unrelated physical resemblances

Individuals characterized by their great resemblance are colloquially called similar humans, unknown twins, strange twins or doubles.

Genetics shared by strange twins

In addition to the set of strange twins (LAL in Figure 2), monozygotic or identical twins (MZ-twins in Figure 2) and people without physical resemblance and without family relationship (Non-LAL in Figure 2) were analyzed in order to make a more exhaustive comparison. These three groups of people had their DNA analyzed in such a way that it was possible to develop a similarity score. This score is statistically significant between the three groups, confirming that indeed, at the genetic level, there is a similarity between the unknown twins (much greater than the "Non-LAL" and less than that of the monozygotic twins – identical twins).

Similarity between monozygotic or identical twins (MZ-twins), unknown twins (LAL) and unrelated persons without physical similarity (Non-LAL).
Figure 2. Similarity between monozygotic or identical twins (MZ-twins), strange twins (LAL) and unrelated and physically unsimilar people (Non-LAL).

If we dig a little deeper, of all the genetic variants that were analyzed, it was seen that 113 genetic variants (SNPs) corresponded to traits related to facial features or physical traits.

Facial similarity associated with shared genetic variants

The study we rely on shows that stranger twins share genetic variants in their DNA. It is not about kinship, but chance. Sometimes, identical areas or DNA sequences are originated in several people.

Due to the difficulty in obtaining this type of data, the sample size is small, which restricts the ability to perform large-scale statistical analyses. It is also important to note that the study was limited to the analysis of SNPs, preventing the analysis of other genetic components such as structural variations.

However, a collection of photos of genetically unrelated look-alikes, along with DNA analysis, has revealed that a strong facial similarity is associated with shared genetic variants.

In ADNTRO we cannot find you an stranger twin, but we can evaluate the degree of kinship you have with your samples. What are you waiting for to find it out?

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