The human face is a complex trait composed of distinct features
(i.e., eyes, nose, chin, and mouth), whose size, shape, and composition are clearly heritable.
In fact, studies on twins have shown that approximately 75% of the face’s composition
is genetically influenced, but that doesn’t necessarily mean it’s inherited as mutations,
and disruptions also come into play.
Slight variations of genes can essentially affect every aspect of the facial morphology
of a human and so, an endless possible combination can virtually form infinite facial forms with
varied facial structures.
It has been hypothesized that human faces are subject to more variations than the faces
of other species or even other parts of our body.
Nevertheless, from the strong facial resemblances that exist among members of a family, it is
evident that genetics plays a vital role in producing attractive faces.
On the other hand, the fact that facial malformations and syndromes can be heritably passed down
from parent to offspring provides further proof that genetics does indeed play a critical
role in shaping the human face.
It has been identified through a study by Tsagkrasoulis and colleagues which aspects
of our face are most and least heritable.
This study utilized high-resolution, three-dimensional facial models of a cohort of 952 twins.
Their unique algorithm then identified thousands of landmarks across the face and automatically
established point-wise correspondence to measure differences.
These landmarks then enabled the researchers to accurately define facial geometry in fine
detail with curvature measurements thus revealing accurate heritability maps of the human face.
From these results, the researchers found strong heritability in the mental region (chin),
philtrum (upper lip), nasal tip and nasion, inner eye corners and maxilla (upper jaw).
Of these findings, the maxilla is one of the most significant aspects for facial beauty
as it influences forward growth and provides support for a multitude of facial components
where without proper development common cosmetic flaws like scleral show, jaw recession and
paranasal hollowing become more apparent.
Also, using a multivariate analysis, the researchers found heritability in the nasolabial folds
(smile lines) and undereye regions both of which, again, are regions influenced by maxillary
forward growth.
Due to the advancement and application of high-throughput genomic technologies in the
last 2 decades, there has been a dramatic increase in gene discovery for all craniofacial
phenotypes.
Genome-wide association studies (GWAS) conducted since 2005, have presented evidence that common
traits and diseases are affected by common DNA sequence variants.
Several genome-wide association studies (GWAS) have each identified 25 of the loci associated
with a small number of facial traits.There is a ridiculously long list of genes and their
facial influences summarized in this table here from Stephen Et al’s Facial Genetics:
A Brief Overview which we’ve gotten permission to reproduce over at the QOVES website.
The most infamous example of this is the Hapsburg jaw where a series of incestous marriages
down the European family tree over 3 centuries led to the offspring developing a characteristically
bad mandibular prognathism or underbite.
From this image, it’s very clear to see the how a disruption in normal jaw alignment,
especially at the maxilla leads to distinctly droopy, rounded eyes, a heavily plunging nose
and a pointed chin, all of which fall in the mentioned heritable regions from the previous
study.
In reality these facial deformities come about often as a failure in only a small handful
of genes for instance in the case of children with cleft palate.
By comparing the children with this deformity to their unaffected relatives, Millet Et al
2014 found that the affected face had reduced facial convexity (SNAI1), increased chin protrusion
(SNAI1, IRF6, MSX1), increased lower facial height (SNAI1) and thinner, retruded lips
with larger foreheads (ABCA4-ARHGAP29, MAFB).
All of these genes are relevant for normal facial growth in telling the cells to replicate
by how much and for how long and these shared genetic pathways can get mixed up even when
it’s not inherited.
In contrast, there are also features that aren’t influenced by your inherited genes
and instead by the surrounding environment.
There’s an ongoing theory supported by a body of evidence that human noses are adapted
to their environment by race and ethnicity.
We’re actually working on a full video for the topic and if you’re enjoying the content
so far, there’s no reason to not subscribe now to catch that video too.
In short, ethnicities in colder climates have smaller, sharper noses while those in hotter
ones have wider, flatter noses in an effort to maximise airflow when hunting.
Fetal alcohol syndrome also produces characteristic features right from birth and there’s an
endless number of pregnancy medications such as hydantoin that can produce abnormal features.
From Hoyme and colleagues recommendations on fetal alcohol diagnosis, the very next
stage is to assess the patient’s face because it’s that influential on the face.
This process involves taking head circumference measurements which are often bigger than average,
having a smooth philtrum, thin lips and beady eyes.
In a GWAS conducted by Fan Liu et al. facial features were phenotyped according to landmark
data retrieved from 2-D portrait photos and 3-D magnetic resonance images (MRIs) of the
head.
Five independent genetic loci, so a small part of an individual chromosome, were identified
from this study which was related to different facial phenotypes.
This implied the involvement of the candidate genes; PRDM16, PAX3, TP63, C5orf50, and COL17A,
in the determination of the human face.
Three of these candidate genes have been identified in earlier studies in relation to craniofacial
development and disease in vertebrates.
The remaining two genes are probable new factors in the molecular networks that guide facial
development.
These genes likely have little relevance to you, but the recurrence of one gene, PAX3,
in facial abnormalities and unique facial features is crucial in forensic profiling.
To date, it’s understood that PAX3 influences the prominence of the nasal bridge which itself
is a unique facial trait for some.
Take Tibetan model Tsunaina who is regarded for her wide nasal bridge and attractive proportions
in the industry.
Someone with a PAX3 mutation would be limited to only a handful of people in the world with
a feature as distinct as hers making them easy to identify.
Keating Et al 2013 performed a similar test predicting eye colour, hair colour and ancestry
with moderate accuracy, but that’s currently not good enough for court testimonials.
Also, checkout the QOVES facial analysis of Tsunaina and her otherworldly features after
this.
There are a few takeaways from gene research.
Firstly, since we lack insight into the effect of genes on facial morphogenesis, gene mapping
studies should be conducted so that developmental and cell biologists have more information
on which genes to focus on to improve face aesthetic and function.
That being said, heritability studies still show that a large part of your facial attraction
is still determined by your parent’s genetics some of which are completely out of one’s
control such as fetal alcohol syndrome by a negligent mother.
However, it shouldn’t be taken as the cause of one’s aesthetic misfortunes as orthodontists
have shown that facial development is still largely dependent on upbringing with the most
relatable example being mouth breathing which causes a host of serious facial issues.
It would seem that genetics sets the natural bar for how attractive one’s face can be
with predetermined features and facial lengths but lifestyle choices and orthodontic habitus
determine if that potential can even be reached.
To some extent, lifestyle can also influence proportions as explained in the Diet and Teeth
video where tougher, traditional diets led to more handsome jaw widths.
With the unprecedented progress in plastic surgery, one’s genetic potential matters
less and less which goes against the predictions Gattaca made for our dystopian future.
A special thanks to Dr Sony Sherpa for helping with this video.