It turns out that a type of cell found in the human central nervous system that had previously been thought little more than a sort of "housekeeper" cell is actually really important for cognitive function. How did we learn this? A team of researchers used them to create mouse-human hybrids.

The cells are a type of glial cell -- neuronal support cells -- called astrocytes. These are star-shaped cells found in the spinal cord and brain -- and the most abundant cells found in the brain. They provide biochemical support for the cells that make up the blood-brain barrier, nutrients to the nervous tissue, regulation for the transmission of electrical impulses in the brain, even structural support. They're busy little guys; and, in humans, they're larger, more abundant, more diverse and more complex than in other species.

And, apparently, their role goes far beyond support.

"This study indicates that glia are not only essential to neural transmission, but it also suggests that the development of human cognition may reflect the evolution of human-specific glial form and function," University of Rochester Medical Center neurologist Steven Goldman said of a study published last year.