Evolutionary Flaws Leave Humans Less Than Perfect
June 11, 2018 at 2:42 p.m.
By Max [email protected]
Natural selection implies that random variation, which is key to survival, allows survivors to pass along whatever advantages they may have to their offspring, Homo sapiens, the genus and species we humans belong to. This process has been ongoing for more than 200,000 years which would appear to be enough time to develop our human bodies to function smoothly and effectively.
Every cell, every protein and every letter in our DNA code has also been subjected to the harshness of natural selection over the fullness of evolutionary time. All of that time and all of that selection have resulted in a body form that should be fantastically robust, strong, resilient, clever and mostly successful in the great rat race of life. But it is not perfect.
For example, according to Nathan Lents' new book, “Human Errors,” "We have retinas that face backward, the stump of a tail, and way too many bones in our wrists. We must find vitamins and nutrients in our diets that other animals simply make for themselves. We are poorly equipped to survive in the climates in which we now live. We have nerves that take bizarre paths, muscles that attach to nothing, and lymph nodes that do more harm than good. Our genomes are filled with genes that don’t work, chromosomes that break, and viral carcasses from past infections. We have brains that play tricks on us, cognitive biases and prejudices, and a tendency to kill one another in large numbers."
Our flaws illuminate not only our evolutionary past but also our present and future. One of the major problems is our upright posture. It was adapted from a body plan that had mammals walking on all fours. This tinkering aided our early ancestors, as standing on our own two feet promoted tool use and enhanced intelligence. On the other hand, our backbone has since adapted somewhat to the awkward change; the lower vertebrae have grown bigger to cope with the increased vertical pressure, and our spine is curved a bit to keep us from toppling over. These fixes have resulted into a number of orthopedic problems, particularly as we age.
Bones lose minerals as we continue to grow older, the demineralization makes bones susceptible to fracture and osteoporosis. Spinal disks can slip, rupture or bulge. Muscles continue to lose mass and tone, and weakness contributes to lower back pain. Veins in the legs are more prone to varicosity; they become enlarged and twisted. Valves that should snap shut between heartbeats malfunction, causing blood to pool. Severe varicose veins can lead to swelling, pain and on rare occasions, life-threatening blood clots. Knee joints in particular are somewhat fragile and complicated: Cartilage is worn away with repetitive use, causing bones to grind against each other. The resulting pains may be exacerbated by osteoarthritis.
Another orthopedic problem stems from humans having a relatively short rib cage, which does not fully protect our internal organs.
According to an early article in Scientific American, a number of anatomical fixes are needed to improve our overall well-being. Examples include having a forward-tilting upper torso to relieve pressure on vertebrae. A curved neck with enlarged vertebrae would counterbalance our tilted torso. Leg veins should have more check valves to combat varicose veins. Having knees that bend backward would make bones less likely to grind and deteriorate. Thicker vertebral disks would resist destructive pressures, and thicker bones would protect against breakage during falls.
Various parts of the face, head and neck are other considerations with aging or before. For the latter, we are unfortunate to have a common upper passageway for food and air. When food travels toward the esophagus, a flap-like tab of cartilage (the epiglottis) closes off the trachea, or windpipe. A progressive loss of muscle tone with age decreases the tightness of the seal, raising the risk of inhaling food or drink. There is a weak link between the retina and the back of the eye. This frail connection exists in part because the optic nerve, which carries visual signals from the retina to the brain, connects to the retina only from the inside of the eye, not from the back. Fixes could include attaching the optic nerve to the back of retina, and raising the trachea would help food and drink bypass the windpipe more effectively.
Unfortunately, it is unlikely that evolution will fix our inherent flaws, and future generations must continue to live with them.
Max Sherman is a medical writer and pharmacist retired from the medical device industry. He has taught college courses on regulatory and compliance issues at Ivy Tech, Grace College and Butler University. Sherman has an unquenchable thirst for knowledge on all levels. Eclectic Science, the title of his column, will touch on famed doctors and scientists, human senses, aging, various diseases, and little-known facts about many species, including their contributions to scientific research. He can be reached by email at [email protected].
Natural selection implies that random variation, which is key to survival, allows survivors to pass along whatever advantages they may have to their offspring, Homo sapiens, the genus and species we humans belong to. This process has been ongoing for more than 200,000 years which would appear to be enough time to develop our human bodies to function smoothly and effectively.
Every cell, every protein and every letter in our DNA code has also been subjected to the harshness of natural selection over the fullness of evolutionary time. All of that time and all of that selection have resulted in a body form that should be fantastically robust, strong, resilient, clever and mostly successful in the great rat race of life. But it is not perfect.
For example, according to Nathan Lents' new book, “Human Errors,” "We have retinas that face backward, the stump of a tail, and way too many bones in our wrists. We must find vitamins and nutrients in our diets that other animals simply make for themselves. We are poorly equipped to survive in the climates in which we now live. We have nerves that take bizarre paths, muscles that attach to nothing, and lymph nodes that do more harm than good. Our genomes are filled with genes that don’t work, chromosomes that break, and viral carcasses from past infections. We have brains that play tricks on us, cognitive biases and prejudices, and a tendency to kill one another in large numbers."
Our flaws illuminate not only our evolutionary past but also our present and future. One of the major problems is our upright posture. It was adapted from a body plan that had mammals walking on all fours. This tinkering aided our early ancestors, as standing on our own two feet promoted tool use and enhanced intelligence. On the other hand, our backbone has since adapted somewhat to the awkward change; the lower vertebrae have grown bigger to cope with the increased vertical pressure, and our spine is curved a bit to keep us from toppling over. These fixes have resulted into a number of orthopedic problems, particularly as we age.
Bones lose minerals as we continue to grow older, the demineralization makes bones susceptible to fracture and osteoporosis. Spinal disks can slip, rupture or bulge. Muscles continue to lose mass and tone, and weakness contributes to lower back pain. Veins in the legs are more prone to varicosity; they become enlarged and twisted. Valves that should snap shut between heartbeats malfunction, causing blood to pool. Severe varicose veins can lead to swelling, pain and on rare occasions, life-threatening blood clots. Knee joints in particular are somewhat fragile and complicated: Cartilage is worn away with repetitive use, causing bones to grind against each other. The resulting pains may be exacerbated by osteoarthritis.
Another orthopedic problem stems from humans having a relatively short rib cage, which does not fully protect our internal organs.
According to an early article in Scientific American, a number of anatomical fixes are needed to improve our overall well-being. Examples include having a forward-tilting upper torso to relieve pressure on vertebrae. A curved neck with enlarged vertebrae would counterbalance our tilted torso. Leg veins should have more check valves to combat varicose veins. Having knees that bend backward would make bones less likely to grind and deteriorate. Thicker vertebral disks would resist destructive pressures, and thicker bones would protect against breakage during falls.
Various parts of the face, head and neck are other considerations with aging or before. For the latter, we are unfortunate to have a common upper passageway for food and air. When food travels toward the esophagus, a flap-like tab of cartilage (the epiglottis) closes off the trachea, or windpipe. A progressive loss of muscle tone with age decreases the tightness of the seal, raising the risk of inhaling food or drink. There is a weak link between the retina and the back of the eye. This frail connection exists in part because the optic nerve, which carries visual signals from the retina to the brain, connects to the retina only from the inside of the eye, not from the back. Fixes could include attaching the optic nerve to the back of retina, and raising the trachea would help food and drink bypass the windpipe more effectively.
Unfortunately, it is unlikely that evolution will fix our inherent flaws, and future generations must continue to live with them.
Max Sherman is a medical writer and pharmacist retired from the medical device industry. He has taught college courses on regulatory and compliance issues at Ivy Tech, Grace College and Butler University. Sherman has an unquenchable thirst for knowledge on all levels. Eclectic Science, the title of his column, will touch on famed doctors and scientists, human senses, aging, various diseases, and little-known facts about many species, including their contributions to scientific research. He can be reached by email at [email protected].
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