Why do we have as many ribs as we do?

It cannot be said with certainty that exactly 12 sets of
ribs is the ideal number of ribs for all humans. Having a multiple ribs to cover and
protect the vital organs of the chest, gives a good combination of flexibility for
breathing and for movement of the torso, protection of the vial organs of the chest,
giving a rigid shape to the body and strength of the ribs themselves. Depending on size
and life style of each person we can think of instances in which 11 or 13 sets of ribs
achieving a better optimization of these requirements. However significant increase or
decrease in number of ribs - say by 50 percent - is not likely to be suitable for any
individual.

Increasing the number of ribs significantly,
making each rib thinner, will improve the flexibility of the body, but the individual
thinner ribs will become more fragile and will not be able to provide reasonably fixed
shape to the chest. The greater flexibility of the ribs will reduce the ability of ribs
to prevent outside pressure being transmitted to the organs of the chest. In addition
the increased number of ribs is likely to make the construction of the body more
complex.

Reducing the number of ribs, making each rib
thicker, will have opposite effects. That is it will make the cage covering the vital
parts of the body stronger but less flexible. Though individual rib will then be
stronger, but damage to any one rib will create more problems. With the regular movement
of the ribs for breathing, it will be very difficult for thicker rib fractures to
heal.