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Study Finds DNA Similarities Among Look-alikes

by Eike Blohm, MD

A recently published study shows that “doppelgängers” — unrelated strangers who look eerily similar — don’t just share looks; they have similar DNA.

The advent of social media and ubiquitous cellphone cameras has resulted in some people discovering their virtual twin. Two unrelated individuals who look so alike that they could be mistaken for identical twins are termed “doppelgängers,” which translates from German as “walking doubles.” Doppelgängers can be geographically or contemporarily distant. A popular internet meme shows the actor Keanu Reeves next to centuries-old oil portraits and sepia photographs of individuals who look exactly like him, concluding that Reeves must be an immortal vampire.

Online fads aside, a team of researchers at the Josep Carreras Leukaemia Research Institute in Barcelona, Spain, sought to analyze the degree of genetic similarities among these identical strangers. Thirty-two doppelgänger pairs from across the globe were recruited from the work of Canadian artist François Brunelle and underwent facial recognition analysis, kinship analysis, and genetic testing.

Half of the pairs had high correlation scores on three different facial recognition software programs. Of those, nine pairs also shared multiple random DNA mutations despite being unrelated. These single-nucleotide polymorphisms (“SNPs”) are one-letter variations in our genetic code that have no detrimental effect on the information stored in the DNA. A linguistic analogy is that Americans spell the color of this paper as “gray” while the British use “grey.” Although one letter differs, the information conveyed is unchanged.

In forensic science, the analysis of SNPs is used to establish whether two DNA samples match naturally. DNA from the same individual should match close to 100% of SNPs (mutations acquired as we age precludes perfect matching). In the doppelgängers study, only 19,277 of the 4.3 million SNPs matched. While facial recognition fails to distinguish these look-alikes, and while doppelgänger pairs have more DNA similarities than would be expected by random chance, the genetic overlap is limited enough that modern microarrays for SNP analysis can differentiate the two individuals.


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