Baldness: from your mother or your father?

Family dinner. Someone pulls out an old album, and you come across a photo of your mother’s father at 35, already very thin on top. Your own father still has all his hair at 60. So who do you believe? The old saying that “it comes from your mother”, or the mirror showing you your father’s face?

Science has a more nuanced answer than the saying, and a more reassuring one than a coin toss.

The short answer: both

The baldness we’re talking about here is androgenetic alopecia: the common kind, the one that thins the temples and the crown in men and widens the part in women. It comes from hair follicles being sensitive to male hormones, which both sexes have. This sensitivity is largely inherited, and the French Society of Dermatology (SFD) states that it can be passed down from either the mother’s or the father’s side⁵.

DermNet, the New Zealand dermatology reference, says the same: the genes that make you susceptible are inherited from both your mother and your father¹. So it isn’t one or the other. It’s a mix, different for each child.

The X chromosome, the grain of truth

The saying doesn’t come from nowhere. A man gets his X chromosome from his mother and his Y from his father. And one of the genes most closely linked to baldness sits on the X: the gene for the androgen receptor, the “lock” that male hormones act on inside the follicle.

In 2005, a research team showed that variations in this gene were the main factor in baldness that starts early in men. By their calculations, it would play a part in about 46% of early-onset cases². That figure is about early onset, not all baldness.

A large analysis published in 2017 again puts this gene at the top: it’s the clearest genetic signal in the whole study. It also finds 6 regions linked to baldness on the X chromosome, out of 63 in total. The authors write that this could help explain the resemblance often noticed between a man and his mother’s father, while calling it anecdotal themselves⁴.

So yes, your mother’s side counts. But it doesn’t count alone.

Hundreds of genes, from both sides

What recent studies have changed most is the number of genes involved. Baldness isn’t down to a single gene. DermNet talks about several genes, which explains why the age it starts, how fast it goes and the pattern it takes vary from one family member to another¹.

The most telling study was done in the UK on more than 52,000 men aged 40 to 69. The researchers found 287 genetic signals linked to baldness: 247 on the chromosomes you get from both parents, 40 on the X chromosome³. Above all, they measured how much each group weighs.

In other words, in these men, genes from the father and the mother explained about ten times more than the X chromosome: 47.3% against 4.6%³. The authors also note that the X matters much less when baldness starts late than when it starts early³. One limit to keep in mind: the study only included white British men, with a fairly basic question about hair loss³.

Overall, genes weigh heavily. The 2017 researchers point out that the heritability of male pattern baldness is estimated at around 80%⁴: most of the differences between men come from their genes, not their lifestyle.

What about women?

In women, common baldness doesn’t thin the hairline at the front. It thins the top of the head and widens the part. It’s inherited too. The American Academy of Dermatology sums it up simply: the genes come from the mother, the father, or both⁶. DermNet adds that it’s polygenic, meaning it’s passed on through many genes⁷.

It most often starts in your 40s, 50s or 60s, sometimes earlier⁶. It affects about one woman in five by age 40⁵. A woman has two X chromosomes, one from each parent, so the “it comes from your mother” argument holds up even less for her.

Why two brothers don’t lose their hair the same way

Each child gets a different half of each parent’s genes. So two brothers can inherit very different mixes: one thinning at 25, the other barely touched at 50. That’s also why baldness can seem to skip a generation.

The SFD puts it this way: hair loss is often found in other family members, but not necessarily in the generation just before⁵. Genes set up a predisposition. Hormones and time do the rest: hair loss gets more marked with age⁵.

Time counts for a lot. In men, the SFD gives these benchmarks: about 15% of men are affected at 20, 30% at 30, and one in two at 50⁵. DermNet says up to 80% of men by 70¹. A father who keeps his hair at 60 is more the exception than the rule.

Can a genetic test tell you?

You can find tests online that promise to predict your baldness from a bit of saliva. DermNet is clear: predicting baldness with a genetic test isn’t reliable today¹. For women, this kind of test isn’t recommended⁷.

Even the study of 52,000 men, with a score built on hundreds of variants, admits that its predictions for individuals are still rough³. It separates groups of people fairly well. It doesn’t tell you what will happen to you.

Diagnosis doesn’t go through genetics anyway. It’s mostly clinical: a doctor looks at where the hair is thinning, and no blood test is routinely needed for a typical case⁵.

What isn’t inherited

Not all hair loss is inherited baldness. The most common kind of temporary shedding, telogen effluvium, follows a specific event: giving birth, a high fever, an emotional shock. Hair falls out in large amounts two to three months later, then usually grows back within a few months⁸. It has nothing to do with the family album.

The two can look alike at first. If you’re unsure, especially with a family history, a doctor can tell them apart. And if it is common baldness, your doctor can offer you a treatment.

Track instead of guessing

With baldness in the family, it’s easy to start scrutinizing the mirror. The trouble is, the mirror lies a little: the bathroom light, the angle, hair wet or styled differently. One day you see a receding hairline, the next day nothing.

Common baldness moves slowly, over months and years. To see it, you need comparable photos: same room, same light, same distance, dry hair. Aim at the temples, the crown and the part, the areas where it shows first.

That’s what Calvap does. Each week, your last photo appears as a see-through overlay so you can line up in the same spot, and your photos line up on a dated timeline. It shows you whether something is really changing. And if you see a doctor, you bring dated photos rather than a vague impression. Your photos stay on your phone.