[alancalverd (OP)]

Couldn't help noticing a woman with waist-length hair cycling past me today. Then I began to wonder about the practicality of long hair.

It seems that there is no limit to the length of human hair - surely a unique phenomenon among apes if not all animals?

Now cast your mind back  to the dawn of the genus homo. Gradually becoming bipedal and a collaborative hunter, almost naked except for this extraordinary thatch on top. Assuming the thatch has some protective value, to some extent more is good, and plenty of tight curls not only keep the sun off the brain but also act as a crash helmet. 

So far so good, but the genetic mutations that resulted in caucasian and asiatic versions of homo sapiens also produced hair that just hangs down and gets in the way of everything unless you tie it  up or cut it.   

So which came first - hom sap euroasiaticus, or the knife? We can find flint tools up to about 2,000,000 years old, Which kind of suggests that the northward migration of humans was either prompted or assisted by the evolution of hairdressers, without whom white Man would have been unable to walk very far!

[paul cotter]

You don't have to cut it, just heap it up under a turban as the Sikhs do. As to your more general question, I have no idea.

[alancalverd (OP)]

Turban requires the invention and manufacture of silk or cotton cloth - a lot later than 2,000,000 BC, I think, and it never really evolved in northern Europe. Plaits and ponytails need at least an elastic band. There are plenty of combs and pins around from the Bronze Age onwards, but they don't explain how our pre-paleolithic ancestors managed to get around without tripping over their hair!

[varsigma]

I've seen modern depictions or even forensic reconstructions of Neanderthals and other relatives, with long dreadlocks.

If you don't wash your hair and it's long enough, dreadlocks are the result usually.
But really, the questions should be about why humans became mostly hairless except for the scalp. Maybe something to do with brain evolution, temperature regulation or somesuch.

My theory about becoming hairless and evolving more sweat glands, is that it means you can pursue animals more efficiently, particularly if you're a group of hunters. This adaptation probably emerged well before H. sapiens showed up.

[alancalverd (OP)]

My theory about becoming hairless and evolving more sweat glands, is that it means you can pursue animals more efficiently,

....until you trip over your long head hair!

Neanderthal and "sapiens" (we really need a better word to describe the only species that invents imaginary reasons and ever more efficient methods for killing its own) were familiar with tools, so it is possible that indefinitely long hair is a very recent (less than 2,000,000 years) evolution. Which doesn't explain why!

[Petrochemicals]

After days of painstaking thought and arduous research I think you are neglecting natural factors. Split ends, snagging and abrasion where common hair risks up until recently, for further information contact the scientists at the Garnier Laborotry.

[Bored chemist]

Which came first - knives or Caucasians?
Teeth.

[alancalverd (OP)]

Not the most appetising of meals, and actually surprisingly difficult  to cut with human teeth, which are better at grinding than snipping. Or did our ancestors domesticate the crocodile, beaver or vampire bat before the dog?  You really need a good scissor action.

[varsigma]

I think the original question has to lead to additional questions about human head hair.

Humans are primates; other primates don't have long hair growing from their scalps. Primates and other furry critters have a natural length--individual hairs stop growing and eventually are shed.

The OP is asking why do humans have this, and how isn't it a problem when it gets too long? When did we start grooming each other with knives or hair-cutting tools?

I found this snippet:

Humans and chimpanzees are very similar?genetically, behaviorally, physiologically. Underneath their fur, chimpanzees look sort of like human grandpas (only really, really buff).

But there's one big difference between chimps and humans that is curious once you think about it: Why don't chimps have hair? They have fur, sure, but why don't they have long flowing locks?

--https://www.smithsonianmag.com/smart-news/why-dont-chimpanzees-have-long-luscious-locks-1-180951387/

And why does animal fur seem to always grow to about the same length, while human hair keeps growing and growing?

Here, in a video answering fan questions, BBC Earth Unplugged's Maddie Moate and Simon Baxter explain that when it all comes down to it, human hair and animal fur are really the same thing. Just like chimpanzees, human hair will only grow to a certain length. This is obvious for arm and leg and back and other body hair. But it's also, more surprisingly, true for head hair, too.
Human head hair, like chimp fur, lions' manes and back hair, will only grow to a specific, individually determined length, says Today I Found Out. That length is determined, in part, by the length of your hair's anagen, or growth, phase.

    For the hair on your head, the average length of the anagen phase is about 2-7 years.  For your arms, legs, eyebrows, etc., this phase usually lasts just 30-45 days.  However, in extreme cases which are quite rare, some people have anagen periods for their heads as small as most people?s anagen phases for their arms and legs.  For these people, their hair never naturally grows more than a few inches long, presumably saving them a significant amount of money over their lifetime on barber visits. ;-)  The opposite is also true, with people whose anagen phase can last decades for their scalp hair.  Both of these extremes are very rare though.
 

--ibid

[alancalverd (OP)]

Nice explanation, thanks, but "very rare" needs a bit of qualification. Shoulder-length is common and even waist-length is more of a fashion statement than a freak among young girls.

[Zer0]

Not the most appetising of meals, and actually surprisingly difficult  to cut with human teeth, which are better at grinding than snipping. Or did our ancestors domesticate the crocodile, beaver or vampire bat before the dog?  You really need a good scissor action.

Or perhaps just a rough edged Rock could be Resourceful.

Lay a huge flat stone at the bottom.
Spread the hair on it,
& Strike it with the Rock.

Not sure if They really had Long hair.
But if they did & if a similar technique was applied, They must have had quite an Extraordinary bond of Trust with eachother.

ps - do Barbers have Nightmares of chopping of their customers Ear?

[alancalverd (OP)]

Not nightmares, but insurance.

[Zer0]

Not nightmares, but insurance.

Similar to Financial Insurances, Wish there were Mental & Emotional Insurance policies for sale too.


Like say a Drunk smashed into someone while walking their dog...
Owner survived, pet died.

Financial Insurance shall pay any n all medical reimbursements.
Including a Mental health package which shall Wipe Off all the Bad & Gory Detailed Memories of the incident from the Owner's mind.
& an additional Emotional cover package will ensure the Pet is Cloned & Returned to Owner at the earliest.

ps - Dr Calverd i Hope you are keeping Well n doing Good!
( : & the same for All your Pets too : )

[OokieWonderslug]

I have found hundreds of flint scrapers that could easily cut hair if you tried to. And since flint scrapers are the easiest thing to make I am sure they figured that out over 100,000 years ago.

[Zer0]

I have found hundreds of flint scrapers that could easily cut hair if you tried to. And since flint scrapers are the easiest thing to make I am sure they figured that out over 100,000 years ago.

Very Nice Answer!
Short & Simple.
Great!

ps - & Welcome Back!