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If engineers were to design the ideal human body, it would almost certainly be vastly different from what evolution has given us. Evolution hasn't sculpted us into perfect beings but instead crafted a collection of adaptations. While these changes have certainly helped us rise to the top of the food chain, they’ve also come with their own set of challenges. Along the way, we've developed aches, pains, and diseases that are unique to humans among primates.
10. Back Pain
Few ailments are as universally complained about as back pain. Whether it's upper back or lower back discomfort, it's a common struggle, with countless chiropractors offering to fix our misaligned spines. But what’s the real cause? Is it just our bad posture from sitting at desks or improper lifting techniques? While those factors certainly play a role, experts point out that the fundamental structure of our spine is also a major contributor to these problems.
Like their modern ape relatives, our hominid ancestors had shorter, rounder spines when they moved on all fours. Their spines didn't endure as much stress because both the hands and feet helped absorb force, distributing pressure more evenly. However, when humans began walking upright around 4 million years ago, our spines gradually lengthened and took on a more S-shaped curve to help balance our torsos over our hips and feet.
Having a curved spine increases pressure on certain areas of the spine, leading to common issues like slipped discs, lumbar pain, scoliosis, kyphosis (hunched back), and more. In addition, our unique method of walking, with one foot in front of the other and alternating arm movements, creates a twisting motion that over time can wear down the discs between the vertebrae and result in a herniated disc.
No other primate (besides our direct ancestors) experiences such problems.
9. Destined for Obesity
In many ways, the evolution of the human body has become a setback, as it hasn’t adapted to our modern, less active, non-hunter-gatherer lifestyles. For example, our early ancestors never knew when their next meal would come, so the body evolved to store energy in the form of fat for future use. Our bodies became so efficient at fat storage that it is now incredibly difficult to lose weight and virtually impossible to maintain that weight loss over the long term. Unfortunately, in a world where fast food is everywhere and meals are always accessible, our body's ability to store fat is now working against us. This has contributed to the obesity epidemic and the rise of type 2 diabetes.
Although we could prevent weight gain by exercising more and eating healthier from the start, if we overeat and gain excess fat, simply changing our lifestyle may not be enough to shed those pounds and keep them off. Researchers explain that when we lose weight, our bodies release a mix of hormones (including ghrelin, the so-called “hunger hormone”) that alter our metabolism and push us to eat. Additionally, after losing weight, the emotional part of our brains reacts more intensely to food, while the part of our brains that controls restraint becomes less active. Essentially, we crave food uncontrollably, and there's little voice telling us to stop overeating.
However, if our willpower is strong enough and we do manage to lose weight, our bodies will continue their relentless efforts to fight “starvation” and try everything possible to regain the lost pounds. These internal defenses may persist for years, or possibly even for the rest of our lives.
Of course, it's proven that people can lose weight and keep it off, as there are some who have managed to do so. However, scientists argue that these individuals are exceptions to the norm, and to remain slim, they must stay hyper-aware by constantly counting calories, measuring food, working out for hours, and obsessively monitoring the scale. Moreover, individuals who have lost weight naturally burn fewer calories doing the same activities as those who never gained weight, meaning former overweight individuals must exert double the effort to stay thin. Most of us simply don’t have the endurance to maintain this weight battle for the long term.
8. Anxiety Disorders
Remaining in a constant state of “fight or flight” was essential when we lived in nature, constantly running from predators that sought to eat us. But the racing heart, tense muscles, and surge of hormones aren’t nearly as useful when we’re sitting at a desk all day. While many of us try to suppress these responses, they don’t always disappear and may sometimes present themselves as anxiety disorders—at least according to some scientific theories.
As evolutionary biologist Dr. Stephen Stearns explains, many of our bodily responses are remnants from the Pleistocene era, which spanned from 2 million to 10,000 years ago. Even dreams that trigger anxiety, like showing up naked to work or falling off a cliff, might be a result of our Pleistocene brains interpreting night-time as an unsafe period.
For some, the cause of anxiety isn’t so much the suppression of the fight or flight response, but its overuse in every situation (dangerous or not) until it makes us ill. Psychiatrist Randolph Nesse suggests that we perceive danger in normal situations because the fight or flight mechanism hasn’t evolved in sync with our bodies or the world we now live in. For instance, flying in an airplane or walking into a room full of strangers are activities our ancient brains would never have experienced—too risky. Yet, these scenarios are now everyday occurrences. Constantly reconciling our natural instincts with the pressures of society often leads to unease and stress.
7. Knee Strain
Although the knee is highly mobile and well-suited for load-bearing and movement, it remains one of the most frequently injured parts of the body, with around a million knee surgeries performed annually in the United States alone. This is an issue that other primates don't experience to the same extent.
It appears that by evolving to stand upright, we have placed significantly more strain on our lower limbs, with the knees bearing much of the load. In fact, when we run, our knees absorb forces that are several times our body weight. Additionally, due to our relatively wide pelvis structure (another result of bipedalism), our thighbones angle inward toward the knees. This alignment is beneficial for overall balance, as it positions our feet directly under our center of gravity, but it also creates an awkward angle that destabilizes the knee joint, making us more prone to injury.
Women, who have wider hips than men, experience an even more pronounced knee-thigh bone angle, which makes them slower runners and more prone to knee injuries compared to men.
6. Foot Problems
Podiatrists everywhere must be thankful for our shift to walking on two feet, or else they’d be out of business. While this evolution allowed us to stand tall, see long distances, and reach for high fruit, it also led to foot issues like plantar fasciitis, bunions, collapsed arches, and more. These problems are not simply modern consequences of shoes; even ancient bipedal hominids had similar foot issues, as evidenced by fossils.
As we adapted to walking upright, our feet became less flexible and developed arches for support. Still, they often can’t withstand the pressure we place on them, making foot disorders a common occurrence. In addition, the foot contains 26 bones—helpful for grasping tree branches in our distant past, but now those bones make it easier for problems to arise.
As paleontologist Will Harcourt-Smith explained, 'Because the foot is so specialized in design, it has a very narrow window for working correctly. If it’s a bit too flat or too arched, or if it turns in or out too much, you get a host of complications.'
Dr. Jeremy DeSilva compares the evolutionary journey of our feet to a 'jury-rigged' solution, the biological equivalent of paper clips and duct tape. He points out that even the ostrich’s foot is better suited for bipedal walking. However, the ostrich has had 230 million years to perfect its design, while hominids have only been walking upright for about 5 million years. Perhaps in another 100 million years, we’ll have fused ankle and leg bones and only two toes.
5. Lost Opposable Big Toe
Bipedalism not only led to various foot issues but also cost us the ability to have a truly remarkable opposable big toe. While we often take pride in our opposable thumbs, just think of the advantage of having another grasping ‘finger’ on each foot. Had our feet evolved like those of Ardipithecus ramidus (a human from 4.4 million years ago), we would still possess that opposable toe, allowing us to both walk and scale trees. Our gait may seem peculiar by today’s standards, but on the plus side, we would never have to bend down to pick things up again, perfectly matching our inclination for ease and laziness.
That said, the human body is extremely adaptable. Some individuals, like the African pygmy shown in the video, can climb trees (even remarkably slender ones) as effortlessly as a chimpanzee. This requires intense practice from an early age, incredibly strong calf muscles, and flexible feet and ankles. In comparison, the average person would likely break their ankle if they tried to bend their foot the way pygmies do while climbing.
4. Difficult Child Birth
One of the challenges we face due to the transition from a horizontal body structure to an upright one is the extremely difficult child births—especially when compared to other primates. In female apes, the birth canal remains in a fixed position, allowing the baby to exit smoothly in one continuous motion. However, in human females, the birth canal rotates 90 degrees at one point, meaning that women often require assistance to help twist and guide the baby through the twists and turns of the pelvic cavity. Given the complexity of this process and the potential for complications, it's no wonder childbirth was once one of the leading causes of death for women.
Had humans remained quadrupedal, childbirth would likely have been far less hazardous and challenging. It was our habitual walking on two legs that caused our pelvis to shift and narrow, making the process far more difficult.
3. Slower Evolution
Considering the many ways we've become less robust—dumber, weaker, fatter, and plagued with injuries—it’s no shock that we are much slower than our ancestors. Research by anthropologist Peter McAllister reveals that ancient Australians could outrun modern-day Olympians. Based on fossilized footprints found in a claypan lake, McAllister determined that the ancient Australian who made the tracks could run at speeds of at least 37 kph (23 mph)—and this was in muddy conditions and barefoot.
By comparison, the world’s fastest man, Usain Bolt, has achieved a top speed of 41.8 kph (26 mph), but that’s with extensive training, special running shoes, and the benefit of a carefully designed track. If early humans had access to such advantages, they’d likely outpace Bolt by a wide margin.
Although it may seem counterproductive for us to have evolved into being slower, weaker, and less intelligent, the principle of evolution doesn’t always guarantee progress. Our traits can evolve in response to our environment, and what's beneficial in one era or location may not be ideal in another. In our modern, comfortable lives, athletic ability and survival skills may not be essential. However, if an asteroid struck the Earth, sending us back to the Stone Age, our abilities to spend hours at a computer would offer no advantage.
2. Fragile Bones
From a genetic standpoint, our bones aren’t all that different from those of Homo erectus. The downside is that modern bones have about 40 percent less mass, which makes them more vulnerable to fractures and conditions like osteoporosis.
So, why are our bones becoming less dense? It turns out our bodies still have the ability to build strong, thick bones, but our lack of physical activity and the absence of pressure starting from an early age have led us to become a lot softer. This is why doctors frequently recommend resistance training, as it helps increase bone density. For example, the arm bones of professional tennis players (who subject their arms to constant stress) are almost as thick as those of Homo erectus.
Women are especially experiencing bone loss, even when compared to females from just three decades ago. While poor nutrition may play a role, researchers believe that the trend of bone loss began long before the advent of agriculture. Therefore, a lack of physical activity is likely the main factor behind this decline.
1. Shrinking Brains
Contrary to what many believe, the human brain has been shrinking for the past 20,000 years. Although it increased in size during the first 2 million years of our evolution, it has since lost a mass equivalent to that of a tennis ball.
While there is some debate over whether a shrinking brain is inherently a negative development, certain scientists argue it might indicate we're becoming less intelligent. Cognitive scientist David Greary refers to this as the 'idiocracy theory,' suggesting that modern society has created conditions where less intelligent individuals are more likely to survive and reproduce. In contrast, earlier societies, where survival relied on sharp wits, would have seen these individuals fail to survive. As a result, with these less intellectually gifted people staying in the gene pool, our brains have gradually shrunk. Despite technological advancements, Greary believes that much of our progress stems from societal support and maintains that, in terms of natural intelligence, our large-brained Cro-Magnon ancestors may have outpaced us.
On the other hand, some theorists propose that our brain shrinkage is a result of increased efficiency. In this view, to conserve energy, our brains may have downsized to maintain only essential functions, maximizing intelligence while minimizing energy consumption. Another perspective suggests our smaller brains are simply a reflection of domestication and reduced aggression. Proponents of this idea point to bonobos and dogs, whose relatively peaceful natures are associated with smaller brains compared to their more aggressive relatives, such as chimpanzees and wolves.
