Education in terms of medical 'break throughs' that have allowed us to combat diseases that would normally wipe out large segments of humanity. An example being the fast responce by the WHO (World Health Organization) when the Ebola virus first came to light in (I believe it was) Kikwik (sp), Africa. If this disease had made its way into a populated city or futher we might now be only two thirds of the population we are presently at. Diseases like this or similar in their killing potential used to decimate different populations of the world in the past (i.e. the "Black Death" in Europe which wiped out anywhere from one third to half the populous). Now, because of technology, we seem (at least at present) to have been better equipped to deal with such things so that they haven't decimated the world's populous. This goes equally for fighting the spread of 'hoof and mouth' disease in cattle. Things that in the past could have caused great depopulation in the areas that were affected.
Things that used to significantly reduce our populations have decreased due to education and the ability though our machines to combat their effects on societies. This is not to say that something in the future could not simply overwhelm us (which I believe is quite possible) but to say that these are some of the factors which have allowed our World population to increase to its present day size.
There are other factors as well but I think you can see my point.