Human life expectancy has doubled in the last few centuries, as medical advances have let more kids reach adulthood and more adults live to a ripe old age. But even as people live longer overall, a new study finds that there remains a gap of three or four years between male and female life expectancy. And that gender gap has barely changed at all, even as we now enjoy life expectancies our ancestors could scarcely imagine.
We don't know why women live longer than men but the overwhelming evidence is that they do. An international team of researchers found that all demographic data for humans past and present, dating back to hunter-gatherer populations in both Africa and South America, show precisely the same gap between men and women. The same also holds true for several monkey and ape species, and that fact suggests the cause is tied up in millions of years of evolution.
"If we know that men in the 21st century can live way longer than women in the 18th century, why haven't they caught up to women?" Duke University biologist and study co-author Susan Alberts told Vocativ. "If we could figure out why there is a difference, we could intervene potentially to mitigate. But we don't know. It's a puzzle."
Alberts speculates as to three possible explanations. One is that men are more likely to take risks that could lead to early deaths. For instance, men smoke and drink considerably more than women — although that gap appears to be decreasing. In non-human primates, this risk-taking behavior is also observed, as males will often violently compete for their potential mates.
Another hypothesis, according to Alberts, is that females have more effective immune systems — either because higher testosterone in males potentially suppress male immunity or as a byproduct of evolution's emphasis on the female reproductive role. "You've got to have a great immune system to have babies," she said.
The final possible explanation lies in primate genetics. Women have two X chromosomes, while men have one X and one Y. In this theory, women live longer because they have a backup X chromosome that can guard against harmful mutations on one of the chromosomes. That's unlikely, however, since one of a woman's two X chromosomes is actually inactive. "Even though we have two X chromosomes, one of them is mostly asleep most of the time," she said.
Whatever the reason, the demographic data tell the same story throughout history, whether it's Swedes in the 18th century, recently freed slaves in Liberia in the 19th century, or modern hunter-gatherer societies of today. The actual life expectancies are very different, but male life expectancy is always shorter in every case. (The sole exception is for the Aché tribe of Paraguay, where all males live slightly longer. However, that difference disappears when you look just at Aché adults, factoring out those who died as children.)
One set of life expectancy data in the study not included in the graphic above is that of all Liberians between 1820 and 1843, because the numbers would quite frankly look like mistakes. When you include Liberians who died before adulthood, the brutally high infant mortality means life expectancy drops to just 2.2 years for women and 1.7 years for boys. That's right: The average Liberian could barely expect to live to see his or her second birthday. Alberts attributed this mind-blowing figure to the fact that the Liberians in this data sample were freed slaves who had returned to Africa, where they found a harsh environment and diseases that their immune systems were ill-equipped to handle.
Yet, even then, when disease and hardship ravaged the Liberian population so that just reaching one's third birthday was a minor miracle, girls still lived longer than boys, and the relative gap in life expectancy was in line with that of all the other human and primate populations. This is indeed a puzzle, and solving it could unlock something buried deep in our evolutionary history.
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5 unhealthy mistakes that make you age faster
5 unhealthy mistakes that make you age faster
1. You aren’t sleeping enough
You’ve heard it a thousand times before — not getting enough sleep is the worst thing in the world for your health, and it can even contribute to diseases later on. You may think you’re fine on the five hours of sleep you got last night, but sleeping too little can do serious damage to your skin, which can make you look way older than you are. According to skin care specialist Annmarie Gianni’s blog, studies have shown those who don’t get quality sleep each night had increased signs of skin aging, including fine lines, uneven pigmentation, and reduced elasticity. For those with acne, getting enough rest is particularly important to preserve a youthful look, as the skin heals when you’re asleep. Start getting at least seven to eight hours per night to ensure youthful skin.
Photo: Shutterstock / Andresr
2. You’re eating too much sugar
Sugary drinks and store-bought cookies aren’t just bad for your waistline, they’ll wreak havoc on your looks. Consuming too much processed, sugary food can make your skin look dull. According to research published in 2013, people with the highest blood sugar levels look older. The study involved more than 600 men and women who had no knowledge of their blood sugar levels. A board was asked to guess the age of participants without knowing anything about them, and those who had the highest blood sugar levels were thought to be older.
And consider you may even feel older from the way refined sugars can sap your energy. If you want something sweet, do yourself a favor and reach for the apple instead of the cookie jar.
Photo: Shutterstock / ARENA Creative
3. You’re always stressed
If you’re constantly thinking about the groceries you need to buy, the clothes you need to wash, and the deadlines at work you need to hit, then it’s time to take a deep breath and relax. Not only can chronic stress ruin your sleep patterns and increase your risk for heart disease, but it can also make you look 10 years older than you actually are. Stress chemicals are released into your body when you’re always anxious, which slowly results in a more aged appearance, says The Huffington Post.
If your job is what’s stressing you out, then you’ll want to practice some meditation and mini desk workouts to lighten your mood. The same story mentions a 2012 study published to the journal PLOS ONE shows your DNA may actually be affected by the exhaustion and frustrations you experience at work. Those who worked more stressful jobs were more affected, the story explains, which can actually increase the risks for cardiovascular disease, diabetes, Parkinson’s, and cancer.
Photo: Getty Images/iStockphoto
4. You’re always crash dieting
If you’re always jumping from diet to diet in the hopes of getting your body to where you want it to be, then it’s best to stop while you’re ahead. Making healthy food choices and exercise are great for wellness, but jumping aboard a crash diet is almost always going to set you up for failure.
These diets can also age you dramatically. According to the Miami Herald, fad eating plans often rob us of essential fats, which our skin needs to help retain moisture. Cutting out food groups is a bad choice, too, because you may not get enough of the antioxidants that protect skin from the sun and other types of damage.
5. You wash your hands and face too much
We all want to have perfect skin and clean hands, but all of that washing can do serious damage to your skin and quickly age you. When it comes to your face, use a gentle cleanser without added fragrance, and this goes for tall skin types. While those prone to acne are likely to reach for the products that have benzoyl peroxide or salicylic acid to keep their skin issues at bay, these ingredients strip the skin and cause severe dryness and irritation that can lead to wrinkles and a dull, aged look. And don’t forget to moisturize, either.
While you may be more concerned with your face than your hands, your hands show signs of aging, too. Daily Express explains washing your hands over and over again during the day dehydrates them, leading to wrinkly, aged skin. If you find your hands are dry and cracked from all of the washing, try massaging them with cream, then slipping on some gloves. The natural heat of your hands and the barrier from the gloves will allow the cream to penetrate deep into the skin, giving you ultra soft skin.