Over the course of our lives, we see our bodies transform as part of natural human development. Our arms, legs, and other bits and pieces may change shape due to new activities, dietary adjustments, or even a surgical procedure. We notice the shift and may - or may not - like what we see. What we don't realize, however, is that evolutionary changes to the human form are continuing to happen.
Signs of evolution in the human body exist from head to toe. They differ by individual, are influenced by one's circumstances and surroundings, and perpetuate questions about the effects of nature and nurture on the physical form. The study of human anatomy continues to incorporate how evolution is transforming our bodies, and it tries to better explain how evolution has very literally shaped us over the centuries. Here are some mind-blowing facts about how our bodies have transformed, and are still doing so.
There's A Network Of Fluid In Your Body No One Identified Until 2018
Unofficially considered an organ, the interstitium was first identified in 2018. As a network of open, fluid-filled spaces, the interstitium replaced what researchers had previously thought was a "wall" of collagen.
The interstitium is found throughout the human body, including in tissues under the skin, in the digestive and respiratory systems, and around the muscles. According to the initial study, interstitium protects the body and produces lymph, the fluid that's essential to immune cell function.
While the interstitium may be new to most humans, there are indications physicians and scientists knew about it for centuries prior to its "discovery." What is new, however, is the composition of the interstitium and the possible role it has in the spread of disease.Mind-blowing body change?
The Human Jaw Is Shrinking - And Has Been For Centuries
When a 2015 scientific study announced that humans once had "an almost 'perfect harmony' between their lower jaws and teeth," the assertion echoed what scholars had been saying for years - the human jaw is shrinking.
In 2011, a study of more than 300 skulls indicated that, as humans became more sedentary, the resulting change in diet - from hunting and gathering to pastoral farming and processed food - caused a decrease in the amount of force required to chew. Over time, the jaw took on a new shape, which has become increasingly problematic for modern humans.
Due to jaw shrinkage, more and more people experience cramped teeth and, in turn, need orthodontic work. Sleep apnea and comparable sleep disturbances are also traced to the change in jaw shape.
One consequence of shrinking jaws is the absence of wisdom teeth. As of late 2020, research indicated more humans were being born without wisdom teeth than ever before. Called a "microevolution," the lack of wisdom teeth has been attributed to "our faces getting a lot shorter... [with] not as much room because of smaller jaws."Mind-blowing body change?
A Knee Bone Almost Disappeared - But It's Making A Comeback
Medical records from 1875 indicate nearly 18% of patients had a small bone in their knee called the fabella (literally "little bean" in Latin). By 1918, that percentage decreased to nearly 11%. One century later, however, as many as 39% of patients have a fabella - but that's not necessarily a good thing.
According to researchers at Imperial College London, the bean-like bone "just causes us problems." As a small sesamoid bone located within tendons, the fabella is present in many individuals with arthritis and inflammation in their knees.
The exact function of the bone isn't clear because, in the words of Dr. Michael Berthaume, "nobody has ever looked into it." He continued:
The fabella may behave like other sesamoid bones to help reduce friction within tendons, redirecting muscle forces, or, as in the case of the kneecap, increase the mechanical force of that muscle. Or it could be doing nothing at all.
The reason the bone is becoming more prevalent, as theorized by Berthaume, involves the larger composition of the human body. With taller and heavier humans, added knee pressure "could explain why fabellae are more common now than they once were."Mind-blowing body change?
Both Sexes Are Hitting Puberty Earlier
While starting puberty earlier seems to be more pronounced in females, there's evidence that both sexes are entering puberty younger than they did during the mid-20th century. According to one study from 2012 (released in 2013), boys in the US were found to hit puberty between six months and two years earlier in 2012 than they did in 2002.
In countries like Norway, a 2020 study found girls are first menstruating about three months earlier than they did a decade ago, while research from India supports evidence of a comparable trend. In the US, drops in girls' age of menarche vary by demographic group, although there is an overall decline.
With the age of menarche at about 12 or 13 (down from 16 or 17 a century ago), CDC researcher Danielle Buttke believes it indicates that exposure to environmental chemicals may be associated with early puberty. Another possibility, and perhaps not separate in nature, is increased childhood obesity.
The causes of early (or precocious) puberty are still being studied, as are the implications. Among the concerns are increased instances of breast cancer, psychological and behavioral risks, and higher instances of teenage pregnancy. As revealed in a 2005 study from the University of Southampton:
For the first time in our 200,000 year history as a species, humans become sexually mature before becoming psychologically equipped to function as adults in society.Mind-blowing body change?