On my right side all the ribs are in line with one another. On the left side towards the bottom the ribs are all protrude about an inch less, I can tuck about a finger and a half under the rib where the difference begins.

I have heard this is quite common so I was wondering why?

Thanks

Very little about humans is truly symmetrical and the rib cage is no exception. You only have to look at faces of the people around you (or your own in the mirror) to see the vast majority of us are "lop sided" in some way. Similarly our legs and arms are not mirror images of each other and are often of different, albeit minor, lengths.

As an aside there is good evidence that the more symmetrical a person's face is the more attractive they appear to the opposite sex! Speculation on the reasons for that have centred around genetic fitness though I have to say I have always found that a rather weak argument.

Speculation on the reasons for that have centred around genetic fitness though I have to say I have always found that a rather weak argument.

To me the argument makes a fair bit of sense if you consider that a severely asymmetric face is likely to indicate some sort of serious problem. The problem could of course result from an infection or an injury, rather than from a congenital defect, but perhaps serious asymmetry was (at some stage of human prehistory) likely enough to indicate genetic abnormalities that avoiding it paid off in evolutionary terms. If this resulted in a simple instinct like "beware asymmetry!", you can see how people who are slightly asymmetric might end up being judged less attractive.