True, the medieval Black Plague did kill off a third of the population of Europe in wave after wave of pestilence.
But a new study has found that the population that survived lived longer that before the plague. It somehow increased human life span.
There are reason this might be. One is that the plague struck the frail more severely than the healthy. It cretaed a stronger population.
The other is that, with a good chunck of the population gone, there was more resources for those left. Post-plague, they had a healthier diet.
To read the full article, go to http://www.huffingtonpost.com/2014/05/11/black-death-europeans-pandemic_n_5289650.html?utm_hp_ref=science