Lots of dogs have eyebrows that stand out (as bushier than or differently coloured from) the surrounding face-fur. This is not just an artefact of the shape of their skull: it is a variation in the way their fur grows, in the exact same relative position as human eyebrows.
I’m told that the function of human eyebrows is to keep sweat out of our eyes. But dogs don’t have sweat glands on their foreheads.
Wikipedia suggests that they are used for communication.
I can accept that a dog with eyebrows could communicate better than (and thus be more likely to produce surviving offspring than) a dog without eyebrows. But I am cynical that this function would produce sufficient selection pressure for eyebrows to develop where no eyebrows were.
Do other animals have eyebrows? Cats, horses, wolves, gorillas?
I can contribute to this part… Yes, cat’s have eyebrows. They are more like mini-whiskers above their eyes though. I think they also function a bit the way whiskers do kind of like feelers, so that, say a cat is stalking a mouse in tall grass, he knows when to close his eyes and won’t get poked in the eye by a weed.
ETA: If you touch the tip of Lenny’s (my cat) “eyebrows”, he’ll squint or close his eye. I think he takes eyebrow sensation to mean: “too close, protect eyeball”.
Good call! I will try this out tonight with my local canine-eyebrow possessor. That may be the answer I was looking for.
He has other such spots on his face (chin, cheeks) - little bushy circles with a few whiskers sticking out. Perhaps eyebrows are just another example of those, with an added communication function.
It seems likely that eyebrows on dogs have a similar biomechanical function to those on humans, i.e. to direct water away from the eye socket. Secondary functions of non-verbal communication are also possible, but dogs and wolves seem to do a lot of communication with mouth positions, tail movement, body stance (crouching, upright, et cetera); I doubt their use in facial expression is much of an impetus with wolves, though emulating human expressions with eyebrows may be an artificially-selected neotenic trait favored in domestic dogs, making them look more like infants.
Dogs might not sweat, but they do go out in the rain, and they’d probably rather not get a bunch of rain runoff in their eyes, either. In fact, a dog without eyebrows probably wouldn’t see as well in the rain, and might therefore have a little less success with hunting, and therefore be selected against. It’s probably not a very strong selection, but then, eyebrows are a pretty simple adaptation, too, without any significant downside.
Don’t know. Had a cat once, who couldn’t resist smelling lit candles. Don’t ask me why, but anyhow I let him do it - you know, if he burns himself he won’t do it again. At least that’s what I thought; instead, around christmas every year he always had his eyebrows half burnt down. Never seemed to bother him. As a matter a fact, he didn’t seem to have noticed when they went pshhh, if it wasn’t for the smell, presumably, which made him look puzzled for a sec or two, and then off he went (only to come back later). But he was a strange fellow. You’re probably right.
