Getting off topic here John Doe
besty, we must keep in mind that bell curves do not necessarily fit all variables, and are at best only a general guide.
Funky Derek was addressing the concept of half the people (people defined as the planet's population, everybody) being below average, average in this case defined as the arithmetic mean ( intelligence - lets use IQ - the IQ scores of n people divided by n) - half the people to the left of the centre point and half to the right ie symmetry about the mean.
It was valid of me to say that a normal distribution curve (bell shaped by definition) could be used to represent the probability density of the global population's intelligence.