How do the world's only flying mammals communicate? Researchers have observed young bats adopting new “dialects” simply by hearing them repeatedly, making them one of the few animals known to have a capacity for vocal (声音的) learning. “These bats may help us clarify the evolution of speech acquisition (习得) skills,” says Yosef Prat, a PhD at Tel Aviv University (TAU).
For one year, researchers raised 14 Egyptian fruit bat pups with their mothers in controlled area, exposing each young bat to two different vocalizations: the natural call of its mother and a separate recording that varied in pitch (音高) or frequency. They found that the pups in each group developed a dialect like the recording. “The general assumption in this field is that most animals develop their born vocalizations regardless of what they hear, and that human vocal learning abilities have developed during evolution,” says Mr Prat. “The finding that bats learn the common dialect in their rest place was unusual.”
Scientists know little about the origin of spoken language, which is believed to have appeared in humans within the past 500,000 years. Dozens of theories attempt to explain the complexity of this skill, but none have done so conclusively.
“Studying vocal communication and vocal learning in animal models is a very useful way to approach the problem,” says Olga Feher, an assistant professor at the University of Warwick in England.
But animal vocalizations and human speech are very different things, says Jamin Pelkey, a professor at Ryerson University. “All species communicate. Unlike other animals, though, human beings are able to use sound patterns for functions that are far stranger—functions that are imaginative, theoretical, and critical. When speech is involved in these stranger functions, that is what we mean by spoken ‘language'.”
