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Comment by phyzome | Hacker News Reader

Tangential question: Why do humans place emphasis on bathing, when most other animals don't seem to need to do it? (I think in the US we bathe more than we actually need to, but on the other hand I assume that the strong cross-cultural emphasis indicates that we do actually need to do it to some degree to stay healthy.) Maybe something about our unusual skin, and how we sweat to stay cool?

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A lot of animals bathe/groom. Birds, other primates, cats. Tons of mammals swim as well. Deer, bears, etc (what other animals are there??)

I've noticed that the more I exercise, the cleaner + healthier my skin is. Showers only get me partly there - I need to sweat through a full rinse cycle to get all the funk out.

The only reason our sweat even stinks is because of the way it's metabolized by our skin's microbiome. It turns out if you have AOB (ammonia oxidizing bacteria) they can oxidize our sweat and prevent us from stinking

AOBs are found in soils pretty much everywhere. But they're extremely sensitive and can easily be washed away. In contrast, the particular microbes that have closely evolved alongside us to adapt to our skin microbiome often live several layers deep in our skin. When we take a hot shower or soap up we kill them on the surface but, luckily for our skin's health, they can be replenished. However, the AOBs don't have this deep relationship with us because they are not anaerobic. Instead it's likely that we've evolved to expect a constant influx of soil-based bacteria on our skin

Indeed if you look at any other hairless mammals, one of their favorite things is mud baths. Elephant, pigs, rhinos, etc. We're still learning the full extent of how our skin microbiome plays into our health, but the recent research on the gut-brain-skin axis shows it's likely deeply integrated into our evolutionary past

How many mammals actually sweat? I was surprised to learn that dogs don’t sweat, which seems obvious after the fact

Good question. Human sweat _is_ indeed a pretty unique thing. Many animals sweat (e.g. horses, monkeys, hippos, etc). Some animals actually sorta do sweat but it doesn't play as big of a role in their biology as it does in humans. Dogs and cats only sweat in their paws for example

Humans are some of the weirdest hunters because of our incredible endurance. We're pretty slow creatures. If you're an ungulate that just got hit by an arrow, you can easily run away. But a human can keep following you for hours. Some hunter-gatherer groups will keep a persistent hunt going for up to 3 days

So yeah human sweat probably plays a pretty unique role in our physiology compared to most animals, but sweating is definitely not a uniquely human thing. And it's particularly more common in furless mammals

> I've noticed that the more I exercise, the cleaner + healthier my skin is. Showers only get me partly there

Define "cleaner"? What is not clean about your skin that requires exercise to get clean? After every shower, my skin is just "clean"?

My face skin looks way better with regular exercise. Something about the pores + overall tone. I start to notice a difference after 2 sedentary days, and am repulsed by it after a week+ without exercise. I also get a musk coming from my groin that seems to seep through clothes, and is barely affected by showering.

By sedentary I mean full-on jacked-in to the Matrix, 14 hour days on the computer. Someone with a more balanced life will probably experience it differently.

Agreed. The more I exercise, the better I smell.

Interesting. Exercising has positive effects on me, but my skin seems unaffected. (I certainly believe you, though.)

I think he meant 'clearer'.

showers can't get your funk "out" anyway. or do you mean off?

Cats spend a significant portion of their day grooming themselves, a kind of bathing, that keeps their fur smooth.

A strong reason to bathe is acceptance by others. One of the first things we do for a newborn or someone injured after getting first aid is to clean them up. We want people to respond positively to us, and being clean is a part of that.

I doubt you'll see a dirty newscaster.

ISTR that the Aboriginals in Australia didn't bathe. But what if they encountered a river? Did they wash and then immediately roll in dirt to ward off mosquitos?

Most other animals? Well, most birds bathe. Elephants shower themselves with their trunks. Cats bathe themselves with their tongues, dogs get in the water and then shake themselves dry, and pigs wallow in the mud.

Seems like what makes humans different here is that we use soap.

Animals also use things akin to soap. Birds love to bath in the ashes of a fire, the lye burns parasites, the dust chokes them.

I've watched many a bird do so, after a fire.

Using ashes/lye directly on greasy human skin forms a primitive sort of soap too and isn't unheard of in human hygiene practices. And real fine dusts and grits in general seems pretty common as a method of hygiene for animals and humans alike.

Some animals even rub themselves on ants' nests because formic acid kills bacteria.

A lot of animals use sand - rolls in it or throws it at themselves.

I know it is not the same as soap, but it is an interesting parallel.

Charity to the question, I think it is a good question why we bathe as much as we do. Water animals spend a ton of time bathing, no surprise. Many animals are fine with dust baths, though. And many are severely hampered by being wet. Look up a picture of a wet owl.

Unlike many (but not all) other animals, humans spend considerable time in close proximity to other humans in enclosed spaces. If you are pungent, other people in an enclosed space with you will not appreciate your smell. I've done quite a few multi week hikes with only fresh water bathing (no soap, no deodorant) with others (2-18 other people). During the hikes we are outdoors and although we gather reasonably close (less than 1m, or a couple of feet) around a campfire or common place to eat it isn't often you'd be offended by someone else's smell. At the end of these hikes when we first get back to civilisation and are in an enclosed space again - you bet we suddenly notice how much we stink.

Many humans cross paths with hundreds to thousands of other humans every day and the set of people interacted can have great variability across days. Growing up we were taught at home and in school how important it is to regularly wash your hands. The only other examples of such a high level of social mingling for other species that springs to mind are insects swarms/hives/nests and when there are plagues (mice, locusts etc). Unlike these groups, humans are unique in having a very high degree of share tool use (door handles, public seating for transport, cross walk and lift buttons), so there is a huge potential for cross contamination. Bathing and washing with soap is probably one of the key reasons we are able to live in cities the way we do without regular disease epidemics.

Body oder is an odd one. I saw a sibling post talk about skin biome and I feel that has was more traction than it is credited.

As an example, I can definitely develop body oder. However, it generally takes me longer than the rest of my family. I can do 30 miles on my bike and just need to change clothes. And I basically never use deodorant.

To see this at a notional level, consider that deodorant is not common in Japan.

There was an amusing viral video not long ago about people remembering growing up that they had a bath day. Typically Saturday or Sunday, when they would bathe for the week. This is not that uncommon. Well, was not.

Everyone I’ve ever met who thinks they don’t stink, does.

Certainly not discountable. But the number of folks I've shocked by letting them know I don't use deodorant is rather amusing. They typically think I'm lying.

Edit: more relevantly, the number of times I've seen people complain about how someone must not shower, to then learning that person showers daily, is also amusing. BO is something that has a quick onset for a large number of people.

This is a very interesting point. Indoors is quite different from outdoors.

Not so sure about the disease spread part. Hand-washing was... not particularly universal, not so long ago.

Animals bath or at least groom.

And if you’ve ever hunted you’d know wild animals often stink terribly and have a multitude of health issues ranging from parasites, worms, skin infections, etc.

Humans could get away with minimal bathing as well if they are willing to put up with those things as well.

A lot of animals and birds have a quick dip and groom. There's a water lily pond outside our family home, where in the evening, magpie robins drink and have a dip - sometimes, multiple times.

Most other animals don’t sweat. Also they use smells to communicate and identify each other. We use words and faces.

That said, my bird spends half his day preening and making sure the feathers look good.

Maybe it's an arms race, like with teeth whitening and breast augmentation.

I've never looked into this s aspect of grooming and beauty but after googling it I'm not surprised that someone at The Economist has written about this in the past: https://www.economist.com/free-exchange/2008/12/23/breaking-...

Edit: sorry, paywalled article

Humans are pretty unique in being (relatively) hairless and sweating as our primary method of keeping cool. Sweat invited bacteria and traps dirt. I’m no anthropologist but I’d guess manual bathing became a regular thing when early humans developed these traits.

It's business. Create a market for something that you don't need (and is arguably is bad for you), get people to pay for it, make it a 'norm' via advertising.

All that product that can be sold, to be literally poured down the drain and strip your body off the natural, protective oils and bacteria on your skin and hair.

You should ask the guy at my gym who apparently doesn't shower, and singes my nose hair from 10 feet away.

Honest question: is there any way to tell a stranger they stink, without it being horribly awkward and even inappropriate? Truly, this is a gap in our social customs.

There is no gap, you just tell the person they stink!

Some things are awkward no matter what, mostly because the perpetrator made it so, not you.

Recommend a soap. Talk about how much you like it.

Some people will miss subtle hints and think you're just a weirdo who likes talking about soap. Just tell the truth, as it is. Hey dude, you kinda stink, mind showering more often? Thanks.

Did you actually ever research this viewpoint of “animals don’t bathe”? There are numerous replies proving it wrong, but I’m just curious how you seemingly just made it up and posted it.

Have you? They are still right - most other animals do not in fact bathe.

I’m not saying they manufacture soap and showers, it’s very obvious that they have different ways of bathing. I think most people understood this as self-cleaning, so dust, water, licking, everything.

Bathing requires water. Animals obviously clean themselves but the poster asked about bathing specifically.

https://en.wikipedia.org/wiki/Dust_bathing

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