The Neandertal FOXP2 showed the same two mutations that the human gene carries (compared with the chimp version). The group did not find any genetic evidence of interbreeding between humans and Neandertals, leading them to conclude this incarnation of the gene must have propagated and spread prior to the genetic split of the two hominid species more than 300,000 years ago. Simon Fisher, a molecular neuroscientist at the University of Oxford in England, says the new work shows a better method for dating the evolution of certain genes, as opposed to inferring from changes throughout human evolution. He was more cautious about its link to Neandertal's speaking ability. "We do not think of FOXP2 as 'the speech gene,'" he says. "It is instead just one piece of a complicated puzzle, which likely involves many different factors. … The FOXP2 gene has been around for a very long time, found in similar form in distantly related vertebrate species, and it may be important not only for brain development and function but also in other tissues."
Association studies between FOXP2 polymorphisms and susceptibility to different pathologies of language impairment, such as specific language impairment, dyslexia or autism have not produced robust results, but the identification of two coding mutations related to verbal dyspraxia. Nevertheless there are strong evidence of the importance of the gene in development and some aspects of language including the fact that CNTNAP2, a downstream target of FOXP2 has been related also to language disorders. In schizophrenia, preliminary association studies have delivered controversial results... We hypothesized that FOXP2 could be considered a candidate gene that may confer vulnerability to schizophrenia or to the language related symptoms of this disorder.
FOXP2 switches other genes on and off. Geschwind's lab [at the Institute of Psychiatry at King's College London] scoured the genome to determine which genes are targeted by human FOXP2. The team used a combination of human cells, human tissue and post-mortem brain tissue from chimps that died of natural causes... The scientists focused on gene expression -- the process by which a gene's DNA sequence is converted into cellular proteins. To their surprise, the researchers discovered that the human and chimp forms of FOXP2 produce different effects on gene targets in the human cell lines.
FOXP2 cannot be called 'the gene for speech' or 'the gene for language'. It is just one element of coplex pathway involving multiple genes, and it is too early to tell whether its role within that pathway is special.
The FOXP2 gene belongs to a group of genes that make proteins containing forkhead-box (FOX) domains. FOX proteins are themselves just one subtype of a much larger group, known as transcription factors, which are involved in controlling the genetic programs of cells.
Other animals possess their own versions of FOXP2, suggesting that it might be possible to determine which evolutionary changes to the gene’s DNA sequence are most closely related to our ability to talk. This year molecular biologist Wolfgang Enard of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, explored that possibility with an extraordinary experiment: He inserted the human version of FOXP2 into mice and studied the effects on the creatures’ brains and vocalizations. Enard and his collaborators found that neurons in the brains of mice with human FOXP2 showed greater plasticity, the ability to change the strength of their connections with one another. Such plasticity might be involved in vocal learning, he suspects.
The effects of this gene on learning processes are consistent with previous demonstrations that it regulates the expression of target genes involved in neurite outgrowth and synaptic plasticity. This work opens up a new perspective for understanding how disruptions of FOXP2 lead to disordered speech and language development. In humans such mutations may affect not only the sequencing of articulatory gestures necessary for fluent speech, but also the ability to associate auditory percepts with the corresponding motor programs for vocal imitation as found in a songbird model. The phenotypic differences we observed between the mutation types in mouse models suggest the existence of, so far undescribed, differences in learning performance in humans with distinct FOXP2 mutations.
The gene Foxp2 of the forkhead gene family is expressed during the ontogeny of the mammalian brain in areas such as the deep layers of the cortex, medium spiny neurons of the basal ganglia, parts of the thalamus, and the Purkinje cells of the cerebellum. Foxp2-expressing neurons in these structures belong to distributed circuits involved in motor coordination, procedural learning and acquisition of motor skills, and sensory-motor integration and learning. Such brain circuits are also of crucial importance for learning the complex orofacial and laryngeal movements for speech production and for reaching language competence.
Last year another group of scientists compared the the human version of FOXP2 to the sequence in our close primate relatives. They found that chimpanzees have a version of the gene that’s hardly different from the gene in mice. But in our own lineage, FOXP2 underwent some fierce natural selection. By comparing the minor differences in FOXP2 carried by different people, the scientists were able to estimate when that natural selection took place–roughly 100,000 years ago. That’s about the time when archaeological evidence suggests that humans began using language.
FOXP2 belongs to a family of genes found in animals and fungi. They all produce proteins that regulate other genes, giving them a powerful role in the development of the body. FOXP2 in particular exists in other mammals, in slightly different forms. In mice, for example, the part of the gene that actually encodes a protein is 93.5% identical to human FOXP2. And studies on mice show that it plays a crucial role in the developing mouse brain.
An English family known as “KE” revealed the link between FOXP2 and language. Many members of this family have severe difficulties with language. They struggle to control their facial movements and have difficulty with reading, writing, grammar and understanding others. In 2001 Fisher [an Oxford University researcher] and his colleagues found that the gene at the root of the family’s trouble is FOXP2, located on chromosome 7. The gene makes a protein that binds to DNA, switching other genes on or off.
“Nothing shows that Neandertals didn’t have language abilities,” says Johannes Krause of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. Indeed, the recent finding by Krause and his colleagues that Neandertals and humans have the same version of the gene FOXP2—the only gene linked to language so far—might be thought of as evidence that they did. But although studies of modern humans suggest that FOXP2 is necessary for speech, no one believes that it is sufficient.