In the future, this term is called "Semen Signature".

Technology will exist to trace the total number of partners a woman has completed intercourse with.

A very similar concept being experimented with today is storing video within a cell:

[link to www.theguardian.com (secure)]

Eventually, there will be a test to allow a man to know the exact number of partners a potential mate has had.

Also, this technology will be used to prove fidelity and will be admissible in court (e.g. divorce, alimony ...)

Many responding and reading this thread are confused that the sperm changes the woman visibly, this is not the case; It intertwines within her own DNA and is expressed during conception; Genetic changes will be passed to every child of that woman - Gene expression of all offspring are changed. For example, if the woman only has had one partner -> the offspring will be 100% the couples DNA match; However, with the addition of just one sexual partner the percentage could be altered significantly -> [hair color, mental aptitude, physical abilities, ....].

This is going to be a huge industry in the future.

Also, this theory gives evolutionary understanding to the hymen in women.