Readers reply: what is the evolutionary purpose of toenails?

What, if any, are the evolutionary purpose of toenails?
Gerard Marks

Send new questions to nq@theguardian.com.

Readers reply

Evolution doesn’t produce useless things. But it can get rid of hindrances. Primates don’t need claws. They’re a hindrance to the advanced things we can do with our hands and to walking upright. It was an advantage to have smaller claws, thus smaller claws were selected for. Smaller claws became finger and toe nails. Once they became small, there was no evolutionary pressure for them to be smaller. So they stayed that way. theiguana

I would bet originally they were claws – probably used for climbing trees rather than eviscerating animals on the plains. My sister has one fast-growing big toenail that she refers to as her “velociraptor nail” – a worrying image.

They’re also protective. If you’ve ever lost a toenail, especially a big toenail, for a period of time, and then dropped something on your tender unprotected toe, when the screaming is done you will realise that toenails are still useful! Thomas1178

They were useful for clinging on to our mother’s fur way back when that was a thing. Dan Mulholland

To stop your toes from fraying. LorLala

If you keep the nails sufficiently sharp, either by nature or design, you can scratch the opposing leg and foot while in bed. Keeping five nails in various lengths of sharpness allows you to match the nail with the severity of the itch, thus achieving satisfaction without really moving very much. IbanezJem

For exactly the same reasons as fingernails: digit protection, and occasionally weapons in a duvet fight … kglowe

Toe nails function as shock absorbers for your toes. Consider the force put on the bottom surfaces of your toes as you are running. That force has to go somewhere – and it travels upward. If all you had was soft tissue on the tops of your toes, you would suffer, essentially, a blowout of the soft tissue and pulp. Toenails, which are incredibly tough, act as a covering to keep all that soft tissue in place. I had an unpleasant experience in field hockey that made me aware of the purpose of nails – in this case fingernails. I was struck forcefully on the side of a finger with the hard ball – the OTHER side of my finger experienced a minor “blowout” from the force of that strike. Had I been hit on the soft part of my finger tip, the fingernail would have prevented that from happening. Lillyvanilli

So you can put colourful varnish on them in the summer. Mornex74

They are tasty and add fibre to the diet. MrCassandra

Since we started out as a small mouse-like creature 60 something million years ago, they would have been used for digging, scratching at fleas and fighting. Fast forward, and much of that is still true. Although half of that ancient creature’s feet are now our hands. We didn’t lose our nails because they still protect our toes from minor injuries. Our toes are little sausages of fatty tissue around a small bone. The nail keeps more of the pad below the bone to aid grip (when running or climbing barefoot) and helping with touch sensitivity. But, we are also social beings and, as such, have been decorating our bodies to impress others; this today seems to be the main use for those 10 keratinous canvases. At least for many, when they aren’t hidden in shoes. Alan Bailey, retired podiatrist, Sheffield

Only a nation enslaved to shoemakers would need to question how handy toenails can be. How long has it been since you stubbed your toe? Toenails hold no mystery for barefooted kids running amok. PeterOrmonde

To give the human race something more elevating to think about than Kim Kardashian. Styggron

Because we learned that toeing the line was more civilised than clawing our way to the top. RP Orlando, Westmount, Canada

There is no delete button in evolution … only an eraser. And it works very, very slowly. greeneggsandspam

Google Scholar identified a paper with photos of someone born without toenails. At age 15, the case writeup includes:

“>Anonychia (absence of nails) is a very rare congenital or acquired anomaly. It may occur as a single feature or as part of a syndrome. Nonsyndromic anonychia has been reported in either partial or total forms. Simple anonychia means congenital absence of the nails without any other coexisting major congenital anomaly, and is extremely rare.[1] It is caused due to frameshift and nonconservative missense mutation in the exon 2 of R-spondin 4 gene present on chromosome 20p13, which affects the highly conserved first furin-like cysteine-rich domain that plays a crucial role in nail morphogenesis, resulting in absence of nails.[2]

“Treatment remains masterly inactivity or artificial nails.”

Lack of toenails restricts normal mobility. Unreservedusername

Toenails’ purpose is to rip your socks. Christine Freels

If they were mostly for protection, why not have scales on other parts of your body – you could say that actually they are a vulnerability because they can be ripped off. It seems to me that the nails on your fingers primarily serve as a substrate to the gripping surface on the side of the finger opposite and giving you the ability to pick at and pick up very small things. Our ancestors would have had much more prehensile toes than us and our toenails are probably a evolutionary hangover from when we used our feet differently (hence our little toenails are quite notional now), but they probably serve a useful purpose in stiffening up the front edge of our feet and allowing our toes to gain purchase on things. Paulo777

“What, if any, IS the evolutionary purpose of toenails?” Grammar still matters, along with toenails … Marybeau

The purpose of toenails is to give us back-ache when we trim them. lazysingleton