In 1875, parliament raised the age of consent to 13; Life expectancy was about 40 as in in 1885.
Given our life expectancy, we should be RAISING the age of consent. Either that or my wife's cooking magazines are right and the hormone/antibotitic/genetic crap we are eating are making our kids mature earlier.
Only because of higher infant mortality. Those who survived past childhood had about the same anticipated lifespan.
I think you may be confused about lifspans in Rome. Let's leave aside that a very high percentage of babies were intentionally killed, which would dramatically increase mortality. Here's an interesting table. Seems awfully precise for a period about which we have limited data, though.
http://www.richardcarrier.info/lifetbl.html