Have you ever wondered why it’s so painstakingly hard for some people to get out of bed in the morning? Have you ever wondered why others fall asleep so early? The answers, surprisingly, lie in your genetics and how they affect your internal biological clock.

It all stems from the concept of a ‘circadian rhythm’, or the body’s internal clock, which has evolved in many living organisms to help their bodies adapt to the daily cycle of day and night. The suprachiasmatic nuclei (SCN) in the hypothalamus of the brain regulates your clock proteins, coded by ‘clock genes’, which control circadian rhythms. The rise and fall of these clock protein levels control various bodily functions, including when we sleep, hormone secretion, heart activity, and body temperature, creating our biological clock. Clock genes have been found in many organisms, such as humans, fish, and even plants. 

However, “the human circadian rhythm is not exactly 24 hours—it's actually 10 to 20 minutes longer,” and other organisms’ biological clocks are also not exactly 24 hours. Because of this, circadian rhythms need to be ‘resynchronized’ to the 24-hour day regularly. This process occurs through regular exposure to ‘zeitgebers’, or time givers. For most mammals, the strongest of these time givers is light, and variations in this light exposure can create variations in one’s circadian rhythm. Given this, it’s no surprise that blue light has become a major focus nowadays, as artificial light from screens may disrupt the delicate balance of our circadian rhythms.

In addition to regulating your circadian rhythm, genetics also determine your chronotype, which describes whether you are an early person, a late person, or somewhere in between. So, an early type might prefer to wake up at 6:00 in the morning and sleep at 10:00 pm, while a late type might like to wake up at 10:00 am and sleep at 2:00 am. A person’s chronotype varies throughout their life span, with the latest chronotype typically occurring around the age of nineteen. After this point, the chronotype generally shifts to be earlier. Nonetheless, it has been found that people typically become more synchronized with their internal chronotype as they age, as early types tend to become more morning-oriented, and late types preserve their evening preferences.

Age isn’t the only thing that affects your chronotype. One’s circadian rhythm and chronotype are “determined by the complex interplay of an unknown number of genetic and environmental variables”. These include environment, light exposure, season, and even social schedules, but it is difficult to pinpoint the individual effects of each of these on one’s chronotype.

What if the key to productivity isn’t about waking up early or staying up late but rather about aligning with the rhythm your body was designed for? Science suggests that fighting against your natural chronotype can have negative consequences, yet modern life often pressures us to do just that. Perhaps the real challenge isn’t becoming an early bird or a night owl—but instead, finding ways to let our internal clocks guide us toward a healthier, more balanced life.