The below diagram (click to enlarge) clearly shows how the bicycle has evolved over the years.
The chain of evolution was first flagged off with the invention of
push-bikes. Also known as draisines or hobby horses, these first came into
existence in Paris in 1818. Made of a wooden frame and two wheels, the draisines
had to be operated by pushing the earth with the feet while sitting on the
vehicle.
This first effort into designing a human powered vehicle, received a huge
facelift with the
introduction
of pedals and crank arms attached to the front wheel. This design was introduced
by Pierre Michaux and Pierre Lallement, two Frenchmen in the 1860s. The design
gained popularity since man could now make more efficient use of the effort he
put in moving the vehicle forward which made things more convenient. This went
on to develop into the "penny-farthing" which had huge front wheels and a high
seat. The huge front wheels ensured more distance was covered with the use of
lesser effort, but riding them was a real task due to the clumsy
weight-distribution of the vehicle.
To address these concerns, came the dwarf safeties or the safety bicycle This
one had wheels of equal diameter and the seat was placed further back. Gearing
was introduced and the pedal could now be in the centre of the bicycle. Power
was transmitted from the pedals to the rear wheel with the use of a
sprocket-chain system and the modern bicycle was born.
The safety bicycle became extremely popular and widely accepted by all people.
This resulted in a
flurry
of innovations to make the bicycle even more comfortable and rider-friendly.
John Boyd Dunlop, a Scotsman used pneumatic tires for the first time in the late
1880s and these became an instant hit and continue to be used even to this day.
Around the same time, hand operated brakes that had cables attached to
break-shoes were also invented.
By the time the 19th century was coming to an end, bicycling became a real
passion and touring on bicycles and organizing bicycle races became the norm. As
a consequence, racing bicycles and mountain bicycles came into existence.
These vehicles have stayed on for so long that getting rid of them seems to be
an impossibility. This longevity maybe attributed to continuous changes and
improvements in the way bicycles are designed and manufactured.
Continuous experiments on newer and more efficient designs are still on and
better designs are still coming out everyday.