On the parasite topic:
This is also part of why traditionally eaten raw meats are cut very thinly. One should inspect the meat through a light source (called "candling") for eggs and other goodies. Keep in mind that our ancestors were almost certainly battling parasitic infections. Dr's Eades talk about this in Protein Power Life Plan, as does our own Greg Everett with regards to potentially unhealthy levels of iron.
Now the topic of Paleo longevity was well addressed by Scott K but I'll add that average lifespan, stature and dental health all suffered with the advent of agriculture. Infant mortality greatly increased which should beg the question then: How did our global population increase with the advent of agriculture? Not only was a greater caloric density available but birth spacing shortened from an average of 4.5 years for hunter gatherers to 12 months for agriculturalists. Elevated insulin blocks the contraceptive effects of breast feeding, thus allowing for much more frequent births.
This is off topic but if you start talking population and sustainability it appears that your best bet is to industrialize and educate your population. This will encourages higher yield agricultural practices (whether paleo-esque or not) AND it leads to dramatically decreased birth rates (bad secular humanists not wanting 6 kids!)
The Neo-Cons think this will lead to Islam overrunning Europe and the destruction of The West. I guess time will tell.
"Survival will be neither to the strongest of the species, nor to the most intelligent, but to those most adaptable to change."