An analogy used when fax machines were common to describe a process that gives diminishing returns. When a document is sent between fax machines, the resulting copy is not
perfect. If this copy is itself sent to a fax
machine, the resulting copy of that copy is
even further from the original, and so ad infinitum.
Cloning for countless generations has rendered these people
impotent and hideous, their genetic structure degraded to the
point of near inoperability. The effect on their DNA from the creation of each new generation of clones was, in
essence, like faxing a fax.