Noah Sinclair
Fingernails are flattened versions of claws that have evolved in primates to support broad fingertips. They are made of a tough rigid protein called alpha-keratin, which is also found in the claws, hooves, and horns of vertebrates. While most mammals have claws, humans and other primates are outliers for having nails instead. This is because primates needed broader fingertips for grasping smaller branches while climbing trees and foraging for food. This evolutionary transition from claws to nails has been a mystery to scientists, but new fossil evidence shows that ancient primates had specialized grooming claws as well as nails.
| Characteristics | Values |
|---|---|
| What are flattened fingernails? | Essentially flattened versions of claws |
| Which mammals have flattened fingernails? | Humans and other primates |
| Why do primates have flattened fingernails? | To support broad fingertips, aiding in locomotion and grasping smaller branches |
| What are fingernails made of? | A tough rigid protein called alpha-keratin |
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What You'll Learn
Humans and primates have nails instead of claws
Humans and other primates are unique among mammals for having nails instead of claws. However, the evolution of nails in primates has long been a mystery, with scientists unsure of how, when, and why the transition from claws to nails occurred.
New fossil evidence from Wyoming suggests that the earliest primates had both nails and specialized grooming claws. These fossils belong to Teilhardina brandti, one of the oldest known primates, and date back 56 million years. This finding challenges the previous assumption that the earliest primates had nails on all their digits, indicating that the transition from claws to nails was more complex than initially thought.
Grooming claws are believed to have provided ancient primates with an evolutionary advantage by aiding in the removal of parasites and debris. The presence of grooming claws suggests that early primates may have had more complex social networks and engaged in social grooming. As primates evolved broader fingertips for grasping smaller branches, nails may have become more practical than claws, which could have snagged or gotten in the way during climbing and leaping.
Additionally, the loss of functional claws in primates may have resulted from a reduction in the selective advantages that claws provide over nails. This could be due to an increase in body mass and the associated physiological cost of vertical locomotion. However, the interpretation of the adaptive profile of ancestral primates is controversial, and the exact reasons for the transition from claws to nails in humans and certain primates remain a subject of ongoing research and discussion.
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Ancient primates had grooming claws
Humans and other primates are distinguished from other mammals by their nails instead of claws. However, the question of how and why we transitioned from claws to nails has long been a mystery.
New fossil evidence, however, suggests that ancient primates had both grooming claws and nails. For instance, fossils of Teilhardina brandti, one of the earliest primates, were found in Bighorn Basin, Wyoming, and they displayed evidence of both grooming claws and nails. This discovery challenges the previous assumption that the earliest primates had nails on all their digits.
The shape of the bones at the tips of digits can indicate whether an animal had claws or nails. Bones that support a claw are narrow and tapered, while those that underlie nails are flat and wide. The fossils of Teilhardina brandti revealed bones with these characteristics, suggesting the presence of both claws and nails.
These findings suggest that the transition from claws to nails was more complex than initially thought. The development of nails may have been influenced by changes in primate movement, as claws could have become impractical for climbing, leaping, and grasping. Grooming claws may also have been lost due to more complex social networks and increased social grooming, as they would no longer be needed for self-grooming.
Furthermore, grooming claws may have provided ancient primates with an evolutionary advantage. Thick body hair can harbour ticks, lice, and other parasites, posing health threats and irritation. Thus, having a specialised claw for removing these pests would have been beneficial for ancient primates.
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Nails are a type of claw
The difference between claws and nails lies in their shape. Nails are wide, flat, and shield-shaped, while claws are curved and pointed. The shape of nails and claws is dependent on the bone from which they grow. Bones that support a claw are narrow and tapered, while those that support a nail are flat and wide.
The evolution of nails from claws is linked to the development of opposable thumbs in primates. As our primate ancestors evolved opposable thumbs, which helped them grasp branches and manipulate small objects, claws became less necessary for locomotion. This transition from claws to nails allowed primates to develop broader fingertips, aiding in locomotion and movement across tree canopies.
Nails serve various purposes, including protection for the tips of fingers and toes, and enabling humans to pick up small objects easily. They also serve as a visual representation of a person's health, with nail coloring and texture changes indicating conditions like malnutrition, fungal infections, or skin disorders.
In addition to primates, some other mammals also have nails. For example, ancient primates like Teilhardina brandti had specialized grooming claws as well as nails. Similarly, some living primates like lemurs, lorises, and galagoes have nails on most digits and grooming claws on their second toes.
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Fingernails serve as a health indicator
Fingernails, flattened forms of claws, are one of the features that distinguish primates, including humans, from other mammals. They are believed to have evolved to aid in locomotion, providing a better grip for larger-bodied primates. However, beyond their functional purpose, fingernails can also serve as a health indicator, providing subtle clues about one's overall health.
Nail abnormalities can manifest in various ways, such as changes in colour, texture, or the presence of ridges, spots, or bumps. While most nail issues are harmless, certain conditions can indicate underlying health concerns. For example, white nails, known as leukonychia, can be indicative of several factors, including trauma, anemia, dietary deficiencies, heart or kidney disease, or even poisoning. Similarly, nails with a bluish tint can suggest a lung problem, such as emphysema, or certain heart issues.
The texture of fingernails can also be indicative of specific health conditions. For instance, rippled or pitted nails may be an early sign of psoriasis or inflammatory arthritis. Additionally, dry, brittle nails that frequently crack or split have been associated with thyroid disease, iron deficiency, or repeated wetting and drying of the fingernails. Spoon nails, a condition where the nail appears concave, can also indicate anemia or iron deficiency, and they may affect both fingernails and toenails.
Beyond colour and texture, other nail abnormalities can provide health clues. Horizontal ridges, known as Beau's lines, may suggest kidney disease or other underlying conditions. Black lines on the nails could be indicative of injury, but if they persist or are accompanied by symptoms like inflamed skin, night sweats, or bleeding, further medical investigation is warranted. Small pits in the fingernails can also signal the skin condition psoriasis, and nail biting or picking has been linked to anxiety or obsessive-compulsive disorder.
While these nail abnormalities can offer insights into potential health issues, it's important to remember that they are often non-specific and can have multiple causes. Additionally, nail changes are rarely the first sign of an underlying condition. If you notice persistent or concerning changes in your nails, it is always advisable to consult a healthcare professional for proper evaluation and diagnosis.
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Nails are made of alpha-keratin
Humans and other primates are outliers among mammals for having nails instead of claws. Fossil evidence shows that ancient primates had specialised grooming claws as well as nails.
Nails are made of a strong protein called keratin, which also forms hair and the outer layer of our skin. Keratin provides nails with their toughness and resilience, helping to protect the sensitive tips of our fingers and toes.
There are 54 kinds of keratin in the human body, and they can be divided into two types: Type I and Type II. Of the 54 kinds of keratin, 28 are Type I, and 26 are Type II. Type I keratins consist of acidic, low-weight proteins, while Type II keratins consist of basic-neutral, high-weight proteins.
Within these two types, there are two main configurations of keratin: alpha-keratin and beta-keratin. Alpha-keratin is the type of keratin that makes up human hair and nails, while beta-keratin is found in the scales, feathers, beaks, claws, and fur of animals. These different types of keratin have varying levels of durability and flexibility, depending on their structure.
Alpha-keratin is predominantly found in human nails, providing strength and hardness. It is made up of long chains of amino acids, specifically cysteine, methionine, and phenylalanine, which form a helical structure that gives keratin its strength and rigidity. The nail matrix, or the area where nail growth begins, plays a crucial role in the production of alpha-keratin. This region contains specialised cells that continuously divide and produce keratinocytes, the building blocks of keratin.
The presence of alpha-keratin in nails contributes significantly to their resilience and toughness. The structure and appearance of nails are determined by the amount and arrangement of alpha-keratin within them. Additionally, alpha-keratin can exist as both "hard" and "soft" variants, with the hard version providing more toughness to the tissue.
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Frequently asked questions
No. Only primates have flattened fingernails.
Flattened fingernails are essentially flattened forms of claws. They are protective plates found at the tip of the digits of primates.
Primates have flattened fingernails to support broad fingertips, which help them to climb trees and grasp branches.
No, other mammals have claws, hooves, or talons instead of flattened fingernails.
