t has been estimated that over 6,000 languages are spoken around our world. The most significant characteristic that sets human tribes apart from other animals is probably the ability of speaking. We express our language through various ways. The most common one is speaking. Our brains transform our ideas into sentences. Our vocal apparatus then pronounce them out word by word. Then the question is how come only human owns the ability of speaking? Chimps are our nearest relative. However, they don’t talk, but we do. Why only human has developed this intelligent skill during evolution?
The history of studying the development of human speech can be traced back to 1990. In a British family known as “KE”, about half the family members have severe difficulties in speaking over three generations. It is a diffuse condition that includes not only the impairment in linguistic skills, but also broader intellectual problems. By looking at their inheritance pattern, an inactive FOXP2 copy was found and this can be associated with this complicated condition. FOXP2 also appears in other animals, including chimps. The difference is that during the transcription of human FOXP2, two amino acid substitutions are mutated. This inherited mutation of FOXP2 has played an essential role during the development of human speech.
An experiment is conducted recently by German neuroscientist Christiane and her team. Two specific amino acids, which are proposed to be responsible for human speech development were collected from human and introduced into the corresponding gene of mice. These mice’s behavior were observed and compared to the other mice’s which are with the mouse version of FOXP2 later.
As the scientist has proposed, human version of FOX2 dose has strong impact on the development of language ability. Mice that have human version of FOXP2 can learn more quickly than normal mice. Christiane designed a maze for mice to solve. Visual clues are labeled on the maze’s surface to show the right direction to turn. A water resource is designed to be the reward of the maze. Both groups of “humanized” mice and normal mice are involved in this test. After a continually practice for eight days, “humanized”mice are able to follow labeled clues and find the water resource 70% of the time. It spends normal mice another four days to achieve the same level. The test approved that human FOXP2 does have effect on the ability of integrating information and learning.
Another significant outcome of this experiment is that mice with human version FOXP2 can produce altered ultrasonic squeaks, while the normal mice cannot. This fact approved that mutated FOXP2 can help species learn the complex muscle movements and performing different form of sounds.
Speaking is the expression of our mind and our minds are based on human cognition. Thought the development of language cannot only rely on the single mutation of FOXP2, this new discovery takes us a big step forward on the journey of the finding the evolutionary roots of human speech.
Shuyun Sarah Wang
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