Why Do Horses Have Manes?

"The mane is thought to keep the neck warm, and possibly to help water run off the neck if the animal cannot obtain shelter from the rain. It also provides some fly protection to the front of the horse, although the tail is usually the first defense against flies."

-- Wikipedia
I'm not buying it.  I find it implausible that manes would evolve because horses with manes had warmer necks, and that their warmer necks proved to be significant to their reproductive success.  There must be some other reason manes evolved.

But what would that be?

I was thinking sexual selection.  That is, I was thinking manes are like the male peacock's tail.  It provides no survival advantage, but the female peacock's like it. So the females pick the males with the best tails to mate with.  That's what I was thinking.

But then I remembered that both male and female horses have manes. So now I'm thinking sexual selection probably isn't the reason horses evolved manes.

But what is the reason?



  1. LOL. You're asking the wrong person. I'm still marveling that noses evolved to hang my reading glasses on. :)

  2. I'm with you on not buying the Wikipedia take.

    "There must be some other reason manes evolved."
    I'm not sure I agree with you there, at least from the standpoint of reason meaning purpose. I think mutations result in a spectrum of results, from harmful to helpful, and a whole host of benign changes. If there is no net harm to the animal's survival, I can visualize some traits more-or-less being "carried along for the ride."

  3. Doug -- now you've got me wondering why noses evolved as they did!

  4. Wise Fool -- My language was misleading. I did not intend to imply that evolution follows a purpose. I recognize that evolution -- and nature itself -- is without intention and purpose.

    Unfortunately, despite the fact I am fascinated by evolution, I do not feel I completely understand everyone of the mechanisms whereby organisms evolve. I have a pretty good grasp of natural selection. And of sexual selection. But I don't really understand genetic drift. So, I've been wondering if the horse's mane is a result of genetic drift?

  5. Ah, OK. I did completely misunderstand you. Sorry about that! :-) (You know, in my mind I was thinking "surely Paul knows this. I hope I didn't misinterpret something.")

    Good question. I'm not totally up to speed on my equine evolution, but it seems to be my recollection that there are several members of the horse family with manes, such as zebras. But manes also show up well outside of the horse family, such as with giraffes, some camels, and some antelopes.

    With that being the case, I'll make a SWAG (scientific wild-ass guess) and suggest that perhaps manes popped up early in evolution quadruped ancestry, and may have even had a distinct purpose at that time (perhaps, sharp bristles like porcupine for a much smaller animal? or perhaps the mane originally ran the length of the back, and thereby intimidated other animals by making the mane-possessing animal look bigger? who knows?). If so, it could be that the genes for manes linger in the pool of many more beasts than we realize, but they have been "switched off" in the majority of cases.

    We may find out in a few years, when we start getting designer dogs and cats, with manes being an option. :-)

  6. Wise Fool -- now you've got me all excited! First, with your observation that non-equines have manes, too. For some reason I forgot all about that! But given that's the case, my mind is running wild with wondering whether that is, as you speculate, the result of a common ancestor, or whether it is the result of convergent evolution! Obviously, I'm not going to get any sleep tonight.

    The other thing you mention is just as fascinating -- designer cats and dogs! Of course, that's going to happen someday. Given human nature, folks will want to hanker with their pets. I wonder what the designs will be? For instance: Will people someday create bioluminescent cats? The possibilities are endless!

  7. I think a biologist would tell you that manes must have conferred an evolutionary advantage, or they wouldn't be there. Anything that large relative to the size of the animal requires extra energy and materials to produce and maintain. If manes were of no use, horses have been around long enough that they probably would have disappeared.

    The only thing I can suggest as a possible advantage is that it would make it harder for a predator to bite down on the animal's neck. Horses have a natural bucking instinct, which is probably there so that they can get predators off their backs. The back of their necks would be a particularly vulnerable place, since they can't reach that area with their heads or hooves.

  8. I think the predator idea is a good one, Cujo. It would make sense (at least to me) of why manes evolved in several species.

  9. Maybe the mane helps diffuse the horse's endorphins into the air, so they can tell who is in heat.

  10. Just like in us humans, our hair is for covering our head and also protecting from heat. I think that is also the same reason of manes and tails of performance horses. Another thing, I have read before that the tail is the extension of their spinal cord, something like that.


Comments Welcome -- but no flaming. If you wish, you can email me at paul_sunstone@q.com