why wy?

Another interesting link explaining why human babies take so long to walk.

Here's an except:

If babies’ heads got any bigger, they would get stuck in the birth canal and kill both mother and child. Although natural selection worked to maximize what could be done—for instance, babies’ heads compress as they twist their way around the bones in the pelvis—there simply is not enough room for a big, mature brain to pass through.

As it turned out, the evolutionary answer was to let the brain keep growing outside the womb before it matures. So in contrast to other mammals, humans have a good bit of development to do after birth.