<P> Boccaccio wrote: </P> <P> How many valiant men, how many fair ladies, breakfast with their kinfolk and the same night supped with their ancestors in the next world! The condition of the people was pitiable to behold . They sickened by the thousands daily, and died unattended and without help . Many died in the open street, others dying in their houses, made it known by the stench of their rotting bodies . Consecrated churchyards did not suffice for the burial of the vast multitude of bodies, which were heaped by the hundreds in vast trenches, like goods in a ships hold and covered with a little earth . </P> <P> Although the Black Death highlighted the shortcomings of medical science in the medieval era, it also led to positive changes in the field of medicine . As described by David Herlihy in The Black Death and the Transformation of the West, more emphasis was placed on "anatomical investigations" following the Black Death . How individuals studied the human body notably changed, becoming a process that dealt more directly with the human body in varied states of sickness and health . Further, at this time, the importance of surgeons became more evident . </P> <P> A theory put forth by Stephen O'Brien says the Black Death is likely responsible, through natural selection, for the high frequency of the CCR5 - Δ32 genetic defect in people of European descent . The gene affects T cell function and provides protection against HIV, smallpox, and possibly plague, though for the last, no explanation as to how it would do that exists . This, however, is now challenged, given that the CCR5 - Δ32 gene has been found to be just as common in Bronze Age tissue samples . </P>

What was the black death and what effect did it have on europe