Intelligence allows humans to manage their surroundings, experience feelings, control their actions and store memories. However, what truly defines a human in this respect is the capacity for symbolic thought. It is this ability that has spawned the many creations and inventions over human history.
While animals communicate using vocalizations, complex language is something exclusive to humans. Scientists are not entirely sure when language came into existence, but they theorize that it developed gradually from roots called proto-language. It is likely that language began with simple gestures, developed into single words and eventually turned into a system of complex sentences.
No other living thing on Earth is capable of creating elaborate paintings and images, which started as far back as 35,000 years ago. Cave paintings of animals and other symbols have been found in Europe. Jewelry estimated to be 40,000 years was made from shells and beads. Music is another human trademark. The oldest known instrument is a 30,000-year-old bone flute.
While tools such as hammers and chainsaws are taken for granted in modern society, such devices had humble, primitive beginnings. Some animals, such as chimpanzees, use certain objects as tools, but they are not nearly as complex as what humans can create. More than 2 million years ago, Homo habilis, the predecessor of Homo sapiens, learned to make cutting tools through a painstaking process of trial and error. One million years later, the hand ax was invented. About 300,000 years ago, Homo erectus was able to perfect stone-cutting, which led to the development of more complex tools. Once humans started settling, the need for containers emerged. As a result, pottery came into play 12,000 years ago.