Why do some animals have symmetrical markings, while others of the same species are asymmetrical? Is there a gene for symmetry?
It’s a trade-off. Symmetry implies health, which gives one a better chance at being selected for mating, but asymmetry improves camouflage, which gives one a better chance at surviving. Since both traits are useful, neither has been lost.
It would help if we knew what species you’re talking about.
Are you talking about an animal like a cat? Where some have very regular patterns (like most stripey cats) and others (like a lot of black and white cats) have the mottled, random look? I would wager it’s a gene thing but hope the experts will have an answer.
The question first occurred to me regarding my cats, but it’s true of quite a few other species as well.
Research on what humans perceive as beauty has shown a strong tendency to favor faces and bodies that are perfectly symmetrical. It is believed to be a sign that the person is genetically healthy and, therefore, good breeding stock.
Having said that, Fortean Time magazine http://www.forteantimes.com published a picture a couple of years ago of a chicken with perfectly symmetrical coloring – brown on one side, and white on the other, with a very clear vertical dividing line.
[Bumping this, hoping to get the attention of an informed Doper]
Spotted cats seem to have a dividing line right down the middle, so a grey spot may stop at the spine and an orange spot, different shaped, might start there, or white may. It’s not all that obvious because often enough both sides of the spine have white coats, for instance, but when you look for it you usually see it. Sort of the opposite of symmetrical.
I have no idea if this color-line division is common to spotted horses, dogs, or cattle.
Wild species don’t have nearly the color variation that domestic ones do, & I’m sure it’s due to the humans selecting and breeding from sports, for the novelty of it. For instance, compare wolf color with dog colors.
Wild cattle relations (buffalo, bison) are mostly all within a narrow range of tawny, but tame cattle can be red with white faces, white all over, spotted, black all over, or even tawny like Guernseys.
Are wild species usually or always symmetrical?
Amusingly, the first cloned cat (named “Copycat” or “cc”) had patterns in her fur quite different from her parent, suggesting strongly that color patterns (in cats, at least) may be partly randomly determined during gestation, presumably because regular symmetrical patterns can be noticed more easily, which becomes a nuisance when your existence depends on stalking and pouncing.
Well, and bugging humans into opening cans for you.
It really showed nothing more than that the cat was female, which is part of the reasons why the researchers did it.
The bodies of female placental mammals aren’t genetically uniform. They are a patchwork of cells that are genetically different. The exact distribution of the different cell types is random. As a result the fur patterns on cats that are dependent on the gentic differences between the cells will be randomly distributed acorss the body.
Nothing to do with the functionming of regular symmetrical patterns. That particular colouration never existed in wild cats, it’'s somehting huamns bred into the species.
AFAIK all wild cats are perfectly synmmetrical.
Presumeably it must have existed to some extent for humans to be able to select for it.
“Copycat”, I like it :).
Doesn’t symmetry also aid certain insects, because their markings look like humongous eyes on their wings, and therefore scare the prey away?
All? Perfectly? I’ll have to ask for a cite for that, since I’ve found pictures of big cats (mostly leopards and jaguars, whose pelt patterns are among the most complex) where small but noticeable left-to-right variations exist.
This is a particularly good jaguar photo, and the flaws in the symmetry are most noticeable in the irregular patterns on the shoulder blades, and down the lower spine with the darker spots on the left. Among more monocolored cats (with the black panther being the most extreme case, I suppose) symmetry wins out over camouflage presumably because camouflage (or at least camouflage involving a lot of colour variation) is not necessary for that particular environment.
Well I did say AFAIK. It seems like they aren;t perfectly symmetrical but they are so close that you need to look carfeuly to see the lack of symmetry.
It may well be a mutation that only developed post domestication.