Why do giraffes have long necks? Scientists reveal fascinating new theory

Charles Darwin famously used his “survival of the fittest” theory in the 19th century to explain why giraffes have long necks.

Millions of years ago, giraffes with longer necks could reach more leaves on trees and survive competition, before passing the long-neck trait on to their genes, the legendary English naturalist said.

Now, scientists in the United States elaborate on Darwin’s findings with a new theory, and believe that it was women who drove the evolutionary trait.

They found that female giraffes have proportionally longer necks than males, and the cause was likely the high nutritional needs of females during pregnancy and lactation.

Interestingly, female giraffes have a more sloping body shape, while males are more upright, which may help develop their love interest.

The study, which builds on Darwin’s theory rather than disproving it, was led by Douglas Cavener, a professor of biology at Pennsylvania State University.

“Giraffes are picky eaters,” Professor Cavener said.

“They only eat the leaves of a few species of trees, and their longer necks allow them to penetrate deeper into the trees to obtain leaves that no one else can get.

‘Once females reach four or five years of age, they are almost always pregnant and nursing.

“Therefore, we believe that increased nutritional demands on females drove the evolution of giraffes’ long necks.”

Due to their higher nutritional demand, females need a long neck to reach deep into the trees and obtain the best leaves, Professor Cavener and his colleagues say.

For the study, researchers gathered thousands of photographs of captive and wild Masai giraffes (Giraffa tippelskirchi), a species native to East Africa.

They found that in both captive and wild adult giraffes, females have proportionally longer necks than males, relative to the overall height of the animal.

Females also have proportionally longer “trunks” (the main section of their body that does not include the legs or neck or head).

Adult males, on the other hand, have longer front legs (effective for mounting the female during mating) and wider necks (which can take hits from rival males during fights).

According to experts, males generally grow fastest during the first year and body proportions do not differ significantly until they begin to reach sexual maturity around three years of age.

A more recent hypothesis called “necks by sex” suggests that the evolution of long necks was driven by competition between males, who swing their necks at each other to assert dominance, called neck combat.

‘Necks by sex’ suggests that males with longer, thicker necks have been more successful in competition, leading them to reproduce and pass their genes on to offspring.

“The sex-neck hypothesis predicted that males would have longer necks than females,” Professor Cavener said.

“And technically they have longer necks, but in males everything is longer: they are 30 to 40 percent larger than females.”

The team doesn’t reject the sex-collar hypothesis, but if it had any effect, it probably came later.

They write in their study: “The initial evolution of the giraffe’s long neck and legs was driven by interspecific competition and the maternal nutritional demands of gestation and lactation through natural selection to gain a competitive advantage.

“Later, neck mass increased further as a consequence of male-to-male competition and sexual selection.”

The new study has been published in the journal mammal biology.