It's an interesting question (definite upvote), but there's no reason other than inertia to think sat fats have anything to do with it. There could be many different reasons for the gap -- and the gap may not be a bad thing anyway. After all, if you graph total cholesterol versus total mortality instead of just CHD, the sweet spot for modern humans seems to be about 190. Above 210 or so, the curve starts to climb from CHD, but below 160 it climbs pretty fast from causes like stroke and suicide. So 110 may not be a good goal for us anyway; for whatever reasons, when we're in the least danger of death, our cholesterol happens to average about 190.
If you see cholesterol not as a poison, but as the building block and repair substance it is, this becomes a very different question. Then it's not, "Uh oh, maybe our cholesterol should be lower"; but instead, "What is all this cholesterol doing for us?" It's like seeing a car with Bondo all over it. The Bondo is a good thing. It didn't cause the car to rust; it's holding the car together. But you have to wonder what caused the car to need so much of it in the first place.
Musing about some other possible causes:
Sunlight. Sunlight turns cholesterol into D, and HGs probably spend more time in the sun than we do, and they don't use sunblock (except the natural sunblock of a tan, which doesn't stop D production). Maybe they keep more of their cholesterol converted. I noticed that the Inuit and night monkeys have the highest levels of their respective groups, and they probably get the least sunlight (if "night monkey" means what I guess it means). That's one data point of correlation, for what that's worth.
Sleep. HGs probably sleep on a more natural rhythm, waking up with the sun and going down with it, and almost never staying up all night drinking coffee and cramming for an exam. Lack of quality sleep is a major:
Stress, especially constant, chronic stress. Sometimes I'll stop in the middle of the day and realize my entire body is clenched, especially my face, and I'll take a few minutes to just relax -- stop squinting, roll my shoulders back, etc. I don't have a high-stress job or anything; I'm just a normal guy trying to keep up with ordinary modern life, paying the bills, getting places on time, and keeping track of who needs what from me. But it adds up, and it's always there wearing at a person, especially mentally, which brings up:
Brains. The brain uses a lot of cholesterol. I wonder if anyone's done a study comparing brain size to cholesterol levels. I don't know how much modern man's brain size and structure differs from the average HGs, but aside from that, we use our brains differently to handle all those modern mental stresses. Maybe that has caused our brains to ask that we have a higher reservoir of cholesterol to draw on. (Although horses, if their actions are any indication, have brains the size of a walnut, so this may be contraindicated.)
Pollution, from unfamiliar chemicals in our food -- even good food -- to stuff in our air, homes, and vehicles that HGs don't have to deal with. Since cholesterol is used to repair some kinds of tissue, maybe we need more of it to repair damage caused by substances in our environment that are unique (or unique in their quantities) to modern man.
Diet. For all that we avoid the "neolithic agents of disease," most of us probably don't eat a lot of bugs or drink our water straight out of streams. We can mimic a HG diet to some extent, but it'd be pretty hard to duplicate it without actually becoming a HG.
I could probably come up with more, but I'm running out of time (see, more stress). I think the take-away from all this is that we're different from HGs -- not so much biologically (though that's true in some ways) -- but our lives are very different in a variety of ways. That higher cholesterol may be helping us deal with those differences. As you suggest, if we went back fully to a HG lifestyle and environment, maybe after some generations our cholesterol would sink back down to 100 or so. That probably doesn't have much application to reality, though.