What Identical Twin Studies Tell Us About Fate vs. Effort in Beard Growth

We covered the clinical details of the Shokravi & Zargham 2024 twin study in an earlier article — the protocol, the measurements, the side effects. This piece is about what the study means.

Because when you strip away the clinical language, this study is about something much bigger than minoxidil. It's about the distance between what you're given and what you do with it.

The Setup: One Variable

Monozygotic (identical) twins. Same genetic code. Same parents. Same upbringing. Same pre-treatment beard density — confirmed by clinical assessment. The researchers verified that both twins started in the same place.

Then one twin — Twin A — started applying ¾ of a cap of 5% minoxidil foam to his face every day. Twin B did nothing.

That's it. One variable. Effort.

What Happened: Month by Month

The Philosophical Implication

In genetics, there's a concept called the reaction norm — the range of possible outcomes for a given genotype depending on environment and behavior. Your genes don't dictate a single outcome. They define a range. Where you land within that range is determined by what you do.

The twin study is a near-perfect demonstration of this concept applied to beard growth. Both twins had the exact same genetic ceiling. Both had the same androgen receptor sensitivity, the same follicle density, the same DHT levels. The only thing that differed was one twin's decision to apply minoxidil for 16 months.

And that decision moved him from one end of his genetic reaction norm to the other.

What This Means for Permanence

There's a secondary implication that's easy to miss: the permanence argument gets stronger with identical twins.

The androgen paradox theory for permanence says that once a vellus hair fully converts to terminal, it becomes sustained by DHT in the follicle — independent of minoxidil. It "graduates" from needing the drug.

In the twin study, both twins have the same androgen sensitivity and the same DHT levels. If Twin A's terminal hairs are being sustained by DHT (as the theory predicts), those hairs should be exactly as stable as Twin B's existing natural beard hairs — because the hormonal environment is identical.

In other words: if your identical twin has a full beard sustained by his hormones, and you grow the same terminal hairs in the same follicles using minoxidil, your hormones should sustain them too. Same hardware, same software.

The Three-Month Dropout Problem

The twin study also documents what may be the most practically important moment in the entire minoxidil beard journey: month three.

Twin A experienced shedding at approximately three months. This is the telogen effluvium phase — the point where minoxidil pushes resting hairs into a new growth cycle, causing temporary shedding before the new, stronger hairs come in.

Community data from r/Minoxbeards consistently shows that month three is when the most men quit. They see shedding, think the drug is damaging their beard, and stop. They never see what comes after.

Twin A pushed through. And the difference between his beard at month 3 and his beard at month 16 was enormous. The shedding wasn't failure — it was the transition. Most men who quit at month 3 are abandoning the process right before the results start.

What the Study Can't Tell You

Intellectual honesty matters. Here's what this single case study doesn't prove:

Sample size of one pair. Twin studies with identical twins are incredibly rare and valuable, but n=1 is still n=1. This case study supports the broader evidence (Ingprasert RCT, Almutairi meta-analysis) — it doesn't replace it.

Long-term permanence is unstudied. The researchers specifically noted that no formal study has tested whether minoxidil-gained beard hairs persist after cessation. The twin study stopped at 16 months of active treatment — it didn't follow what happened after stopping.

Individual variation still matters. The twins had the same genetics, but you don't share genetics with them. Your androgen sensitivity, your sulfotransferase activity, your follicle density — these are your variables, not theirs.

The Bottom Line

The Shokravi & Zargham twin study is one of the most elegant demonstrations of effort vs. genetics in the hair growth literature. Two men started in the same place, one did something, and 16 months later the difference was visible from across a room.

Your genetics are not your destiny. They're your range. Where you land within that range is a choice you make every morning when you either apply the foam or you don't.