TR: Why bats?

MC: They are identical in size to mice and have similar physiology, such as heart rate and body temperature. So we don't think there will be a level of incompatibility that would kill off the mice. But we also chose bats because we know how enormously different they are from mice. Their echolocation is almost as good as our vision. They can distinguish things on a submillimeter scale.

TR: Can this approach really shed light on something as complex as echolocation, which presumably involves a lot of genes?

MC: We certainly don't expect to make mice that can fly or echolocate. But those capabilities have individual components that we can study--the various components of the auditory system, for example.

It's also plausible that these capabilities aren't as complex as we thought. It's possible to evolve very complex things with just a few genes. There are two groups of bats: megabats and microbats. People originally thought megabats evolved from primates because their brain looks more like a primate brain, while microbats' brains look more like rodent brains. But sequencing studies show both types are related to rodents. That shows that it's possible to develop a brain that looks histologically like ours in a very short time span.

In addition, megabats have a visual system that is more similar to ours than to rodents'. We process different aspects of the visual landscape, such as color and motion, in different parts of the brain and then somehow amalgamate it into one image. Mice have a much simpler system. Megabats are fruit eaters, and so had to discern the color of ripe fruit, just like our ancestors did. The fact that this ability evolved so quickly in bats tells me that just a handful of genes are responsible.

Of course, I'm projecting projects that will take 20 years to complete. But I'm always optimistic about the research and how long I'll live! I think using your brain keeps you young, so I intend to keep using it.