If sexual selection were responsible for the giraffe's long neck, male giraffes would have evolved longer necks than their female counterparts, said the researchers, but they didn't find that to be the case.
Credit: iStockphoto
Simmons argued that studying giraffes in Zimbabwe could have skewed the results because poachers have killed most large males there.
Johan Du Toit, a large mammal ecologist at Utah State University in Logan, disagreed with Simmons and told Cosmos Online that the new study offers "solid evidence" against the sexual selection hypothesis.
Instead, he favours the feeding advantage theory, which states that long necks evolved to give the animals access to food on higher branches.
"Those individuals with higher reach will have a higher probability of surviving when food is limited," he said, "and will thus be more likely to pass on their genes to future generations."
Temperature control
Mitchell said other factors could also have played a role. For example, giraffes are much better at spotting prey at a distance than species with their eyes closer to the ground. Furthermore, the long neck may be helpful for keeping the animals cool, by increasing relative surface area for heat loss.
"We think that temperature control, vigilance and feeding are all major benefits of having a long neck," he said.
Research into the origin of the giraffe's long neck could help scientists answer some more general questions too. For example, studying the development of vertebrae in the neck could provide important insight into what controls the length of bones in other animals, including humans.
"In general, the principle is that species that have extraordinary adaptations are the ones that will give the most insight into how things work [in all animals]," Mitchell said.
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