 Speculation about the origins of human language is as old as history. Although there is disagreement about the exact time, language, as we know it today, probably appeared relatively late in the prehistory of humans. We will look at two central aspects of language evolution in this e-lecture. First, we will discuss the biological prerequisites for human language, and then we will speculate a little bit and discuss the main hypotheses about the origin of human language. Let us start with the biological prerequisites. The evolution of human language is closely connected with changes in two organs essential for the use of language. The structure and the size of the human brain and the shape of the vocal tract. Anthropologists have collected evidence that from about two million years before Christ onwards, Homo habilis and Homo erectus had developed a brain fit for basic linguistic tasks. And they discovered that with the advent of Homo sapiens at around 400,000 years before Christ, from Archaicus via Neanderthalensis to Homo sapiens himself, that Homo sapiens developed a vocal tract that gradually became ready for the use of some sort of speech. Let us look at these two prerequisites in more detail. The most important prerequisite for the production of language is a well-developed central nervous system with an elaborate cortex. While the Australopithecus cortex volume did not exceed 600 cubic centimeters, Homo sapiens exhibits an average brain volume of roughly 1,400 cubic centimeters. Here are the approximate figures. Now Australopithecus brain, as we heard, has a volume of roughly 500 cubic centimeters. Habilis brain is larger, roughly 750 cubic centimeters. Homo erectus had a brain whose size was something like 900 cubic centimeters and Archaicus, the first representative of Homo sapiens, increased this once more to 1,200 cubic centimeters. And Homo neanderthalensis brain was even larger with 1,500 cubic centimeters. However, brain size alone is not the key factor. The brain of Homo neanderthalensis was even larger than ours. Yet, well, you all might know what happened. Thus we shouldn't solely examine the size, but rather the structure of the brain. And here it is known that three brain centers are primarily responsible for the production and comprehension of speech. The first of these centers is referred to as Broca's area. It can be found in the front of the left hemisphere of the cortex. And it was named after the French physiologist Paul Broca who lived in the 19th century. It is commonly known as the motor center for speech. According to recent insights, Broca's area is not a unit. Rather it is responsible for several aspects such as word associations, ordering principles, speech output, to name a few. The second brain center is referred to as Wernicke's area. Named after the German physiologist Karl Wernicke, it is commonly known as the sensory center for speech that is primarily for the reception of speech. Last but not least we have the gyros angularis which is a kind of switchboard for all sorts of neural impulse. For example, it establishes neural associations between the shape and the sound of objects. The investigation of hominid skulls has shown that as early as Homo habilis, who was around from 2.3 million years before Christ onwards, all these centers were relatively well developed. Thus the brain of Homo habilis was ready for the cognitive foundations of some sort of language. The second prerequisite is a particularly shaped vocal tract and this vocal tract must be in a position to produce a sufficiently large sound repertoire. This involves, apart from the lips that are involved in rounded versus unrounded vowels such as u versus e, a special source of phonation. That is, we need the larynx with the vocal folds and also we need a flexible resonance chamber that can amplify and modify the fundamental frequency created by the sound source in the larynx. Interestingly, the larynx and the size and shape of the oral cavity are closely connected. Let's look at this connection in more detail. Now here you see the vocal tract on the left-hand side and two views of the larynx, the anterior view and the side view. Now on top of the larynx we have a very interesting bone here in the two views, referred to as the hyoid bone. This horseshoe shaped hyoid bone is linked to the tongue by means of a particular connection referred to as the hyoglossus. Let's illustrate this by moving this sort of larynx into the vocal tract. Now this would be roughly the larynx position and here is the connection between the tongue and the larynx, the hyoid bone, the so-called hyoglossus. The interesting effect is the following. A lower larynx position leads to a retraction of the tongue and this is exactly what happened during evolution. The larynx of early representatives of Homo was relatively high, enabling him to breathe and eat simultaneously. The sound production capabilities however were restricted. During evolution probably due to the increasingly erect position the human larynx descended into the throat leading to a separation of uvella and epiglottis. This in turn has the consequence that the human vocal tract is now subdivided into two chambers responsible for the essential formant frequencies. Now the lower larynx position has led to these two resonance chambers. And now with this lower larynx position and a vocal tract which is clearly subdivided into an oral cavity and into a pharyngeal cavity Homo sapiens can produce a wide range of speech sounds. Now with the advent of Homo sapiens at around 400,000 years before Christ the vocal tract gradually became ready for the use of some sort of speech with a relatively large sound repertoire. But why did language emerge? Well, this leads us to the discussion of hypotheses of language origin that the predecessors of Homo sapiens were capable of using some sort of communication system is undisputed. How then could we explain the constant growth of the brain from Homo habilis to Homo sapiens? However, the initial impetus for the use of language is unclear. Ignoring these theological claims of language origin represented by these pictures there are several modern hypotheses about the emergence of language. One of them is referred to as the gestural hypothesis. Even though there are no apes in the ancestral line of Homo sapiens the discovery that apes can learn to communicate by means of gestures constitutes the basis of the gestural hypothesis of language origin. This scenario is obvious. Once Homo stood erect he had his hands free for complex social interactions. The problem is explaining how and why and when gestures gave way to vocal signals of communication. One proposal is that tongue movements accompanied hand gestures. Whenever we have to perform complex tasks our tongue supports our hands. For example, if young children write their tongue often goes like this or if you have to thread something through a needle's eye you go is this evidence for relationship between tongue flexibility and language emergence we may speculate. The vocalization hypothesis suggests that language evolved from a relatively small set of instinctively used discrete calls shared by all hominids. They could have sounded like that. Well, whether it was really like that you may speculate again. But such a hypothesis might explain why all languages of the world are still so much alike in terms of their sound repertoire. However, before any significant precursor to real language came into being our ancestors had to become capable perhaps by means of sudden genetic mutation of combining vocal signs in sequences having indefinitely different meanings. And thereafter our ancestors who had shared millions of years of common evolutionary changes rapidly dispersed over our planet beginning racial and linguistic diversification. The neural hypothesis holds that language resulted from a gradual increase in general intelligence documented by an increase in brain volume as we saw earlier on and thus an increase in the precision of the wiring of the neural network. An interesting hypothesis of how modern language could have emerged is referred to as the mother-child interaction hypothesis. Language could have evolved through time as a consequence of the interaction between the immature newborn baby and its mother. The newborn infant, unlike any other mammal is highly immature and has to be looked after all the time. When hominids started walking on two legs it became more and more difficult for them to look after their babies. Increasing mobility required that adults primarily the mothers had to take their babies with them. At first this was relatively easy. The baby simply holding on to the mother's fur. However, with a gradual loss of fur and nothing to hold on to the young ones had to be carried preferably on their left arm as this picture here illustrates. It may be that during those many occasions when it was being carried the baby first used vegetative sounds like burping, crying, then comfort cries and eventually some sort of babbling like mum, mum, mum, mum, mum and its mother reacted. Such phases can today be observed during the early periods of language acquisition. Well, let's summarize. The development of language was not a matter of sudden changes but rather a continuous development over millions of years. The phases of this development can still be seen in many features of modern language behavior. Gestures, facial expressions, primitive crying and shouting, babbling and intonation are steps towards real language. Initial traces of language could thus have appeared as early as Australopithecus or even earlier. Homo habilis and Homo erectus were even more likely to have used language already. They left behind stone tools that suggest some degree of acquired technology. Some sort of language can be assumed to have contributed to this level of technical sophistication. Homo sapiens appeared at around 400,000 years before Christ and it is extremely difficult to believe that he lacked language. His brain was certainly large and complex enough and his vocal tract was ready for speech.