The first human slang could have been a rudimentary system of visual, tactile and auditive calls, resembling animal communication. But when we acquired the ability of representing objects through symbols and communicate to another individual our own mental creations, we turned ourselves different from the rest of the living things. Speech had 'emerged'.

The skill of articulating words with meaning fascinated the philosophers of all epochs. Plato was asking about the relation between the words and the things they designed. The creationist theories solved this attributing to a divine being the genesis of the language. But after Darwinism, paleontologists and linguists looked for the "missing link", the prodigious factor that opened the door towards words.

The most common question is: is speech born or acquired? When did we get the skill? Which are the factors of the natural selection that contributed to this? Did its emergence boost the development of our intelligence or did our intelligence determine the emergence of the speech? How could the brain have organized the structures that allowed the speech?

We clearly know that the first symbolic language emerged 2.5 million years ago, when Homo habilis started to fabricate the first stone tools. This ability surely played a key role in the development of symbolic communication. Instead, articulating went perfecting till Homo sapiens, who was already emitting sounds similar to that spoken by modern humans.

The mouth, nose and larynx ended by transforming themselves into a refined apparatus, in which the air was converted into vowels and consonants due to a better position of the tongue and lips. Moreover, the acquisition of a grammar and syntax was the result of an evolutionary process, while the writing ability was the consequence of the phonetic interpretation of the primitive icons.

Bipedalism (walking on two feet) released the hands from the locomotory function; the use of the free hands led to the development of the brain and of the speech. In fact, all the functions necessary for controlling the language (articulating control, data storing and integration of the grammar rules) have their centers in the left hemisphere, the same that controls the movements of the right hand and 99 % of the humans are right-handed.

That's why some researchers consider the two skills (speech and hand use)are connected to bipedalism. Others think that the use of the right hand was anterior to the speech and this fixed in the same hemisphere because at the beginning humans communicated with their hands.