The Pennsylvania Bill of Rights (1776) begins with the following (emphasis added):

That all men are born equally free and independent, and have certain natural, inherent and inalienable rights, amongst which are, the enjoying and defending life and liberty, acquiring, possessing and protecting property, and pursuing and obtaining happiness and safety.

Many other state constitutions echo this "defending life" language, and some state courts plausibly read it as securing a constitutionally protected right of self-defense. (We can set aside for now the debate about the right to bear arms in self-defense; for now I'm interested in the rhetoric about self-defense more generally.) Interestingly, this is a departure from the Virginia Declaration of Rights (1776), which says,

That all men are by nature equally free and independent, and have certain inherent rights, of which, when they enter into a state of society, they cannot, by any compact, deprive or divest their posterity; namely, the enjoyment of life and liberty, with the means of acquiring and possessing property, and pursuing and obtaining happiness and safety.

Can anyone point me to some sources that discuss what function the "defending life" language was understood as serving at the time -- or for that matter in the succeeding decades -- and why it might have been added?

While I realize bleggars can't be choosers, I'd prefer some relatively concrete evidence, rather than just general speculation about what the Framers must have thought during the Revolutionary War. Many thanks!