Humans are polyclonal beings since each one of us is born of

a unique fertilization event. Rarely, however, two babies can 

develop from a single embryo producing monoclonal babies.

Referred to as monozygotic (MZ), identical twins are true
reproductive clones; like Dolly they share a genome but 

breathe a sovereign existence. 

Taking place every 50 seconds worldwide, MZ twinning

is more prevalent than any genetic disease yet its cause
has remained enigmatic.