Seasonal Changes: 4 Ways Humans Adjust To Fall

An obvious indication that fall is setting in is that days become shorter and nights become longer. Subsequently, this alters the behaviors of plants, animals and even humans. Bears begin to hibernate and birds migrate, but what do humans do to adjust to the seasons? A lot, as it turns out. Here are just a few:

Adjust to Light

External factors can greatly influence a person's sleep cycles. For instance, light changes can make it difficult for people to fall asleep because they throw off our internal clock. Humans possess light-sensitive cells in the retinas of their eyes that tell the brain when it's day or night. This is how our body establishes sleep patterns. All of this explains why it's so difficult to work overnight shifts or adjust to twice-yearly regional time changes.

Humans also produce a hormone known as melatonin, which regulates the sleep-wake cycles. Levels of melatonin generally peak at night and dip during the day. That's because melatonin secretion is ultimately governed by our perception of light. People have varying sleep-wake cycles based on their circadian biological clock, which is governed by neurons that respond to light and dark signals. These neurons are located in the portion of the brain known as the hypothalamus. 

Ever hear of the "winter blues?" Well, as temperatures get colder and days get shorter, many human suffer from Seasonal Affective Disorder (SAD). Most people affected by SAD feel depressed, moody or experience a loss of energy beginning in the fall and throughout the winter. Essentially, SAD is triggered by light changes and alterations to one's circadian rhythm or hormone levels. One way to treat SAD is with light therapy. 

Adjust to Color

Seasonal changes even affect how humans perceive color, according to a recent study published in Current Biology. Researchers from the University of York discovered that humans specifically distinguish yellow differently in the winter than in the summer. In general, human eyes interpret four "unique" hues: blue, green, yellow and red. Human eyes register these hues as "pure," while all other colors are simply a mixture of each. Among these hues, yellow stands out as the color definition on which most people around the world can agree –- a consensus that has been dubbed "real" or "unique" yellow.  

In their study, researchers asked 67 men and women in the U.K. to judge when a colored light had reached 'unique yellow' in both June and January. The tests revealed that interpretations of the color varied significantly between seasons. 

"What we are finding is that between seasons our vision adapts to changes in environment," Lauren Welbourne, one of the study researchers, said in a news release. "In York (U.K.), you typically have grey, dull winters and then in summer you have greenery everywhere. Our vision compensates for those changes and that, surprisingly, changes what we think 'yellow' looks like."

Adjust Diets

In the fall, humans tend to bulk up for the winter – just like bears preparing for hibernation who pack on pounds that provide winter warmth and that the body can consume for survival at a time when food is scarce. In general, humans tend to eat heavier foods, like stews and root vegetables, during the fall and winter but the eat lighter foods, like salads and fruits during the spring and summer. Eating this way provides for seasonally appropriate nutritional and energy requirements. Humans also face drier environments during the fall and winter when they need to consume more oil to protect their skin and to avoid dry coughs and constipation.

Adjust to Temperatures 

In the same way that animals grow warmer with thicker furs or tighter feathers, humans tend to layer their clothes in the fall and winter. 

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