There is no such thing, in anthropology, as a "caveman." Some early human groups lived in caves, yes; others lived in tents or huts or plain old houses. I guess there's a bit less of the primitive-romance ring to "houseman."
But if by "cavemen" we mean hunter-gatherers without metal tools or formal government, here are some things you should know:
1. These groups exist today.
When metal tools and agriculture were invented, not everyone took them up. Or they took them up and abandoned them. These were not irrational decisions--being an HDTV-owning Westerner may be more comfortable than being a hunter-gatherer, but being a subsistence farmer (or factory worker, for that matter) isn't necessarily.
So "cavemen" aren't purely a matter of speculation and pottery shards. You can go out and talk to some. Ask them about their freewheeling matriarchal pansexual utopia or their animalistic primal male brutality.
...No, neither is the case. It's impossible to generalize about hunter-gatherers since I'm talking about completely separate groups in different parts of the world, but none of them are nearly as wacky sexually as "cavemen" have been made out to be. A lot of them even just have marriages.
2. Everything we know suggests that anatomically modern humans were also mentally and emotionally modern humans.
The jokes are about cavemen going "ugga ugga FIRE ug," but a better quote from the Paleolithic would probably be "Good morning! Let's go fishing; I just traded some pots my wife made to the guys across the river for some bone fishooks. Now I better bring back some big fish or she's going to be mad." (In caveman language, of course.) They were people, living people's lives.
Obviously not all of their cultural values were in common with modern Americans, but we're talking like foreign-country different, not like chimpanzee different. (And while I'm at it: even chimpanzee different is not irrational or pointlessly brutal. Chimps have structured societies and they only express agression under certain circumstances and there are tons of examples of them putting social cohesion over physical urges. Even animals aren't "animalistic.") You might not always have agreed with them, but you would have understood them. And not like "the male is providing for his mate to prove his genetic quality" understood. Like "yeah, I can see why he kinda owes his wife after selling her stuff" understood.
Here are some things we know Paleolithic people did: Care for the sick. Bury the dead. Make art. Wear jewelry. Keep dogs. Travel in boats. Trade with each other. Follow calendars. Play musical instruments.
Boats? Boats that could get to Australia. You take some trees and some rocks and sail to Australia. (And when you get there, ain't exactly a Foodmaster in the neighborhood, so you're going to have to pull some Bear Grylls shit. For your entire life. While raising children.) Then tell me about primitive cavemen following their animal instincts.
3. Human culture changes much faster than the human genome.
I mentioned above that hunter-gatherer groups are quite different from each other. Someone from the Pirahã people in the Amazon wouldn't have all that much to talk about with someone from the Sentinelese people in the Andaman Islands. But the genetic differences between them--and between either of them and you or me--are extremely slight. Their culture was shaped by their circumstances and their history, not by genetics.
So to call the process by which other hunter-gatherer groups started farming and specializing and forming civilizations and colonizing until they became you and me "evolution" is a gross misuse of the term. It's sure as hell not genetic evolution, at least. People who farm don't dominate the world because there's a "farm gene" that has become prevalent, but because farmers had more children and they taught those children to farm. Farmers having more kids is NOT "survival of the fittest" in the Darwinian sense; if you raise one of those kids in a hunter-gatherer society, they're not going to spontaneously plant a garden.
Things that are way, way too new to be codified in the human genome:
Dating (arguably, my grandmother is older than modern dating)
Groups of people larger than your high school graduating class
2011 standards of physical beauty (again, ask my grandmother)
Behaviors relating to these or other modern concepts are extremely, extremely unlikely to be directly "hardwired" into our genetics.
4. You are not a caveman, anyway.
Yeah. Don't sit there at your computer wearing your pants enjoying your central heating and tell me that sexuality is the one specific area of human behavior where people are helpless against their genetics.
Slightly off the caveman topic, but a thing I wanted to say:
5. Physical beauty does not indicate "quality genes" and sexual frequency does not indicate "fitness."
"Fitness" means the number of children you have who survive to reproduce themselves. To a lesser degree, the survival and reproduction of your other relatives and your tribe also increases your fitness. So being kind and responsible to your family isn't just ethical, it's adaptive. Considering the amount of work involved in raising a human child (particularly in preindustrial times), conceiving a bunch of embryos and running off doesn't necessarily get you a lot of grandchildren.
As for the "quality" of a hottie's genes, all you can really say is that the children are more likely to be hotties themselves. Doesn't make them more (or less) fertile, intelligent, healthy, aggressive, cooperative, or good at parenting. Mating with a square-jawed broad-shouldered dude who carries genes for asthma and has no malaria resistance is no way to ensure "quality" genes. That'll just get you a bunch of square-jawed broad-shouldered kids with asthma and malaria.
It may be super boring to suggest that being in a stable relationship with someone who's nice as well as healthy is the "fittest" thing for both sexes, but I think it's a hell of a lot better bet than a supermodel fucking an egomaniac.