Buzz
Humans are a fascinatingly odd species, marked by distinct characteristics. In this examination of our evolutionary journey, we explore the intriguing origins behind some of our most perplexing, remarkable, and highly valued human traits. We'll dive into why we blush, how our unique body form evolved from delayed maturation, and uncover the mystery of the human chin.
10. Twitching Upper Lip
We’ve all seen it in action movies or even felt it ourselves when facing that frustrating individual who’s tarnished our reputation with rumors. When angered, humans may experience a slight twitch at the edges of their upper lip, lifting just a millimeter. This twitch isn’t just a minor reflex; it’s an evolutionary remnant that connects us to our more primal ancestors. It signals the beginning of a snarl, a precursor to baring teeth and growling at a threat, much like wolves, bears, and chimpanzees do. For humans, this lip twitch reminds us that despite our “civilized” demeanor, we’re still far from being fully “tame.”
9. Color Vision
Humans are unique among mammals in that they possess color vision, a rare trait mostly found in day-active species like birds, fish, and reptiles, compared to the typically nocturnal mammals. It was long believed that color vision evolved in humans to help with food selection, but recent research suggests that it’s linked to our lack of body hair. Our exposed faces show blood-flow-related skin colors, revealing our emotional states, visible on our face and upper body. For these signals to be effectively understood, color vision is essential. Early humans who developed color vision were better equipped to assess social interactions, avoid dangerous confrontations, or seize mating opportunities.
8. Hair on Head
We’ve all heard the saying, “not a hair on your head will be harmed.” But why does a primate have hair on its head and not the rest of its body? The prevailing scientific view is that humans lost body hair to stay cool, yet retained hair on the head for its crucial insulating and heat-dissipating properties. While an upright biped in the savanna would shed fur, lacking head hair could lead to severe sunburns. Interestingly, humans are not as well adapted to farming as they are to hunting, as agriculture demands bending over, exposing the hairless back. Early humans, however, would have run after prey and gathered food from trees on foot, only briefly stooping to collect plants or small animals.
7. Chin
The chin, often overlooked as a uniquely human feature, is actually found only in humans among primates. As our ancestors evolved larger brains and increased dexterity, we shifted from eating tough, fibrous foods like bony chunks of meat and roots to more delicate foods. Alongside this change came smaller jaws. Some scientists believe the chin evolved as a structural reinforcement to support the jaw, allowing it to remain strong despite becoming smaller. There’s also a theory that sexual selection played a part, with an attractive jawline serving as a sign of strength.
6. Lifting Feet When Scared
When watching a thrilling movie or feeling anxious, some people instinctively lift their feet or try to elevate themselves. While this might seem like a random nervous gesture, it actually makes sense when viewed through the lens of primate biology. Most predators that threaten primates are ground dwellers, which is why many species instinctively climb trees when in danger. Lifting feet is an inherited reflex, signaling a potential threat and the need to get out of harm's way by climbing higher.
5. Full Body Nudity
The absence of body hair in humans has long puzzled evolutionary scientists, but this trait may be more easily understood when considering our environment. Living in the hot, sun-drenched savannah while moving on two legs likely favored a thinner coat of hair that allowed for better perspiration, helping to regulate body temperature in the open grasslands. As humans adopted an upright posture, they were less exposed to the sun, thus avoiding severe burns on the back. The advantage of rapid cooling outweighed the potential drawbacks of exposure to heat or mild cold. Interestingly, humans didn’t lose hair through a reduction in follicles, but rather through thinning of existing hairs. Since intelligence led to the development of clothing, further natural selection for hair growth was no longer needed.
4. Bipedalism
Walking on two legs is one of the most distinctive features of humans, though it is often overlooked. It's also one of the most debated human adaptations. Scientists have proposed several intriguing theories about the origins of bipedalism, and these theories are likely complementary rather than mutually exclusive. One conclusion is that as humans moved from forests into open grasslands, standing upright became essential for scanning vast distances for food and potential dangers. Additionally, being upright made up for the lack of trees to climb for a better vantage point. As humans continued to evolve, the use of arms became more important for spear hunting, a behavior also observed in chimpanzees. Furthermore, being bipedal made it easier to carry vulnerable human infants.
3. Blushing
The human species may be skilled at deception and masking emotions, but oddly enough, evolutionary processes often favor more “honest” signals. Just as birds have evolved crest feather displays to communicate intentions, reducing the need for direct conflict, human skin color changes serve to convey our mood. In uncomfortable situations, we might try to hide our true feelings, but centuries of evolution driven by social interaction may betray us. Scientific research has shown that blushing helps diffuse hostile reactions by signaling that a person feels shame or regret. In tests, sympathy was more often elicited from individuals who blushed compared to those who remained emotionless.
2. Neotony
Humans are often regarded as an advanced species, but how many of us consider that this might be due to evolutionary “brakes” that slowed the development of age? Research suggests that some of our most significant traits, such as our large heads that contribute to our intelligence, stem from the retention of juvenile characteristics. The rounded features of human faces, and the “beautiful” features in many women and “handsome” traits in men, are also the result of evolutionary pressure for these youthful traits, a phenomenon called neotony. A striking example of neotony in the animal kingdom is the Axolotl salamander, a subspecies of the Tiger Salamander that remains in its tadpole form throughout its life.
1. Bacculum
In the sexual evolution of social species, various indicators, like antlers, have evolved to signal an individual’s reproductive fitness. For most mammals, including our close relative, the chimpanzee, the penis is simply a functional reproductive organ. However, in humans, the penis has evolved into a fitness signal, becoming significantly larger relative to body size due to sexual selection based on appearance. Unlike most mammals, humans lack a penile bone, or baculum. Scientists discovered that this absence was crucial, as an erect penis signals health and reproductive fitness. If a bone were present, it would prevent the erection from being a flexible, variable indicator, and instead make it constant, which would reduce its effectiveness. The lack of a bone also allows the penis to shrink when not needed, preventing it from becoming a liability.
