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Vestigiality is the state of being a vestige, or a remnant of evolutionary history. Vestigial structures, also known as vestigial organs, are non-functional features that were fully developed and functional in earlier species but now serve little to no purpose for an organism. They can arise due to gene mutations causing changes in proteins, and they provide strong evidence of common ancestry, helping biologists trace the evolutionary origin of species. Vestigial structures in humans include the appendix, wisdom teeth, the tailbone, and certain muscles such as the orbitalis muscle in the eye, the auricular muscles in the ear, and the palmaris longus muscle in the forearm.
| Characteristics | Values |
|---|---|
| Vestigial structures definition | Non-functional features that were fully developed and functional in earlier species but now serve little to no purpose. |
| Other names | Vestigia, rudimentary structures, or remnants. |
| Cause | Changes in behaviour or environment that decrease the purpose of an organ or body part. |
| Vestigial muscles in humans | Muscles in the ear, platysma, palmaris longus, denominator, plantaris longus, sinus hair muscles, and muscles that cause goosebumps. |
| Vestigial organs in humans | Appendix, coccyx, wisdom teeth, maxillary sinuses, hymen, and whale hind limbs. |
| Vestigial organs in other animals | Wings in flightless birds, non-functional eyes in cave fishes, pelvic bones of whales, and hind limbs of whales. |
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What You'll Learn
Vestigial muscles are evolutionary remnants
Vestigial muscles are indeed evolutionary remnants. Vestigial structures, sometimes called vestigia, rudimentary structures, or remnants, are non-functional features that were once fully developed and functional in earlier species. They serve little to no purpose for the current organism. Vestigial structures can be anatomical, physiological, or behavioural. They are remnants of evolutionary history, providing evidence of evolution and adaptation over time.
In the human body, several muscles are considered vestigial. For example, the platysma is a quadrangular muscle that exists in sheet-like form. It is the vestigial remnant of the panniculus carnosus of animals. While this muscle allows horses to flick flies off their backs, it has no significant function in humans. Similarly, the orbitalis muscle, also known as Muller's muscle, is a vestigial nonstriated muscle of the eye. It forms an important part of the lateral orbital wall in some animals, but its function in humans is unknown.
The human ear also contains vestigial muscles. Humans and other primates such as orangutans and chimpanzees have ear muscles that are minimally developed and non-functional. These muscles cannot move the ear and therefore serve no biological function. Additionally, the human face consists of pockets of air called sinuses, which are considered vestigial. While they have no significant use, they can become infected, leading to sinusitis.
Vestigial muscles can also be found in other species. For example, the palmaris longus muscle, located in the forearm, is vestigial in nature. While it was once important for climbing and hanging from branches, it has minimal function in modern humans. In fact, approximately 14% of the population is born without this muscle, and its absence does not lead to any loss of grip strength.
The presence of vestigial muscles provides valuable insights into the evolutionary history of species. They are reminders of the changes in behaviour, environment, and physiology that have occurred over time, shaping the functionality of various organs and body parts.
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They are non-functional, having lost their original purpose
Vestigial muscles, also known as vestigial structures, are non-functional anatomical features that have lost their original function through evolution. They are remnants of evolutionary history, providing evidence of how species have adapted and changed over time. While these structures no longer serve their original purpose, they may still be present in the body, indicating their vestigial nature.
In humans, several examples of vestigial muscles can be found. One example is the palmaris longus muscle, located in the forearm, which extends from the elbow to the palm of the hand. While this muscle is absent or underdeveloped in many individuals, it served an important purpose in our ancestors for climbing and hanging from branches. Another example is the platysma muscle, which is a vestigial remnant of the panniculus carnosus found in animals. In horses, this muscle allows them to flick insects off their backs, but in humans, it has no significant function.
The human ear also exhibits vestigial features. In humans and certain primates, such as orangutans and chimpanzees, the ear muscles are minimally developed and non-functional. These muscles cannot move the ear and have lost their biological function. However, some individuals can move their ears due to variability in muscle structure. Additionally, the outer structure of the human ear, known as Darwin's tubercle, is found in around 10% of the population and is considered vestigial.
Vestigial structures can also be observed in other species. For instance, flightless birds may have vestigial wings, and cave fishes living in absolute darkness may have non-functional eyes. Similarly, whales, which evolved from four-legged land mammals, possess pelvic bones that no longer serve a functional purpose in their aquatic environment. These structures highlight how species have adapted and evolved, rendering certain features non-functional in their current form.
The presence of vestigial muscles and structures provides valuable insights into the evolutionary journey of different species. While these structures may no longer serve their original purpose, they are reminders of the dynamic nature of biology and the ongoing process of adaptation to changing environments and behaviours.
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Vestigial muscles include the platysma and the palmaris longus
Vestigial structures, sometimes called vestigia, are non-functional features that were fully developed and functioning in earlier species but now serve little to no purpose for an organism. They are remnants of evolutionary history, like "footprints" or "tracks" in Latin. All species possess vestigial features, and more than 100 vestigial anomalies occur in humans. Examples of vestigial structures in the human body include the appendix, the coccyx, and wisdom teeth.
The platysma muscle is a thin sheet-like muscle that lies superficially within the anterior aspect of the neck. Its fibres ascend superomedially over the anterolateral aspect of the neck, attaching to the mandible and the skin and subcutaneous tissue of the lower face. When the platysma muscle contracts, it produces a slight wrinkling of the neck, and a "'bowstring' effect on either side". The muscle is supplied by the cervical branch of the facial nerve and receives arterial blood supply from the submental branch of the facial artery and the suprascapular branch of the thyrocervical trunk. The platysma is vulnerable to neck injuries that may penetrate it, as it is both superficial and thin. It is also important to not damage the platysma muscle to prevent bleeding.
The palmaris longus muscle is a slender, elongated, spindle-shaped muscle that lies on the medial side of the flexor carpi radialis. It is a weak flexor and provides no substantial flexing force that would inhibit movement in the wrist if its tendon were cut and moved elsewhere. The absence of the palmaris longus muscle does not affect grip strength but does result in decreased pinch strength in the fourth and fifth fingers. It is the most common muscle to be absent in the human body, with rates of absence ranging from 10-20% in the general population. The palmaris longus is also variable in form, with several different presentations documented. The muscle is also frequently absent in one forearm (unilateral) or both forearms (bilateral). The palmaris longus tendon is of great importance for surgeons, as it is widely utilised as a tendon graft for the wrist.
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They are found in humans and other primates
Vestigial muscles are non-functional muscles that once served a purpose in an organism's ancestral form. They are remnants of evolutionary history, which can provide insight into the behaviours and environments of a species' ancestors.
Vestigial muscles are found in humans and other primates. In humans, the auricular or extrinsic muscles of the ear are vestigial. These include the anterior auricular muscle, the superior auricular muscle, and the posterior auricular muscle. While these muscles are non-functional in humans, they play a role in sound localisation and the expression of emotion in other mammals. In rare cases, some people can move their ears in various directions, and it is possible for others to gain such movement through repeated trials.
The orbitalis muscle, also known as Muller's muscle, is a vestigial smooth muscle of the eye. While it forms an important part of the lateral orbital wall in some animals, it is not known to have any significant function in humans.
The muscles of the human face associated with whiskers or vibrissae are also considered vestigial. Histological studies of the upper lips of cadavers have found structures resembling these muscles in a small percentage of specimens.
In addition to these muscles, humans possess other vestigial structures, such as wisdom teeth, the appendix, the tailbone, and body hair.
Other primates, such as orangutans, chimpanzees, and gorillas, also exhibit vestigial features. For example, the plica semilunaris, a small fold of tissue on the inside corner of the eye, is vestigial in chimpanzees and gorillas, although it remains functional in other primates. The ear muscles of these primates are also minimally developed and non-functional, similar to those of humans.
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Vestigial muscles provide evidence of evolution and adaptation
Vestigial muscles, also known as vestigial structures or organs, are non-functional anatomical features that have lost their original function through evolution. They are remnants of evolutionary history, providing evidence of past species and their adaptations to changing environments and behaviours.
In humans, for example, the appendix is considered a vestigial organ. Once believed to aid in cellulose digestion, it now serves little purpose and often causes health issues, requiring surgical removal. Similarly, the coccyx or tailbone is a vestigial structure in humans and other tailless mammals. While it no longer assists in balance and mobility, it may still serve secondary functions.
The human ear also exhibits vestigiality. In humans and certain primates like orangutans and chimpanzees, the ear muscles are underdeveloped and non-functional, yet identifiable. Some people can move their ears due to variability in these muscles, but for most, the head-turning ability compensates for the lack of ear movement.
Additionally, the orbitalis muscle, or Müller's muscle, is a vestigial smooth muscle of the eye. While it forms a crucial part of the lateral orbital wall in some animals, it appears to have no significant function in humans. The platysma, a quadrangular muscle in a sheet-like configuration, is another example of a vestigial muscle in humans.
Vestigial muscles in humans also include the palmaris longus, plantaris longus, and denominator muscles. The palmaris longus, found in 93% of people, was once important for climbing and hanging but now has minimal function. The plantaris longus, located on the sole of the foot, was significant for gripping but has reduced in size and function due to modern lifestyles. The denominator muscle in the neck aided in moving the head side-to-side but is now poorly developed.
These vestigial muscles in humans provide evidence of evolution and adaptation, indicating changes in anatomy, physiology, and behaviour over time.
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Frequently asked questions
Vestigial muscles are muscles that have lost their original function and now serve little to no purpose. They are considered evolutionary remnants, indicating a species' behavioural and environmental changes.
The human body has several examples of vestigial muscles, including the auricular muscles attached to the ears, the orbitalis muscle in the eye, and the tiny muscle that causes our hair to stand upright.
Vestigial muscles provide evidence of common ancestry and help biologists trace the evolutionary origin of species. They also offer insights into the behaviours and environments of a species' ancestors.
Vestigial muscles may have evolved to serve secondary functions, ensuring their persistence. In some cases, they may be harmless or have no significant impact on overall functionality. Over time, these structures can degenerate or be repurposed to avoid the consequences of genetic drift or selective pressures.
