The paper was published Feb. 20. It suggests that there is a biological pathway underlying the observation that girls develop speech sooner than boys.
Edyta Zielinska at The Scientist has the details:
Measuring the amount of FOXP2 protein in the brain
Interestingly, they found the exact opposite in the mice they studied — higher FOXP2 levels in boys. Language is a complicated phenomenon which most likely encompasses more than one gene, the authors warn, but this is the first sex difference they've seen in gene expression.