Researchers have uncovered new insights into the genetic underpinnings of human facial likeness and physical similarity in an intriguing nature versus nurture study on real-life look-alike pairs.
Key Findings:
- 50% of look-alike pairs studied shared high genetic similarity, despite being unrelated
- Over 19,000 SNPs were identified that were shared across genetically similar look-alike pairs
- These SNPs were enriched in genes related to facial morphology, body structure, and cell adhesion
- Look-alikes also showed stronger similarities in DNA methylation age, weight, and lifestyle habits
- Genetic factors appear to be the main driver of human likeness, over epigenetic or microbiome factors
The age-old question of nature versus nurture continues to intrigue scientists and philosophers alike.
To what extent is human appearance and behavior shaped by genetics versus environmental factors?
An unusual study on real-life human doubles is providing new clues into this mystery.
Researchers recruited 32 pairs of complete strangers that bore an uncanny physical resemblance to each other.
These look-alike pairs were identified by Canadian photographer François Brunelle through his online project that has documented doppelgängers from across the globe.
The study subjects, who ranged from ages 21 to 78, provided saliva samples that enabled a comprehensive multi-omics analysis of their genomes, epigenomes, and microbiomes.
Lifestyle questionnaires were also completed to examine similarities beyond physical appearance.
Objectively Quantifying Facial Similarity
To objectively quantify facial similarity, photographs of the look-alike pairs were run through three different facial recognition algorithms.
Impressively, 16 of the 32 pairs (50%) were consistently rated as matches by all three programs.
For context, the facial match scores for these 16 look-alike pairs were on par with comparisons of identical twins.
This demonstrates an extremely high degree of visual likeness to the naked eye and computer vision.
Genomic Insights into Human Likeness
Next, the research team dove into the genomic data to understand if this extraordinary physical similarity was underpinned by genetic similarity.
DNA samples from the cohort were run through a microarray that surveyed over 4 million sites across the genome.
Incredibly, 9 of the 16 visually matched look-alike pairs (56%) also clustered together based on genetic similarity.
The researchers coined these pairs “ultra look-alikes”.
Across these 9 genetically matched pairs, 19,277 SNPs were consistently shared. SNPs, or single nucleotide polymorphisms, are genetic variations that make each person unique.
This finding reveals that a subset of SNPs is linked to determining facial appearance and physical resemblance.
The genes annotated to these SNPs showed enrichment for several ontologies related to anatomical development, cell adhesion, and bone and skin properties.
Enrichment was also found in GWAS hits for facial morphology, body measurements, and craniofacial dysmorphisms.
Together, this demonstrates that human likeness has a strong genetic underpinning, with certain SNPs exerting a major influence on the eventual construction of the face and body.
Beyond Genetics: Methylation, Microbiome, and Lifestyle
While genetics emerged as the main driver of look-alike phenotypes, the study also examined epigenetic, microbial, and lifestyle factors.
At the epigenome level, DNA methylation pattern clustering only matched 1 of the 16 visually similar pairs.
However, the researchers noticed that epigenetic age differences were smaller between genetically matched look-alike pairs versus non-matched pairs.
This hints that while overall methylation patterns are distinct, epigenetic aging could be a relevant process in modulating facial morphology over a lifetime between genetically similar individuals.
In terms of the oral microbiome profiles, only 1 look-alike pair matched compositionally.
However, weight differences were smaller amongst genetically similar pairs.
This raises the possibility of microbial links to fat distribution and facial adiposity.
Lastly, when comparing lifestyle questionnaires, the researchers found that look-alike pairs showed greater similarities in physical traits like height and weight as well as behaviors like smoking and education level.
Overall, their results fit with the theory that human likeness stems from genetic similarities, while environmental factors contribute to diversifying otherwise similar individuals.
Similar Facial Physiognomy: Implications
This intriguing study provides a rare glimpse into the molecular basis of human facial resemblance.
Beyond illuminating basic biology, these findings could have meaningful impacts across disciplines like biomedicine, forensics, and social media.
For medicine, linking facial genetics to physical traits could bolster diagnosis of genetic disorders and biometric predictions from DNA.
On the forensics side, these results reinforce the need to consider genetic testing alongside eyewitness accounts and photographic evidence in criminal investigations whenever look-alikes are involved.
Social media-wise, an enhanced understanding of the genetics of facial shapes could lead to smarter algorithms for tagging photos or detecting profile impersonations.
Of course, ethically ensuring these applications remain voluntary and consensual will be paramount as the science continues maturing.
Looking to the future, expanded analyses on larger and more diverse genetic samples, combined with 3D facial imaging, could allow even finer mapping between genotypes and facial structures.
The researchers also point to molecular profiling of skin and adipose tissue as ways to further dissect the “nature versus nurture” balance.
While debates on this topic will doubtlessly continue, this unique study marks an important step toward unlocking the secrets behind human individuality, diversity, and resemblance encoded within our genomes.
With additional data, we inch closer to understanding the intricate interplay between our inherited blueprints and lived environments that sculpt each of our unique, yet occasionally familiar, faces.
References
- Study: Look-alike humans identified by facial recognition algorithms show genetic similarities
- Authors: Ricky S Joshi
