Human life span has increased or decreased?

I think overall it's increased.

it has decreased

Yes it has as a whole world, even in country that have a shorter life span than some of the world leading ones. However I believe with the amasing medical improvmets that have come about it helps all unfortunatly there is big bussiness greed and Bottom line that lets the countrys/ people with money a better chance of better quality of life. some does get the the third world countrys by small groups where you are born and to whom really puts one at a advantage or disvange,, not really right I believe one must put something back into their community ( all can do if makes the effort in some orginazation )

as per the scintific data, it has decreased significantly

with the kind of advancement in medical research we have witnessed..human life span has increased..but because of the kind of lifestyle most people lead...it kinda balances out..so there's a check on the population problem too

It has decresed like anything

Well of course it's depend on area. For example life span in average has gone up in England (and America) where as Iraq it's shot down dramatically.