In the 19th century, the legendary English naturalist Charles Darwin introduced humanity to the theory of survival of the fittest. Through this theory, he explained, among other things, why giraffes have long necks. Millions of years ago, giraffes with longer necks could reach more leaves from tall trees compared to other animals, allowing them to thrive in competitive environments. Ultimately, this physical trait became ingrained in giraffe genetics.
Recently, scientists in the United States built upon Darwin’s discovery and proposed a new theory. According to their research, this evolutionary trait initially developed in female giraffes. Biologists from Pennsylvania State University noted that female giraffes have proportionally longer necks than their male counterparts. This is likely due to the heightened nutritional needs of females during pregnancy and while nursing their young. To conduct their study, a team led by Professor Douglas Cavener gathered thousands of photographs of these animals, including both captive giraffes and wild Masai (or Kilimanjaro) giraffes of the species Giraffa tippelskirchi, which is found in East Africa.
What did the researchers discover? Professor Cavener explained that giraffes are extremely selective eaters, consuming leaves from only a few types of trees. Their longer necks allow them to delve into dense foliage and reach high branches to access the best leaves that no other animals can reach. “When females reach four to five years of age, they are almost always pregnant and nursing,” the professor noted. Thus, his team believes that the increasing nutritional demands of female giraffes led to the “evolution of long necks.” Due to their higher need for nutrients, females require longer necks, the scientists observed.
They found that both captive and wild female giraffes have proportionally longer necks than males. Females also have proportionally longer bodies (the part of the body excluding the legs, neck, and head), as reported by the Daily Mail. But what about the males? Meanwhile, adult males have longer front legs, which make it easier for them to position themselves with females during mating. Males also have wider necks, which help them withstand blows from rivals during fights for mates. The researchers proposed a hypothesis they dubbed “necks for sex.” According to this theory, males with longer and thicker necks are more successful in defeating their competitors, finding mates more quickly, reproducing, and passing on their desirable genes to their offspring.
Experts believe that males typically grow more rapidly during their first year of life. However, their body proportions change significantly after they begin exploring their sexuality around the age of three. In the report dedicated to the study, the team wrote: “The initial evolution of the giraffe’s long neck and legs was driven by interspecies competition and the nutritional needs of mothers during pregnancy and lactation. Subsequently, the mass of the neck increased even more significantly due to competition among males and sexual selection.” The results of the study were published in the journal Mammalian Biology.