Epigenetics: Can the Environment Change Resemblance?

What exactly is epigenetics?

Epigenetics studies modifications of gene expression that don't change the DNA sequence itself. It's as if DNA were a book and epigenetics decided which pages get read, which stay closed, and with what "voice".

Main mechanisms:

• DNA methylation: small chemical groups added to DNA that switch certain genes off or on
• Histone modifications: the proteins that package DNA can be modified to make certain genes more or less accessible
• Non-coding RNAs: regulate expression without modifying the genetic code

What modifies your epigenome

Several documented factors modify gene expression over your lifetime:

• Diet: Mediterranean vs ultra-processed diets modify dozens of epigenetic marks
• Chronic stress: releases cortisol, which alters expression of metabolic and ageing-related genes
• Smoking, alcohol: durably modify the epigenetic profile of blood and organs
• Physical exercise: measurable impact on expression of muscle and cardiovascular genes
• Pollution, UV exposure: modify the epigenome of the skin in particular

Which means: two people with the same DNA can have different phenotypes (appearance) depending on their lives. This is exactly what we observe in identical twins who diverge visually with age.

The effect on family resemblance

For resemblance between parents and children, epigenetics plays a subtle but real role:

• A child and parent sharing a lifestyle (diet, sun exposure, climate) will have converging epigenetic marks → reinforced resemblance with age
• A child growing up in a very different environment from the parent (different climate, different diet) will see traits diverge: more or less pigmented skin, different adult height, different ageing
• Parental chronic stress can modify the sperm/egg at conception, passing epigenetic marks to the child — this is transgenerational epigenetic inheritance, still debated but documented

The natural experiment of separated twins

The best evidence comes from studying identical twins separated at birth. Several cohorts (Jim Twins, Minnesota Twins) followed pairs of monozygotic twins raised in completely different environments.

Finding: in adulthood these twins remained visibly very similar (same genetic baseline) but showed measurable differences in epigenetic expression — skin, weight, ageing, certain facial traits.

Conclusion: genetics sets ~70-80% of your appearance, epigenetics handles the rest.

What does this concretely change?

Three practical takeaways:

1. Resemblance isn't fixed at birth. A child who didn't look like a parent at 5 may resemble them strongly at 30, because they've lived through similar things.
2. Your lifestyle leaves a trace. Not just on you, but potentially on your children if you conceive after those choices.
3. Environment shows on the face. Smoking, sun, chronic stress, unbalanced diet leave visible marks distinct from parents — not just ageing, but a direction of ageing.

And AI in all this?

Our Look Like Me LLM Engine measures face geometry at a moment in time — so it captures both genetically inherited traits and current expressions of the genome (which depend on epigenetics).

Concretely: rerunning the test at 5, 20, 40 years gives scores that can evolve significantly. It's not an AI error — it's epigenetics sculpting the face differently at each life stage.