Early risers are oftenglorified 'there's the well-known saying about the early bird catching the worm, and manyarticles,blog posts,and Reddit threadsabout the benefits of getting up at 4:30 a.m.But if rising early isso good for us, why don't all humans get up at the crack of dawn' or at least try to' Why do some of usconsider ourselvesmorning people(also known as larks) ornight owls'The answer is simple: Everyone has a natural internal clock ' a chronotype or circadian rhythm ' that determines when they're most alertand most sleepy. That means that we're not all meant to be morning people. As chronobiologistTill Roenneberg explains in his book,"Internal Time: Chronotypes, Social Jet Lag, and Why You're So Tired," the internal factors determiningwhen we like to wake up are primarily genetic. The biggest external factor is exposure to light, especially sunlight.Research into chronotypes helps explain why people have natural sleep patterns, how that changes throughout life, the differences incircadian rhythms between men and women, and what we can do to modify our schedules.What's my chronotype'Most of us think of ourselves as morning or night people, but those divisions aren't scientific ' they're just ways of comparing ourselves to one another."Where you define owl or lark is really arbitrary," says Dr. David Welsh, an associateprofessor studying circadian clocks at UC San Diego. Welsh says that if you look at large surveys of populations, you get a normal distribution of chronotypes ' most people have fairly "average" chronotypes, some prefer to get up a bit earlier or later, andsmall groups naturallyrise extremely early or late. There's no line that distinguishesdifferent chronotypes.Your chronotype is more thanafeeling ' it can be verified by measuring your body temperature and the levels of certain hormones in your blood at different times during the day, since those factorsare regulated by our circadian clocks.According to most research on the topic, we have a genetic predisposition for a certain chronotype, but thegenetic factors that cause some people to feel alert and productive earlier versuslater are complex. A number of different genes are involved, many of which are still being discovered.The broad range of human chronotypesalso take several other variables into account.For most of their lives, men have slightly later chronotypes than women.And alongside preferences aboutwhen we go to bed, people also requiredifferent amounts of sleep. Most adults need between seven and nine hours, though some requireslightly more or less, and a tiny number needfar more or far less.Most of our internal clocks also don't match the 24-hour cycle of our planet.Instead, they tend to be a little longer than 24 hours(though some people's clocks are far longer or shorter). Thosewhose internal clocks run short tend to be early risers ' sleep pressure builds up for them more quickly, pushing them to fall asleep earlier and rise with the sun.Roenneberg explains in his book thatthere might be an evolutionaryexplanation for whypeople have such varied body clocks. As humanity evolved, it was probably advantageous for some of us to be more alert at different times of day. That would haveallowed members of groups to stay awake at night in order towatch for predators orhunt for food that was easier to catch in the dark.Thechanges our internal clocks undergo throughout our lifetimes could also be related to this evolutionary legacy.Chronotypes start early for young children, become later in adolescence, then getearlier again as we age.Roenneberg notes that the shift toward a later schedule among adolescents tends to coincide with the time of life at which humans peak in athletic ability ' around 20. The most physically capable people are therefore alsomost comfortable staying awake through the night. (In general, night owls can keep workinglongerin tests that require staying awake for long periods of time.)Today, however, the observed chronotype changes that happen in teenagers have ledmany sleep researchers to suggest thathigh schools should simply start later.How do we reset the clock'Body clocks can be changed ' when someone moves from Los Angeles to London, they eventuallyshift their schedule, after all ' but onlyto a certaindegree. So how much can we adjust our internal clock'"You can't wish yourself to be a morning person if you're really an evening person, but what you can do is alter your light exposure," Welsh says.Daylight naturally helps us feel alert, while darkness prompts the bodyto produce hormones that make us sleepy. That's howwe adjust to new time zones.According to Welsh, thosewho want to start waking up earlier should try toexpose themselves to bright light first thing in the morning for at least half an hour, since early sunlight exposure acts a daily reset.(In experiments where people are kept away from clocks and natural light, internal clocks can run wild.)Maximizing the amount of natural light youget during the rest of the day and avoiding light at night will also help the brain and body adjust to anew schedule.Tomove yourbody clock in the laterdirection (for travel, for example, or if early risers are tryingto sleep in later), Welsh recommends exposing yourself to bright light at night.In a lab, Welsh says, it'susually possible to reset someone's body clock by carefully controlling light exposure, but it can be tough to create that kind oflight exposure schedule in the real world. Plus,certainpeoplesimply find iteasier to adjust theirchronotypes than others do.In some cases, it can beimpossible to totally change our natural inclinations, which is why some people struggle with the daily schedulethat work and school impose. The very fact that most people use alarms to wake up means that for the most part,our days begin before we're biologically awake, according to Roenneberg's book. Either that, or we're simplynot getting enough sleep.SEE ALSO:Biological factors determine whether you're a morning person or night owl ' this scientific quiz tells you where you fit on the spectrumJoin the conversation about this storyNOW WATCH: A sleep doctor reveals why melatonin isn't a sustainable, or safer, sleep aid
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