Chronotype: Are You A Night Owl Or An Early Bird?

There Is A Gene That Determines Morning And Evening People. Night Owls Exist Even Among Hunter-Gatherers.


You know if you are a night owl or an early bird. This turns out to be genetic. A specific gene has actually been identified: PER3. If you have the longer variant, you are a morning person, and the shorter one is for the night owls.

Why Would There Be Such A Gene. Why Don’t We All Have The Same “Clock”?

Having a variety in a hunter-gatherer tribe would be a strong survival skill. Clearly a marauding nearby tribe would have the maximum advantage by attacking in the middle of the night when everyone was asleep. If everyone slept the same schedule, say 7 PM to 5 AM, the attackers could plan an effective attack. But is half the tribe were night owls and the other half early birds, the “window of opportunity” is shortened. So having such a variety of chronotypes in a tribe would be very desirable.

But Other Things Determine Sleep Patterns As Well

Teens and college students are famous for staying up till 3 AM then sleeping till noon. This is not genetic. Puberty derails the internal clock. And not just us humans! All mammals appear to be afflicted by this. The researchers call this “delayed phase” sleep pattern. The cause is unknown, however, the culprit is rather well known: the hypothalamus.

The Hypothalamus Is The Master Timekeeper


The hypothalamus is an almond sized brain found in all vertebrates from the slimy hagfish (our most ancient vertebrate ancestor) on up. It is a controller. It measures circulating chemicals and neural signal. It controls things as well, secreting chemicals and sending out serve signals.

It gets light information directly from the eyes. It regulates most bodily hormones, and keeps the clocks. It decides when you sleep. It decides menstrual periods, and it decides when you enter puberty.

The hypothalamus thinks we are still hunter-gatherers and manages everything that way. Manages to optimize our survival chances. So it has some very good reason for the “delayed phase” sleep patter

n, but a reason most likely rooted is ancient survival activities. We don’t know what the reason it. We could guess. Perhaps, let the teenagers stay up till 4 AM then sleep till noon. Then there is someone on guard around the clock. No sneak attacks. Or maybe it has to do with something else.

It is known that people raised in an environment with more light enter puberty earlier.

Are There Health Implication to Night Owlry versus Early Birdedness?

The early bird is said to get the worm, and it does indeed seem that early birds are generally chronotype-coffeebetter off. One study revealed that early risers had more “white matter” in their brain, fatty material, the lack of which is associated with depression and impaired cognitive function.

Night owls tend to be abusers too: alcohol, smoking, and drugs.

Body Repaired While You Sleep

Soon after the onset of sleep, Growth Hormone shoots way up, maybe ten-fold over daytime levels, and stays high for the first six hours of sleep. With this 10:1 ratio, we can immediately conclude that any benefit occurs almost entirely during sleep. The primary function is repair of damaged cells. You thought you built muscles in the gym, but you actually do it in your sleep. (Repair of a wound is a different matter entirely. It is locally controlled and obviously immediate.) Some sleeping pills suppress the growth hormone secretion, an undesirable side effect.

A good uninterrupted 9 hours of sleep is probably ideal, but lower amounts—even as low as 7½ hours—are probably OK so long as the quality is there.

If you think of the life of our ancient ancestors you realize, too, that their light driven wakefulness and dark driven sleep still accommodated long sleep cycles whether night owl or early bird so at the practical level in today’s world both types need their sleep during the long night of Winter; whether that means just turning off the lights or living by the coursing of the sun.

Sleep tight!

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