[at-w]

I'm not super well versed but my understanding is that that's right, with your actual DHT levels being the third variable. There are other non-hormonal causes of hair loss, like alopecia areata, but they're much less common.

DHT damages the hair follicles that are sensitive to it, causing them to grow back thinner after each growth and shedding cycle (which is typically a few years). As a result most men don't have visible hair loss until years after puberty kicks in.

[fy20]

It's interesting because there are medicines that can block DHT or reduce it's effectiveness, but they have other negative side-effects. It's almost like if you have this gene and are a healthy man, you should loose your hair - I wonder what the evolutionary mechanism of that is.

[antegamisou]

None, and in fact it has been proposed that men suffering from AGA, especially if it's early onset, may have something equivalent to polycystic ovarian syndrome in women.

https://pubmed.ncbi.nlm.nih.gov/28711970/

    The occurrence of a genetic background in the etiology of polycystic ovarian syndrome (PCOS) represents the rational basis to postulate the existence of a male PCOS equivalent. Hormonal and metabolic abnormalities have been described in male relatives of women with PCOS. These males also have a higher prevalence of early onset (<35 years) androgenetic alopecia (AGA). 

    Hence, this feature has been proposed as a clinical sign of the male PCOS equivalent. 

    Clinical evidence has shown that men with early onset AGA have hormonal and metabolic abnormalities. Large cohort studies have clearly shown a higher prevalence of type II diabetes mellitus (DM II) and cardiovascular diseases (CVDs) in elderly men with early onset AGA. In addition, prostate cancer, benign prostate hyperplasia (BPH) and prostatitis have been described.

    These findings support the existence of the male PCOS equivalent, which may represent an endocrine syndrome with a metabolic background, and might predispose to the development of DM II, CVDs, prostate cancer, BPH and prostatitis later in life. Its acknowledgment would be helpful for the prevention of these long-term complications.

[mathieuh]

The mechanism of baldness is related to the mechanism of growing a beard isn’t it? For me personally I started going bald in my mid-20s, and since then as I lose hair off the top of my head it seems to reappear on my face. So perhaps it’s just a virility/experience signal.

Maybe in the past the fact that someone had survived long enough to go bald or grow a big beard would signal that they had the skill or hardiness to avoid dying young, which might make them more attractive and likely to pass on the gene.