You scratch my back, I scratch yours… because that’s why we have nails, right?
Hi guys, Lissette here on Dnews.
So, we get a lot of questions from you on Facebook, on YouTube, on Twitter.
One that got us scratching our heads was Cynthia Gutierrez’s Why Do We Have Nails?
Well…
The truth is scientists don’t really know how our fingers came to have flat, thin covers
made of keratin on them.
All we can say for certain is that we have fingernails because our primate ancestors
had them and they were passed along to us.
For some time, scientists theorized that our nails were simply vestiges of ancestral claws,
but the scientific explanation has gotten a lot messier and more complicated that.
Part of the reason it’s complicated is because nails evolved more than 50 million years ago.
Like most others, this evolutionary trait evolved slowly through natural selection over
a long period of time.
So scientists must rely on cues - like DNA, the physical structure and characteristics
of fossils and bones, and phylogeny - where certain animals fall in the tree of ancestors.
What we do know is that nails on all fingers are an exclusive characteristic of primates
- though similar keratinous structures like hooves and horns exist in other animals too.
The earliest evidence we have of fingernails on primates comes from 55.8 million years
ago, according to a study published in the American Journal of Physical Anthropology.
Researchers discovered that a small lemur like primate, less than six inches long, called
Teilhardina brandti, had nails on its digits - Flat just like ours although they still
retained some claw-like features.
And, like us it was it was an omnivore, but unlike most of us, it spent a good time up
in trees foraging.
They posit that these nails were more useful than claws to these little guys in certain
ways - like helping them hold onto smaller branches - which could mean they would have
been better able to keep their balance a top trees, which would have helped them forage
for food further, and kept them from falling off the tree into the hands...uhhh claws…
of a hungry predator.
The fact that these primates with bodies less than 6 inches long had nails, has seriously
challenged the previous hypothesis that nails evolved as primates bodies got larger.
By pointing out that these nails gave the primates an advantage, this evidence also
challenges the idea that we evolved nails because the rounder, thicker claws simply
became less useful.
Still, it’s important to note that this does not mean nails are categorically better
than claws, just better for certain things for certain primates.
Some researchers have even suggested that the claw to nail relationship is not linear
- that some primates might have lost their claws, evolved nails, and re-evolved claws
again.
But regardless of why we got them in the first place - there are a ton of reasons why we
have them today.
Nails are useful in protecting the skin underneath them and allows us to manipulate small objects
- they can make great little tweezers.
Some scientists also believe they increase the tactile sensitivity of our fingertips.
And they can also serve as health indicators.
For example, yellow nails could be the sign of a fungal infection, which is very common
because some fungus loves to eat keratin.
Yellowing could also signal something more serious like diabetes or lung disease.
And socially, nails have served to indicate status or style for thousands of years - dating
back to the Chinese royalty in 3000 BCE and the ancient Egyptians who differentiated class
by the color they painted their nails.
So while the evolutionary role isn’t clear, it is clear they play an important role in
cultural expression.
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CTA video Have you noticed that the nails on your fingers
grow much faster than the nails on your toes?
Trace and Crystal have the skinny on that here.
Do your nails grow fast or slow?
Mine grow super fast.
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