The results of decades of breeding practices cannot be quickly undone. In the past, viral infections and mites have devastated genetically diverse honeybee populations. The genetic diversity of the honeybee population continues to decline. Lack of genetic diversity can make honeybees more vulnerable to adverse conditions.
The current sharp decline in commercial honeybee populations has been attributed to the same viral and bacterial infections, pesticide poisonings, and mite infestations that devastated bees in the past. Whichever of these adverse conditions is the immediate cause, it is highly likely that there is also a long-ignored underlying condition, and that is inbreeding. Decades of breeding practices meant to maximize pollinating efficiency have limited honeybees' genetic diversity.
Which one of the following is an assumption that is required by the argument?