Abstract
Speech enables humans to communicate effectively and is probably the most prominent trait which distinguishes people from other creatures. However, some people are born with an impaired ability for language and speech development, a syndrome known as specific language impairment (SLI). Children with SLI lag behind their peers in language development and comprehension, which contributes to learning and reading disabilities in school. Recently a defective gene in a three-generation family that had the SLI speech disorder was identified as the FOXP2 gene. The FOXP2 gene was also defective in a non-relative who suffered from the same disorder. Those with a defective FOXP2 are more prone to display SLI difficulties, but the same mutational variants do not always result in this disorder, reflecting the complexity of the genetics of speech.