Language differs from call signs used by primates and other animals in that language can be used without prompting or a stimulus and is necessary for higher thinking. Call signs are regarded merely as forms of communication rather than abstract symbol use.
Although linguists have been able to allocate most languages to a small number of language "families", they have been unable to find a common origin of these language families. A few of the largest and oldest families include: [[Indo-European]], Afro-Asiatic and
Nigar Congo families (Campbell, 98).