Why do we have fingernails and toenails?

August 3, 2008 8:06 AM

Fingernails and toenails, why? They are a constant annoyance to keep clipped, and for women to do their polish and stuff.

I'm not a believer in Adam and Eve, if you are, sod off. No offense.

If we evolved similar to monkeys, who as far as I know don't have claws, where in the evolutionary development did we inherit the need for nails, and why. They're too fragile for any sort of primal needs like hunting.

Just curious, and tired of constantly trimming them.

posted by hungrysquirrels to grab bag (23 comments total)

All primates have fingernails. Theories on why.
posted by nanojath at 8:22 AM on August 3, 2008

Basically what nanojath said, we got the from our ancestors, to which they were useful. We still have them because they're not being selected against. They also do have some use though, try picking a dime off of a hardwood floor without fingernails.
posted by borkencode at 8:26 AM on August 3, 2008

I'll add, my moderately controversial post on cladistics, which gets into the discussion of how narrative explanations of "why" certain adaptations occurred may be deceptive. Mostly we don't know why adaptations occurred, the mechanisms of change are lost in history, though the study of DNA may ultimately yield more information on the actual mechanisms of change. The question we can speculate about is, why was this adaptation a successful one? Why is it persistent and ubiquitous?
posted by nanojath at 8:36 AM on August 3, 2008

1. Our evolutionary predecessors found them (nails) useful. Trees, bananas, etc.
2. They're still useful. Mutant human strains born without nails have quickly died out, being unable to open birthday presents decorously, and less capable at scoring mates by soulfully strumming the acoustic guitar.
3. Assuming they're useless (but see above), the tough question is, under what circumstances would they be cast off? I imagine things like nails are more resource-intensive than other evolutionary has-beens, but I'm not certain there's a good theory about which traits get thrown aside -- in circumstances where there's not an obvious tradeoff.

Now, if having nails meant a materially higher risk of cornea-scratching, we'd be typing a lot more softly right now.
posted by Clyde Mnestra at 9:04 AM on August 3, 2008

Fingertips have a lot of very sensitive nerve endings. Fingernails protect these nerve endings.
posted by pluckysparrow at 9:15 AM on August 3, 2008

Maybe our deep primal biological natures know that fingernails can be a useful weapon in a fight. In the one self-defense class I ever took, we were told to use anything at our disposal to distract an attacker, including scratching at his/her eyes with our nails.
posted by SuperSquirrel at 9:32 AM on August 3, 2008

They're useful for many things you don't think about. Try wrapping your fingernails in tape for a few days and you'll quickly see how much utility you get out of them.

1. Relieve itch
2. Peel skins and layers from food
3. Scratch
4. Undo knots
5. Pick up tiny objects
6. Act as a "bumper" for your fingers
7. Nail hygiene is a sign of cleanliness (more of why you still have them as opposed to why you had them to start with)
posted by junesix at 9:37 AM on August 3, 2008

They protect your nerve dense fingertips and toes and provide useful manipulative tools. They also reinforce your finger and toes and give you a better grip. Beyond that, they're tools useful for fine work, slicing things and scoring them. Toenails serve less than our fingers do, but human toes are stubby and not very useful in general.
posted by Phalene at 9:48 AM on August 3, 2008

Among the other apes, mutual grooming is an important social behavior. Fingernails are the tools used to do it. Among other things, they're very useful for getting rid of ticks and lice.
posted by Class Goat at 10:06 AM on August 3, 2008 [3 favorites]

What would you do WITHOUT fingernails? I use mine everyday for sewing, picking up small objects, yesterday the arm fell off my sunglasses and I twisted the little screw back in with my nail, petting my dog, parting my hair, pickin' your teeth...
posted by Acer_saccharum at 10:11 AM on August 3, 2008

Judging by the annual sales of fingernail polish, somebody thinks colored nails are sexy. Not me, but what do I know? In other words, another use for nails is as a sexual attractant.
posted by beagle at 10:18 AM on August 3, 2008

A friend doesn't have them - she was born without fingernails or toenails. She is horribly self-conscious of her fingers and toes, which in place of the nail the nailbeds only are covered by a soft, easily damaged corrugated surface which has no utility at all. Sensitive to hot and cold, easily damaged, she has problems turning the pages of a book and picking up objects on the floor, scratching an itch and doing delicate "fine work" (e.g. computer stuff, household stuff, etc).

She cannot paint her nails or get a manicure. For my sibling's wedding, while the rest of us got manicures, she sat uncomfortably in the corner.

She longs for nails and often hides her hands in public.

For her, the problem is not mainly one of utility, but she feels different and weird and hates being singled out because of it, but the utility factor is important, too: some aspect of the gene that regulates fingernail expression (or lack thereof) also is tied to bone density and bone growth, and a side-effect of this mutation is that she was afflicted with arthritis at a very young age and her bones grew in such a way that her joints often cause her problems. I don't know more details about this, but she has told me that the bone/arthritis thing is tied to her lack of nails.

Long story short: not having nails causes her a lot of grief.
posted by arnicae at 10:42 AM on August 3, 2008 [6 favorites]

In this age of brushes and floss, I guess it shouldn't surprise me more people don't realize how useful nails are for cleaning between the teeth crowded into our so recently shrunken jaws.

As I write, it occurs to me one of forms OCD takes could be seen as an indicator this is one of the things nails are 'for': I have seen three different people wandering the streets over the last few years who pick their teeth so much they've wrecked one of their incisors (and one of them had notably thin hair).

And our tongues are rough partly to be able to do what toothbrushes do too, I think.
posted by jamjam at 11:24 AM on August 3, 2008

The protection of our densely nerved-packed finger tips and improvement of dexterity for fine work (see the afore-mentioned dime on hardwood floor) makes sense to me. Also, I'm an avid cook who frequently wields large, sharp knives after having a few glasses of wine. I cannot count the number of time's I've been glad that a knife that slipped just shaved off a good hunk of nail rather than a good hunk of finger. Also, when said nail hunk is missing, I'm always surprised to see how sensitive the top of my fingertip is. I constantly whack it against stuff that I wouldn't otherwise notice except that it becomes very uncomfortable without the helpful keratin shield.
posted by mostlymartha at 11:43 AM on August 3, 2008

No arguments that they're useful, and thanks for the replies so far, most are interesting.
posted by hungrysquirrels at 11:53 AM on August 3, 2008

"I keep my fingernails long / so they click when I play the piano"
Fingernails
Joe Ely

Fingernails covered by Marcia Ball, who absolutely nails it live, a must-see -- many think it's her song, and it surely could be
posted by dancestoblue at 1:14 PM on August 3, 2008 [1 favorite]

Tobacco pickers, prior to the 20th Century, often grew their thumbnails long, then tempered them over a flame to further harden them, and sharpened the edges. The nails were then used as (literally) handy knives to prune tobacco plants -- or, in brawls, to gouge out an opponent's eyes.

I imagine fingernails are similarly useful to hunter-gather cultures, and that toenails serve to protect the toes in cultures that din't wear shoes.
posted by orthogonality at 1:22 PM on August 3, 2008 [1 favorite]

Don't underestimate what beagle said. There are many, many examples in evolutionary biology of a seemingly silly, useless, energy-sucking appendage having a huge impact on sexual selection. Like this bastard right here.
posted by Cool Papa Bell at 1:28 PM on August 3, 2008

I have really strong curved nails (dad's) as opposed to flat, paper thin with edges that curve out at odd angles (mum's) and they are fucking sweet! What aren't they good for!!
posted by mu~ha~ha~ha~har at 4:37 PM on August 3, 2008

I have a nail fungus that destroys my nail beds. So at any given time I'm missing around 50% of at least one of my finger nails. I'm male so society has not pushed me in the directions of arnicae's friend tho I do have a number of nail hiding habits.

Nails are great as claws or tools but they also reinforce the tip of the finger. The fleshy pad at the end of the finger will flex back if the nail is missing. It doesn't flex very much but it is enough to effect to dexterity. The nail provides a backing between which the fleshy tip of the finger becomes compressed when manipulating an object. When picking up a coin with with the finger tips on fingers with nails but not using the nails, you use the bit of flesh compressed between the coin and the nail providing control and feedback. This allows you to have fingers with variable stiffness tips.
posted by bdc34 at 5:45 PM on August 3, 2008 [1 favorite]

For most of my childhood and young adulthood, I kept my fingernails a bit long...maybe 1/8th to 1/4" past the tip of the finger. Whenever I clip my fingernails down to the correct length, my fingertips always feel a bit naked and I feel like I can't do anything with my fingers anymore. Although longer fingernails do make it a hassle to type.
posted by Deathalicious at 2:27 AM on August 4, 2008

To a certain degree, we can also see that nails are being selected against in the toes. Toe nails grow at a much shorter rate, about 1/4 that of fingers. It seems quite possible that in a few hundred more generations, toenails would be vestigal and even more miniscule, along with the possible disappearance of the little (pinky) toe.
posted by explosion at 11:15 AM on August 4, 2008

As a former nail-biter, I can assure you that nails are tremendous insulators. The fingers with nails that I had bitten back nearly to the quick went numb before my normal-length-nailed fingers barely noticed the cold.

Ergo, nails are also a survival mechanism against frostbite.
posted by IAmBroom at 2:54 PM on August 11, 2008