What’s the scoop?
At some point in our lives, especially when we are younger and more curious, all of us ponder this question. Many of us settle for an answer that is directly tied to racial preference. Stephen Jay Gould, in his essay “How the Zebra Gets Its Stripes,” states that “most African people regard zebras as black animals with white stripes,” whereas I, a typical white American, have always intuitively perceived zebras as white animals with black stripes.
Although the question is a tough one to answer, and one that many people will answer with “Can’t the black and white stripes just coexist in harmony?”, a better, scientific answer must exist somewhere. Race and cultural context have no place in science.
Warning! Scientific Content:
First of all, what is a zebra? Anyone will notice that they closely resemble horses or donkeys, but only a little more “exotic.” In truth, zebras are one of the oldest members of the family Equidae, the “horse” family. The main species that are around today are: Grevy’s Zebra, the Mountain Zebra, and the Plains Zebra, shown in the top row of the picture below. On the bottom row are an extinct descendant of Plains Zebras, called Quagga, which Darwin refers to many times in his work.
A zebra’s stripes form during the early embryonic stages of its life. In other words, a normal zebra is born with stripes, so we cannot use the argument that, say, if it is born all black and forms white stripes during maturation, a zebra is black with white stripes.
I learned once upon a time that zebras are white with black stripes, because a zebra’s underbelly is white. This, however, is not very good evidence, because many animals that are not necessarily white have white or lighter underbellies. As Gould states in his essay mentioned above, “mammals do not have their colors painted on a white background.”
Let’s first of all examine how dark color and pigmentation occur in mammals. Most of it is due to melanin, a pigment made of smaller component molecules and deposited by melanocytes in the bottom layer of the skin. As seen in humans, the amount of melanin deposited into your skin or hair, if any, can be regulated by gene expression.
If the genes activate the deposition of melanin, the fur will be black or brown, and if the genes inhibit the deposition of melanin, the fur will be white. So, in order to get to the bottom of the issue, we must instead ask: do a zebra’s stripes result from the inhibition or deposition of melanin?
From the Teratology Perspective
Teratology is the study of physiological abnormalities during the life history or development of an individual. We can use this field to our advantage, because an abnormality in zebra development can point to what is the “default” setting of the animal.
Jonathan Bard, who proposed “a unity underlying the different zebra striping patterns” in 1977, uncovered an abnormal zebra that had rows of dots and blotches, rather than stripes of color. The spots are white on a black background.
From this evidence, we can hypothesize that a zebras stripes are formed from the inhibition of melanin and that the “default” color of a zebra is black. In other words, a zebra is black with white stripes.
From the Evolutionary Perspective
As stated above, we know that zebras are closely related to horses. Jim Loy points out that “rarely a horse will have faint stripes. From what I can find, only dark horses, never white horses, sometimes have stripes.” Again, this points the way to a black zebra with white stripes.
But what is the point of a black zebra evolving white stripes, you ask? Let’s think about what the stripes do for a zebra. The white of the zebra keeps the animal’s body temperature much lower in the scorching African sun. Therefore, if zebra ancestors were all black and a mutation for a couple white stripes and then progressively more stripes, it would be more advantageous for the zebras with more white stripes in the hot sun, because they would spend less energy in trying to stay cool. It is less likely that white zebras would evolve less-advantageous black stripes over time.
But why wouldn’t the zebras just become all white? Well, there may be barriers that do not allow this, or we can just say it has happened, when we look at white horses. When we see an all-white zebra, would we call it a zebra? No, we’d probably just say it’s Shadowfax. Simply put (disregarding DNA analysis), what makes a zebra a zebra is its stripes.
In addition, the white stripes of a zebra provide camouflage. Seems like they’d really stand out against the tan backdrop of the savanna, but keep in mind that a zebra’s main predator, the lion, is colorblind. So, through the lion’s eyes, the zebra’s vertical stripes blend right in with the tall grasses. In addition, a herd of zebras may act as an optical illusion, all blending into one big clump that a predator may not want to mess with. In that way, the presence of stripes is very advantageous.
The Final Verdict
All evidence supports the hypothesis that zebras are black with white stripes. From the teratology evidence, the relation to horses, and the advantages of white stripe evolution, it would be pretty hard to argue otherwise.
So whether you see the zebra as a symbol of racial harmony or not, they are still beautiful animals. For that reason zebras are threatened by human exploitation, such as poaching for hides or capturing for captivity in zoos. To help them out, as well as the many other animals negatively affected by humans, get educated about them and how you can help to save beauty from extinction.