"We" are subject to survivorship bias. Plenty of people did not make it and their bloodlines are long extinct.
The difference between Stone Age and today is that our civilization managed to conquer most really serious risks that used to shorten the lives of people under, say, 70. Famines, unsafe water, most bacterial diseases are well under control. So, of course, the roster of threats now changed, some of them being civilizational (road accidents), some of them being relatively small holdovers from the ancient days, such as STDs, plus the very aging that makes our mortality curves shoot up in the old age.
But yes, realistically, people are going to bareback one another all the time. Which means that vaccines and cures for whatever bug is transmitted like that are necessary.
The difference between Stone Age and today is that our civilization managed to conquer most really serious risks that used to shorten the lives of people under, say, 70. Famines, unsafe water, most bacterial diseases are well under control. So, of course, the roster of threats now changed, some of them being civilizational (road accidents), some of them being relatively small holdovers from the ancient days, such as STDs, plus the very aging that makes our mortality curves shoot up in the old age.
But yes, realistically, people are going to bareback one another all the time. Which means that vaccines and cures for whatever bug is transmitted like that are necessary.