FOXP2

Why Can We Talk? 'Humanized' Mice Speak Volumes About Evolutionary Past

An article in the May 29th issue of the journal Cell reported that mice carrying a "humanized" gene showed changes in brain circuits where linked to speech and language in humans.
"A humanized version of Foxp2 affects cortico-basal ganglia circuits in mice"

This gene, FOXP2, is a transcription factor that is expressed in the brain as well as in a wide variety of other tissues.
It has been hypothesized that two amino acid substitutions (T303N, N325S) of the gene product became fixed after the human lineage split from chimpanzees, and the differences underwent selection due to effects on some aspects of speech and language.
In addition, individuals having an allele with missense mutations on FOXP2 gene suffer from a developmental impairment especially affecting speech and language.

In the study, the researchers introduced these substitutions into the Foxp2 gene in mice.
Mice having the humanized FOXP2 are generally healthy, but showed qualitatively different ultrasonic vocalizations, decreased exploratory behavior and decreased dopamine concentrations in the brain.

Furthermore, these mice had altered cortico-basal ganglia circuits and increased synaptic plasticity and dendrite length in the striatum, which have been linked to human speech.
Interestingly, mice carrying one nonfunctional Foxp2 allele showed opposite effects to the humanized FOXP2 knock-in mice.

The authors concluded that the effects on cortico-basal ganglia circuits seen in the humanized Foxp2 mice model aspects of speech and language evolution in humans.
"It will now be important to further explore the mechanistic basis of these effects and their possible relationship to phenotypic differences between humans and apes", they say.

This is an amazing report about evolution of speech and language capacity in humans. In addition, I was surprised at the number of the authors: 54 researchers.