By Nancy Castle

If your organization would like permission to reprint and distribute this article,
please contact the author directly for permission and terms.

No part of this article may be reprinted and/or distributed without the express written permission
of the author, as that is a violation of copyright laws. If any such violations are discovered,
monetary compensation will be expected to be paid to the author!

All photos on this page were contributed by and used here
with the express written permission of the horse owners or photographers.
Do NOT copy these photos.

PRIMITIVE MARKING THEORY

By Nancy Castle ~ Dun Central Station

Introduction:

This paper hypothesizes that the dun gene does not add primitive markings to the coat of a dun dilute colored horse. Rather, the primitive markings are already present in the coat of all horses. However, they are not distinguishable from the coat of most horses because they are essentially "self-colored". They are visually the same color and shade as the rest of the horse's coat at the site of each marking. We can most often see these primitive markings when the horse has a modifier that changes the coat color, but has little to no effect on the primitive markings. The dun dilution gene is the modifier that is most often responsible for visible primitive markings. There are also other modifiers that can cause primitive markings to be visible at times.

I hypothesize that rather than putting the primitive markings on the coat, the dun dilution gene essentially does not dilute the primitive markings that already exist on every horse.

Primitive Markings on Horses:

I first came to the basic conclusion that the dun dilution gene does not dilute the primitive markings of a horse when I noticed that many horses identified as bay based duns had red or red-brown dorsals, while some had black dorsals.

I also noted that on the legs of obvious bay duns, any primitive leg barring that is present within the point of the leg appeared to be black, and any leg barring above the point area appeared to be red or red-brown. If the horse had not been diluted by a dun gene, the area of the leg above the point would have been some shade of red or red-brown. Therefore, the color of the primitive leg bars within the leg point vs. those above the leg point indicated to me that these markings are the same as the base color of the horse. Thus, it appeared that the dun dilution gene was not diluting the primitive leg bars.

Leg Barring on Bay Dun Morab Gelding Note that the upper leg bars are more red or red-brown, while those lower within the leg point are black.

If the dun gene is not diluting the base color at the site of each primitive marking, then a clear bay based horse should indeed have a red or red-brown dorsal stripe, as that is the base color of a clear coated bay along their top line. But why would a bay dun sometimes have a black dorsal and sometimes have only black leg barring, and not both red and black leg barring?

While trying to determine why horses identified as the same base color could have such different colored dorsal stripes, I considered other possible modifiers that are known, on undiluted bay horses, to change the color of the dorsal area of the horse.

Photo Credits

To read the rest, please click the file name below to download the full pdf document.

PrimitiveMarkingTheory.pdf
Approximate file size - 2.2 megs
Comments, feedback, questions? ~ Send Here