![]() Gestures are movements of the hands, arms, or body that are used to communicate. We think that the ancestor of humans, chimpanzees, and bonobos probably used gestures to learn language. But we think that other animals, especially those that are closer to us on the Tree of Life, can learn simple language if they grow up in a home where others use language, and expect them to use language, like human children do. People use language to tell other people about things (for example, “The sky is blue.” Or “The fire needs more wood.”) People usually do not tell their dog such things because dogs communicate, but they do not use language like humans do. For example, many people have dogs and they know that a dog can learn to follow many commands. Some people think humans are the only animals who can learn language. Instead, that one species probably developed the skill after growing apart from the other species in that branch. If only one species in a branch can learn a skill, the shared ancestor probably was not able to learn that skill. If all of the species in a branch of the tree of life can learn a skill, they probably inherited that skill from their shared ancestor. We can study the behavior of animals that are alive now in order to learn about the likely behavior of their ancestors. Chimpanzees and bonobos have also changed over millions of years, but in their own ways. Bonobos and chimpanzees continued to become what they now are even after humans branched off from them. Humans became a different species from bonobos and chimpanzees 5–7 million years ago. The three species–humans, chimpanzees, and bonobos–share an ancestor. Humans are more like chimpanzees and bonobos than they are like the other apes, so they are closer on the Tree of Life. Humans and the other apes share an ancestor, which means that if you follow the branches of the generations of parents of humans and other apes back far enough, you come to the same animal (our shared ancestor). Beings on the higher branches came into being after beings on the lower branches, who are their ancestors. Species that are similar to each other, such as reptiles, dinosaurs and birds, or other apes and humans, are close together on the Tree of Life. Each branch of the Tree of Life represents a species. The Tree of Life is a map of the types of animals and other living beings in the world. The process by which a species changes over time and a new species comes into being is called evolution. Creatures on the higher branches came into being after creatures on the lower branches, who are their ancestors (see Figure 1). Species that are similar to each other, such as dogs and wolves, deer and elk, sun fish, cat fish and gold fish, polar bears and grizzly bears, are close together on the Tree of Life. The Tree of Life has so many branches on it that it looks like a tree. It is a map of the types of animals and other living beings in the world. The other apes are closely related to people on what biologists call the Tree of Life. Animals from the same species can make babies together. ![]() Humans, chimpanzees, bonobos, gorillas, orangutans, and gibbons are all apes. Apes are like monkeys, but larger and without tails. Luckily, baby apes hold clues about the history of language. The question of how languages came into being is hard to study, because old languages do not leave skeletons behind. Our study also shows that putting sounds and gestures together was an important skill that early humans could build on to create language over thousands of years. Our study shows that the ancestor of humans, chimpanzees and bonobos probably used gestures to communicate. The child used her voice while gesturing more than the apes did. They used gestures when they were young and later added symbols. The chimpanzee, bonobo, and human child used many of the same gestures. The apes’ symbols were pictures called lexigrams the child’s symbols were spoken words. A symbol can be visual or spoken the important thing is that it means something. Did language grow from gestures? That is, was using the hands, arms, or head to communicate a step toward the development of language? We studied gestures and symbols used by a chimpanzee, a bonobo, and a human child who were all taught to use symbols.
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