New research reveals that a chimpanzee’s hair color says little about its age.

In humans, gray or silver hairs usually indicate that we are getting older. And the more gray hairs we have, the older we usually are. But what about our closest relative, the chimpanzee? Scientists at George Washington University have been investigating the case. And it turns out that with chimpanzees, it’s a little different.

Photo-analysis

The reach their conclusion, the researchers collected and studied extensively pictures of multiple chimpanzees at different ages and hair color. They specifically looked at how many gray hairs the chimpanzees had. They then looked at how old each chimpanzee was at the time the photo was taken.

And so they found that the number of gray hairs didn’t tell much about the age of the chimpanzees. For example, chimpanzees with many gray hairs were not always significantly older than their peers with few gray hairs.

Different pattern

“In humans there is a fairly linear and progressive pattern,” argues researcher Elizabeth Tapanes. “You get grayer as you get older. In chimpanzees, we don’t see that pattern.” The great apes gradually become a bit grayer until the middle of their lives – how gray they get varies from chimpanzee to chimpanzee – and then their hair color changes little as they age. “Chimpanzees reach a point where their hair gets a little salt and pepper color, but they never turn completely gray, so you can’t use those hairs to estimate their age either,” the researcher explains.

Hypotheses

Why chimpanzees – unlike us humans – do not go completely gray cannot be answered by this research. But the researchers do have ideas about it, as they write in the journal PLoS ONE. For example, chimpanzees might be able to better regulate their body temperature with their relatively darkening hairs. Also, because they hardly change color, it may be easier for chimpanzees to recognize each other.

Little research

To date, surprisingly little research has been done on graying chimpanzees or other wild animals. Instead, a lot of research is being done on the physiological processes that lead to people turning gray and how we might be able to thwart those processes. However, it can be very useful to look beyond humans and look at the graying hairs from an evolutionary perspective.

At least the researchers aren’t done with the graying chimpanzees. Thus, they plan to look at the gene expression in individual hairs of the great apes. They hope to find out if there may be changes at the genetic level associated with the changes that we can see with our own eyes: namely the gray coloring of the chimpanzee’s hair.