We all know what male pattern baldness - androgenetic alopecia - looks like. It’s higher regular to the point of cliche. It’s causes are pretty well known.
But I can’t find any articles that tell me exactly why the balding stops exactly where it does. Why there? And why should it stop at all? Why not full dome?
Does it stop? Or does it gradually progress to full dome if the person lives long enough, just more slowly in some men who have it than in others?
I don’t understand this part. ???
I’m pretty sure it does stop. I’ve looked at pictures of 100-year-old men and their hair seems to stop no differently than younger men.
Sorry, that should be highly regular. Every man with male pattern baldness looks the same as every other man does (only some have facial hair). It’s a cliche in that it’s become a symbol of a beta male or an intellectual, because real men either have hair or shave their heads. (Or have toupees, like several zillion Hollywood stars.)
I have a cowlick that follows the exact pattern of where my “ring” would be if I had male pattern baldness. It could be something inherent in hair somehow…?
It doesn’t make sense to compare one man’s hair loss to another’s, but only the same man’s hair loss over time. I lost most of the hair that I have lost in my late 30’s. By the time I was 40 I had very thin hair on the top of my head, and pretty much my original amount for the other 2/3 of my head. That is still the case, except that the thin hair on the top of my head has gotten thinner, while the rest has remained much the same (while turning gray then white).
So I concur with OP, by observation, most men who have significant hair loss lose it fairly early, and then it stabilizes and stays much the same for most of the rest of their lives. I could make some guesses as to why, but that’s all they would be.
I’ve had that in my late twenties. It’s not that I was balding; I was developing a circular area of perhaps an inch or so in diameter near one of the temples that had no hair, but otherwise the dome was covered. I went to see a dermatologist who told me it’d go away by itself, and it did; after a few years it was gone. I’m now in my late thirties with full hair, no alopecia areata (as the phenomenon is called), and no signs of balding. I suppose it’s a response to changing levels of hormones around that age.
When it comes to evolution, I think you can only really WAG an answer, since there’s no way to go back and run a variety of control groups who do and don’t go through the same environmental shifts, to figure it which shift caused what change.
One thing that does seem to be true is that some portions of the body have fewer blood vessels coming in. The top of the head is one of these places and, to maintain hair, the body has to stretch them all the way just to maintain some hair. There’s nothing else in that region. Lower down, you have the ears, the spine, various neck muscles, etc. that also need blood flow and where that flow is far less optional. If the body does decide that it’s a PITA to have all these long veins all over the place, reducing the ones that go over the top of the skull is the one best option.
Some other things that seem to be true are that hair loss seems to be triggered by testosterone and, specifically, by a specific subtype of testosterone called dihydrotestosterone that seems to be intended to trigger changes in the body as you age (e.g. spurring your body to start producing hair “down there” when you hit puberty and, later, to start losing hair).
If we think of testosterone principally as a hormone tied to athletic capability then prioritizing blood flow to the muscles - as said above - might be one change it could make. But likewise, we might consider the baldness to be an indicator of strength and so it makes you look more fierce on the battlefield. Men who are bald do tend to look a little more “skullish” than people with a full head of hair so that might be an additional or primary bonus.
Alternately, of we think of testosterone principally as a product of aging and of the body being signaled to morph into its next form, then - again - we might consider blood flow efficiency. You no longer need to look quite as handsome and dashing, with sparkly hair, to catch attention. The plumage is an unnecessary waste of energy.
But another possibility could be something to do with sun exposure. The longer you live, the more likely you are to get cancer and the Sun is the #1 source of cancer-causing rays. The top of your head is probably the one location that is the most strongly hit by the sun’s rays and thus - plausibly - the most location to start forming a cancerous growth if the body doesn’t somehow adapt to it.
Plausibly the shielding effect of the hair is less effective than cutting off blood flow to that area, in terms of making it hard for a cancer to grow? Maybe as people bald and start to get sunburns on the top of their head, they’re more likely to start fashioning hats - which are just more effective than hair?
No idea, just theories.
Yes, same here - balding men don’t all look the same, they have very distinctive levels of baldness.
It’s definitely all about the testosterone. A lot of transmen I know end up with some baldness within a couple of years of taking testosterone, though they were all in their thirties or above when they started, rather than teenagers. Post-menopausal women also experience hair thinning and sometimes balding.
The levels of testosterone and other hormones change throughout the lives of every individual, and every individual reacts differently to them (within a range).
I dunno. Scalp wounds are notorious for bleeding profusely. Nothing like arterial bleeding of course but a lot for a minor wound.
I once stowed some boxes under a basement stair case and on straightening up dinged the top of my head on the tin wall plate for the light switch that was on the end of a 2x2 that brought it in easy reach. “That hurt,” I thought to myself. “Maybe I ought to go upstairs and assess the damage in a mirror.”
Before I was halfway up the stairs I could feel a trickle of blood descending my forehead.
I double-checked. To more accurately say what I said, in persons who are suffering hair thinning on their crown blood circulation is significantly reduced compared to a person with hair. The amount appears to be about half. How circulation on the top of the head compares to other parts of the body or even lower in the head, I’m not certain. Whether all men or just some men have the genetics set up to potentially lose circulation at the top of their head, I am not certain. But, definitely, for men with hair loss, there’s a distinct and location-bound change in circulation.
That said, it’s also not clear to me that head wound bleeding is entirely an issue of relative circulation nor that the phenomenon differentiates appropriately between the “head” and the “crown of the head”, which could be two very different things.
IANAD, so these are reasons for doubt not assertions of fact.
The head has a fairly thin layer between the surface and the bone relative to, say, your thigh. Where there’s more material, in theory, the blood vessels could be deeper and wounds could hold together better. Oh the scalp, any cut is likely to go down through more layers and thus - in theory - more likely to cut through one that carries blood. That cut might be more likely to stay open because it’s less stretchy and meaty.
And again, saying that “head wounds” bleed more doesn’t say anything about the crown of the head. It’s not clear from medical information that they’re talking solely nor even mostly about the crown of the head.
I could also see wounds on the crown of the head simply seeming more obstructive because the flow of blood is more likely to go all directions. A cut on your jaw, for example, will just go down and bloody your collar. A cut on the very tip top could go into both eyes, down the back of the head, over the ears, it would depend on how much you’re moving around and what way you’re leaning your head. The “annoyingness” could give the impression of a worse bleed.
Again, those are hypotheses. A doctor would need to confirm or deny them. I’m just saying why I’m uncertain that we should take the general statement that “head wounds bleed a lot” at face value. (Pun not intended.)
I am sure you have all seen the Norwood Scale (I was about a 5A-5V when I decided to start shaving my entire head, which was about where my father and all my maternal uncles’ hair was (they did not do a full shave):
What @Sage_Rat conjectures could make sense but not exactly sure. I had a mole removed from my scalp a few years ago, about where my hairline used to be on my forehead, but was then clear of hair - bled like crazy, but the dermatologist could have nicked a still active blood vessel up there.
Anyway, I always wore hats when outside as well, so probably not anything I did in my lifetime, but is just something in my genes. I like the evolutionary aspect of the conjecture, tho, if true. The other thing to consider in that context is without hair up top, there is no warning at all when you bash your head into something, so profuse bleeding every time that happens would not be any advantage at all, so smaller/lesser blood flow could make sense in that regard, too.
Given that it’s connected to higher levels of testosterone, where are you getting “beta” and “real men” from?
From reality. Nobody knows or cares about the greater levels of testosterone. When has male pattern baldness ever been a symbol of alpha masculinity?
Samurai?
Alpha / beta terminology is weird. But also, the yappy little dogs? They are never alpha. A true alpha needs no posturing.
My understanding was that you were saying that baldness has NEVER been associated with leadership and manliness.
As your second link indicates, samurai would shave the crown of their head to simulate the end look of male pattern baldness. (Obviously, the ones who went bald one their own could skip the shave.)
So, in at least one commonly known case, a bald crown was associated with leadership and manliness.
I said “male pattern baldness” in every one of previous posts, and I specifically contrasted it to shaved heads. The chonmage is a shaved head.