Here's an article about how the Romans may have brought a particular gene into Britain which makes HIV easier to attack.Britons may be more vulnerable to Aids due to Roman invasion It makes one wonder how genetic makeup of cultures has changed the health makeup of the world.  Did Roman blood help people resist colds?  Did it help create larger or stronger children?  Did Celtic genes help give people any kind of advantage?  What about Viking blood?  These would be interesting issues of exploration.