Boys and their cars

What is it that makes boys love cars at such an early age?  It is their favorite toy that they will sit with for awhile.  The Girlchick would sit and play for extended periods at a time, but not with cars.  The boys will not play with many toys for extended periods, but the cars are by far the most favored.  Why is that?  I must ask my friend, the sociology professor.  There isn't a lot at this point that will hold their interest for this long.  They grow bored with most things - even new toys - pretty quickly.  I have to say that this was the best present ever!  Thanks for that Eichs family.