By Carrie Williford | November 19, 2021
According to fossil records, giraffe ancestors’ necks began to grow longer around twelve million years ago. more rest and they have the adults to look out for them while they are asleep. And, since they’re smaller, it’s easier to get up and down. 1 Why this happened isn’t completely clear.
Beginning with Charles Darwin, the most common assumption is that the giraffes with longer necks could reach higher branches, eat more of the food, and thrive better than those with shorter necks. 2
A 2007 study did show that giraffes can feed at any level but when there is competition for food by other (shorter) herbivores, their necks allow them to eat the food far above where their competition feeds. A giraffe’s neck is indeed an advantageous feature when it comes to eating. 3
A competing theory is that a giraffe’s neck contributes to sexual selection. Male giraffes fight with each other frequently. They swing their necks at each other and whomever wins is considered the dominant giraffe.
The sexual selection theory states that females prefer to mate with taller males with stronger necks. So, if the giraffes with the longer, stronger necks are the ones fathering the babies, that will create a taller giraffe over time. more rest and they have the adults to look out for them while they are asleep. And, since they’re smaller, it’s easier to get up and down. 1
What about female giraffes? Their necks grew as they continued to mate with the longer necked males. 2
This theory appeared in a paper from 1996, and there have been plenty of rebuttals to it. One argument states that there are not enough differences between males and females to put so much emphasis on the males’ necks as to why the species as a whole looks the way it does. Additionally, a study showed that males with larger, stronger necks are not always the ones winning the fights! 4
An argument against both of these theories is that they are based on living giraffe’s behavior. We don’t know the reason giraffes’ ancestors may have developed longer necks. It could be reasons that aren’t even applicable anymore (ecological change, for example) and that the reason their necks evolved back then have nothing to do with the ways giraffes use them now.
- Anne Innis Dagg, 5 Giraffes: (Markham, Ontario: Fitzhenry & Whiteside, 2016)
- Brian Switek, “Why do giraffes have long necks? The mystery has baffled experts since Darwin,” Wired, June 21, 2017
- Elissa Z. Cameron1 and Johan T. du Toit1, “Winning by a Neck: Tall Giraffes Avoid Competing with Shorter Browsers,” The American Naturalist 169, no. 1 (January 2007)
- Riley Black, “Giraffe Necks Not for Sex,” National Geographic, January 15, 2013.