Mice engineered to carry the humanized version of the FOXP2 gene show changes in brain circuits that have previously been linked to human speech, and the engineered mouse pups show qualitative differences in the ultrasonic vocalizations they use when placed outside the comfort of their mothers' nests. The FOXP2 gene has previously been putatively associated with development of speech in humans. One important difference between humans and chimpanzees are two amino acid substitutions in FOXP2. Those changes became fixed after the human lineage split from chimpanzees and earlier studies have yielded evidence that the gene underwent positive selection. That evolutionary change is thought to reflect selection for some important aspects of speech and language. "Currently, one can only speculate about the role these effects may have played during human evolution," the researchers wrote. "However, since patients that carry one nonfunctional FOXP2 allele show impairments in the timing and sequencing of orofacial movements, one possibility is that the amino acid substitutions in FOXP2 contributed to an increased fine-tuning of motor control necessary for articulation, i.e., the unique human capacity to learn and coordinate the muscle movements in lungs, larynx, tongue, and lips that are necessary for speech. We are confident that concerted studies of mice, humans, and other primates will eventually clarify if this is the case." The authors cautioned that not enough is known about mouse communication to yet read too much into what the current results might mean. The senior author of the report was Dr. Svante Paabo. The work was published in the May 29 issue of Cell.
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