I saw my first gray hair when I was 18. I was gray at the temples when I was 30, and fully gray by 50.
I am balding, too but it’s not apparent unless you’re looking from above.
But highly variable - as someone noted, he’s been gray since age 30; someone I worked with in the 1980s had salt-and-pepper hair in his early 20s. We used to joke that every time he told a lie he got another gray hair.
I’m 61 and have a few isolated strands of gray, but otherwise have just one patch of white hair: my “Bride of Frankenstein” patch on the left side of my forehead. It’s gradually widening, but not otherwise expanding. Next time I get my hair colored I may have the stylist block off that bit. I think my mother had more gray at the same age but she always kept it colored. When she was under treatment for cancer, she briefly had what looked like a a pure white crew cut (age 74).
I think my hair may otherwise be thinning a bit, but that’s hard to tell; it’s always been quite thick and still makes a substantial ponytail but I find strands on my comb every day.
Well, that you know of. 
I’m a late fifties male, no signs of balding but if the light catches my hair right I look like I have a slight graying at the temples. Which I understand would put me into the “distinguished looks” category.
Related question: can balding be reversed (aside from transplantation) or do remedies merely slow down the thinning process? Basically, I’m willing to try minoxidil! Anything!
It would be awfully hard for me to have a child and not know it. 
It strange why cells melanocytes die that produce melanin in your hair when people get older.
But melanin in your skin and eyes do not die.
You mean stress causes grey hair and thin hair?
That’s a possible explanation. I think it’s just reverse genetics, you inherit gray hair from your kids.
Thanks for taking that in the spirit given. I’m a smartass and I sometimes forget it doesn’t translate so well to written remarks.
Actually, they do.
But I guess the scary thing is the scientist do not know how to stop cells from dying that produce melanocytes. And so there is no treatment or cure.
I just think the US has a very strange culture the FDA can stop Apple bringing out a smart watch but allow companies to sale creams and gels that say you will have more hair and you will look younger.
Well it is a similar thing with your skin the collagen starts breaking down and dying and your skin is more wrinkled and less elastically. And older people their face, arms and hands are wrinkled and less elastically but really sagging and you look really old.
There is no cream or gels that will increase your melanocytes or collagen. But the FDA allows them to sale products that say they work and they do not work.
Same with the medication that claim to increase melanocytes or collagen. All the ads that claim to make you look younger and yet the FDA and government allow this to happen.
Even scarier. Scientists don’t know how to stop brain cells from dying either.
The FDA isn’t allowed to prevent it. And that can be blamed on the government, Orrin Hatch in particular.
Looks like it some protein. Keep in mind diseases can cause brain cells to die.
Their research groups found that—despite very different causes and symptoms—injury, stroke, Alzheimer’s disease, Parkinson’s disease, and the rare, fatal genetic disorder Huntington’s disease have a shared form of “programmed” brain cell death. The team looked closely at a protein called mitochondrial Apoptosis-Inducing Factor (AIF), a specialized part of a cell outside its nucleus that causes the cell’s programmed death. They knew that when AIF leaves its usual place in the energy-producing mitochondria of the cell and moves to the nucleus, it sparks the carving up of the DNA housed in the nucleus and leads to cell death.
Well smoking or spending a lot of time out side in the sun seems to make the collagen break down and make your skin look very wrinkled and less elastically and look very old.
But I do not think one can spend their life in doors and never leave their house.
Not sure if stress and diet plays a part or not.
Well here is interesting article today that got posted on people who have thin hair or no hair.
It looks like doctors are looking into stem cells that may have better cure or treatment than these creams or gels.
The only thing I do not understand is your hair has millions of hairs so you will need millions of stem cells?
Heh. My husband, who is 20 years my junior, now has more gray hair than I do.
Nitpick: Nobody sales anything.