As the writer points out, it has long been known that ____

The fact that the brain is divided into a left and a right
half is not a new discovery. Once the skull is removed
the division is obvious to the naked eye and it is a
common feature of brains throughout the animal
kingdom. What is interesting about this division in
man is that each half seems to have developed
specialised functions, the left side appearing to be
better at some tasks and the right side better at others.
The most obvious difference in functioning is that the
left side of the brain receives sensations from and
controls the right side of the body and vice versa. The
reasons for this are still unclear. Despite a number of
interesting theories there is no obvious advantage in
such a crossover.