FOXP2 : A master gene for language?

 

Perhaps the greatest insight into the evolution of language has come from work on the FOXP2 gene. This gene plays a key role in language and vocalization and allows us to explore the changes underpinning the evolution of complex language.
The FOXP2 gene was first discovered by Simon Fisher, Anthony Monaco and colleagues at the University of Oxford in 2001. They came across the gene through their studies of DNA samples from a family with distinctive speech and language difficulties. Around 15 members of the family, across three generations, were able to understand spoken words perfectly, but struggled to string words together in order to form a response. The pattern in which this condition was inherited, suggested that it was a dominant single-gene condition (one copy of the altered gene was enough to disrupt their overall language abilities). The researchers identified the area of the genome likely to contain the affected gene but were unable to identify the specific gene mutation within this region.
They then had a stroke of luck, in the form of another unrelated child with very similar symptoms. Looking at this child’s DNA they identified a chromosome rearrangement that sliced through a gene in the region of DNA where they suspected the mutated gene was. This gene was FOXP2.  After sequencing the FOXP2 gene in the family they found a specific mutation in the gene that was shared by all the affected family members. This confirmed the importance of FOXP2 in human language.
Simon and his colleagues went on to characterize FOXP2 as a ‘master controller’, regulating the activity of many different genes in several areas of the brain. One key role is in the growth of nerve cells and the connections they make with other nerve cells during learning and development. Mutations in the FOXP2 gene interfere with the part of the brain responsible for language development, leading to the language problems seen in this family.

The evolution of FOXP2 

The FOXP2 gene is highly conserved between species. This  means that the gene has a very similar DNA sequence in different species, suggesting it has not evolved much over time. The FOXP2 protein in the mouse only differs from the human version by three amino acids. The chimpanzee version only differs from the human version by two amino acids. These two changes in amino acids may be key steps in the evolution of language in humans.  What difference do these small changes in sequence make to the functionality of the FOXP2 protein? Studies with mice show that changing the mouse version of the FOXP2 gene to be the same sequence as the human version only has subtle effects. Remarkably, the resulting mouse pups are essentially normal but show subtle changes in the frequency of their high-pitched vocalizations. They also show distinctive changes to wiring in certain parts of their brain. From these studies scientists have concluded that FOXP2 is involved in the brain’s ability to learn sequences of movements. In humans this has translated into the complex muscle movements needed to produce the sounds for speech, whereas in other species it may have a different role, coordinating other movements.FOXP2 regulates many other genes in the body and evolution seems to have favored a subset of these as well, particularly in Europeans. FOXP2 regulated genes are important not only in brain development, but they also play important roles in human reproduction and immunity.

FOXP2 and the Neanderthals

Neanderthals have generally been characterized as a large, brutish species with little or no intellectual, social or cultural development. However, the fact that they had the same FOXP2 gene as modern humans suggests that Neanderthals may have had some capacity for speech and communication. Various strands of evidence have helped to establish a picture of how Neanderthals might have lived and communicated. Archaeological records suggest that they probably lived in small groups and due to their high energy needs, spent most of their time hunting. Neanderthals are unlikely to have developed social groups bound together by effective communication. This is probably because they lacked the key mental abilities needed to establish and maintain social groups. Recursive thinking (thinking about thinking), theory of mind (appreciating what is going on in someone else’s head) and inhibition of impulsive reactions (being able to control impulses) are all important elements to successful social interactions. Interestingly brain injury and developmental disorders, such as autism, can interfere with these abilities and social skills in humans. This evidence suggests that the Neanderthal brain may not have been wired to support effective communication and diplomatic skills. They would have been extremely difficult to get along with! The Neanderthal brain was probably better adapted to maximize their visual abilities. They would have used their oversized eyes and large brains to survive and hunt in the lower-light levels in Europe. This would limit the space available in the brain to develop the systems needed for communication and social interactions. However, their smaller social brain regions could have enabled them to establish smaller social networks which may have improved their chances of survival in the harsh European environment.