There are quite a few evolutionary leftovers that you can still see in your body. Don't let "vestigial structures" cloak your knowledge about their functions.
Human bodies are one of the most complex yet brilliant works of nature. And in the intricately created human body, wounds and infections are a common occurrence. Over the years, it has learnt to adapt and fight off foreign bacteria, germs, and almost everything that makes you ill.
If you break a bone, new cells’ production gets right to work for mending the damage; if you get a cut, platelets stop the bleeding and healthy cells repair the injured cells.
With all the essential organs of our body, we also have some which used to be a working part of the organ system but have become dormant over the years. These are called vestigial organs, as put forth by the naturalist and biologist, Charles Robert Darwin.
Darwin's Influence On Vestigial Organ's Theory
In his work on evolution, Darwin’s theory about the vestigial organs was revolutionary. Robert Wiedersheim, a protégé of Darwin’s, followed the same thought and found 180 vestigial structures in the human body by 1890. In fact, the discovery of vestigial organs propped up as the most substantial evidence of evolution. Darwin said that these organs often testify to the origin of species, in the same way, silent letters in a word give clues to the word’s origin.
These ‘evolutionary leftovers’ are called vestigial structures. These organs no longer serve a purpose, since the body has adapted without their requirement over millions of years. So, while our perfectly crafted body does have all the necessary components, it also contains unnecessary parts.
What Are These Vestigial Organs?
Vestigiality is the retention of some organs during the evolution of genetically defined structures that have lost some ancestral function in a given species. Evaluation of the vestigial organs generally relies on comparison with homologous features, i.e., similar in position and structure in related species.
Many of the vestigial organs that continue to exist in the human body are:
- The tailbone
- Wisdom Teeth
- Palmaris Longis
- Vestigial organs in our ears
- Third Eyelid
- Male Nipples
- Palmar grasp reflex
The most commonly known vestigial organ is ‘appendix’. The ones who do not know what an appendix is, it is the reason for that sudden stabbing pain in your abdomen experienced seldom on waking up.
What Does It Look Like?
The appendix is a thin, pouch-like tissue tube that extends out of the large intestine, connecting the small and large intestines. Our human ancestors were herbivores and insectivores, who evolved into carnivores over million of years. While they needed the appendix primarily for digestive processes, the organ has become redundant today since we do not need to breakdown cellulose in our diet.
As per a Scientific American article, the appendix ‘might’ contribute to building the immunity. It works as a production unit of antibodies and white blood cells. Not just this, it may also contain ‘good’ bacteria’ that is flushed back into the intestine — post dysentery or diarrhoea care benefits from this.
The appendix also contains lymphoid tissues that regulate pathogens. One in twenty people do get their appendix removed. It might have its advantages, but when it gets infected, emergency surgery can save you.
Scientifically called the coccyx, the tailbone serves no purpose in our body after evolving from our similar-to-monkeys-tailed ancestors. The tailbone comprises of 4-5 small vertebrae which merge into one bone. This bone at the end of our vertebral column looks like a tail.
Is it a Tail? Or Just Something Else?
A study in the New England Journal of Medicine analysed the case of a tail in a human baby. The so-called ‘tail’ turned out to be a fleshy outgrowth in the baby’s tailbone area. The weirdest part of this claim was that the outgrowth was not even where a tail should be!
Evolutionists say tailbone it is a useless organ, but it supports organs like the urinary bladder, anus, prostate, and others. It sits at the end of the vertebral column. As a whole, the column supports the head at the top and the organs in the pelvic cavity below.
There would be no support for the urethra, vagina, rectum, and anal canal without the coccyx in place. Some organs pass through the muscular pelvic diaphragm. Coccyx provides firm support that prevents hernia in these organs.
Our ancestors lived on a diet of plants. They needed big molars to chew hard plants. The evolutionary theory states that we outgrew the big molars’ need as humans turned to more heterogeneous dietary options and away from plants. Our heads became smaller and, jaws followed suit.
Wisdom Teeth Are Our ‘Third Molars’
These often pop up in early adulthood, causing immense oral pain of a lifetime. They are removed through surgery; else they end up crowding the rest of the mouth. The human jawbone seldom gets damaged and misaligned if these molars grow out of their way.
Humans have evolved from monkey-like ancestors; the modern-day apes most closely resemble our ancestors. If we can have a tailbone, why not an arm bone that would help us swing from trees? Palmaris Longis is a muscle that runs from the wrist to the elbow.
It is a long muscle running across the forearm’s length (check it out on your hand). It pops out when you touch your thumb and pinky finger. You will see a thin band in the middle of your wrist.
Do you have it?
If yes, you are part of 84% of the human population. Although we no longer swing from trees (clearly), this muscle is useful for medical purposes. It has a function for people who need tendon grafts. Palamaris Longis can be relocated elsewhere as per the need.
Vestigial Parts of Our Ears
10-20% of the human population can wiggle their ears. Are you one of them? Try it out.
You can thank your ‘auricular’ muscles if you can wiggle your ears. Have you seen your pets’ ear swivel in the direction of the opening fridge door? This ability is an evolutionary trait. Humans climbed up the food chain ladder to become apex predators. We no longer have to prick our ears at every slightest sound. We turn our heads to follow the source of sounds, thanks to the flexibility of necks.
Additional Vestige in the Ear
Auricular muscles are not the only vestigial part of the ear. We also have ‘Darwin’s Tubercle’. Touch the topmost part of your ear’s outer rim. You will notice something jutting out. This tenuous thickening helped our ancestors move their ears. But, again, thanks to our newly evolved neck flexibility, we do not need that ability anymore.
A third eyelid is not just a mythological attribute of gods and deities, but it also helped our ancestors survive. Have you observed a little pink thing in the closer-to-nose corner of your eye? Look closer, and you will see a small flap next to it. The name of the small flap is plica semilunaris.
It is a vestigial remain of an organ commonly found in felines, canines, reptiles, and amphibians. It serves the purpose of cleaning particles from eyes as well as moistening them.
An article in the Journal of Anatomy reported a discovery that a vestigial organ named fabella is making a comeback in the human population. It is a small sesamoid bone found in some mammals embedded behind the femur’s lateral condyle.
39% of the human population contains this bone that provides a smooth surface for tendons. This tendon is in the back of the knee. The bone helps reduce friction and stress on the knee put on by the larger calf muscles and shin bones.
This tiny bone started disappearing as we evolved into a taller and heavier species. But records show that it has begun to appear in humans. There is a flipside to the existence of this bone. Fabella leads to uneven force on the knee that, according to experts, can lead to osteoarthritis.
It joins the leagues of tonsils and appendix in things that can be life-saving but end up being dangerous. Some organs and behaviours are vestigial but not quite so.
Human beings are sexless species in the embryonic stage. We are all born with the same genetic footprint. After about six to seven weeks, a gene on the Y chromosome starts processes that develop male infants’ testes.
But the nipples remain where they are. They are not vestigial in the literal sense, as it is not detrimental to have them. We already carry a lot of evolutionary baggage.
Palmar Grasp Reflex
The first experiment everyone does with a baby is to put their finger in the baby’s palm. What follows is a gasp of delight when the baby encloses its whole hand around the finger. Research has found that human babies could hold their weight by relying on the ‘palmar grasp reflex’ for 10 seconds.
Monkey babies can hang on to their mother’s body for more than half an hour on similar lines. The reflex helps babies to cling to their mother’s fur. Humans evolved out of this reflex, and thus, babies lose this reflex around three months of age. This behaviour is not entirely vestigial. Researchers believe it retains vital functions.
Muscle fibres called erector pili cause our hair follicles to stand up. Animals such as cats look bigger when their hair stands straight, to either deter threats or trap air in the fur to maintain warmth in cold weather. But as humans evolved, we shed our initial fur lining.
Human’s Usage of Goosebumps
We still have a minimal layer of hair- the body hair. The assumption is that ‘goosebumps’ (standing straight of body-hair) don’t serve many purposes, given that the human hair is much less in quantity than that of most animals.
The limited energy expenditure used to contract the muscles might induce a tiny release of heat. Since goosebumps are correlated with cold and emotional reactions, they often serve as a means of contact with unusually specific or new activities, like listening to a good song, watching a scary movie, emotions of fear, euphoria or sexual arousal.
Summing it Up
In our understanding of biological science, studies have raised questions over the years about vestigial organs as evidence for evolution. We have to see the meaning of ‘vestigial’ and how these organs might have alternate functions.
Don’t miss the ‘Junk DNA’. Our genetic material revealed during genome sequencing that only a small percentage of our total genetic material of 3 billion base pairs would code for functionality at a rate of 1.2 per cent. Scientists are also discovering profound features of this redundant DNA.
Nevertheless, keep following this space for any new developments in the evolutionary study of vestigial organs, we are sure you’ll only be surprised by whatever new discovery come ahead.