What were the sexual habits of our paleolithic ancestors like? Did they primarily have one partner, or various partners? Were they more sexual in Spring then Summer, or sexual in all seasons like modern humans? Was it everyone for themselves? How do these sexual habits of our ancestors influence us now?
I did a post about our promiscuous heritage recently after reading Sex at Dawn. It's funny because that knowledge makes me MORE committed to monogamy, or at least serial monogamy. The truth is that STDs and unplanned pregnancy are a real worry these days. But the benefits of "unprotected" sex and the detriments of birth control are also very real. I definitely think that it's healthier physically and mentally to have large amounts of real sex with one partner who you are in a committed and stable relationship with than to load your body up with hormonal pills to have plastic "protected" sex with a bunch of people.
Either way Sex At Dawn is a great read.
Oh, goodness. Well, the jury is certainly out on this one (these ones? you posted a lot of different habits to address), and probably will be for some time. For a few examples,
evolutionary psychologists seem to be leaning towards polygamous and frequent sex-- with also a whole lot of monogamy in between. Some researchers have pointed out that the human male testes size is right in the middle of testes size for primates, and there seems to be a scale: large testes = polyamorous, small testes = less so.
No one really knows why female genitalia "moved" to the front. Some believe it may have even precipitated the development of language, as men and women were forced to communicate.
No one is really sure why female sexuality seems more fluid and aroused by more things (watching both males, females, and animals having sex) than male sexuality. Some attribute it to protective measures--so that the female is always 'ready' to be penetrated, whereas others point instead to the social structure of our bonobo relatives, which includes inter-female sexuality.
Some think children were raised nuclearly--that is, by a monogamous couple--whereas others think children were raised more communally, since it would have been difficult to discern who the father always was. Others, of course, assert that both of these possibilities were probably practiced.
Some researchers propose that rape was an evolved mechanism to spread seed. Other researchers really don't like this one.
I'm sorry I don't have citations for any of these. I could probably find a few. But if you want a reliable source I would check out any of the pop sci books out there today, or also this book: http://www.amazon.com/Evolution-Human-Sexuality-Donald-Symons/dp/0195029070 (pricey). Or this: (more accessible):http://www.amazon.com/Evolution-Desire-Revised-4/dp/046500802X/ref=pd_sim_b_1
As a final caveat, evolutionary psychology in and of itself is on a wire these days. Post modernist society questions (condemns?) the cultural context from which we all look back on our acestors, and in particular condemn gender norms for skewing our biases. Its hard to see human nature in the past clearly when we don't really have an understanding of human nature in the present.
I see that Sex at Dawn has already been recommended a few times. The central thesis of that book being, that, for most of our history, humankind was essentially non-monogamous; if you accept that premise, I would recommend "Opening Up" by Tristan Taormino for a good primer on living a modern polyamorous life. Its not as scary or risky as some folks may think.
Unfortunately, there's no way to really tell who was bonking who in what combinations, permutations, and frequencies, from the fossil record. Odds are we did what we do now, which is a majority of people hew to whatever the cultural norm is, and rather a lot of people don't. And those norms probably varied quite a lot. And there would have been a lot of gossip, and jealousy, and the odd fight, and, well, observe your local dating scene, whether it's singles bars or church socials. I think that "human mating practices vary widely" is about the only completely safe generalization you can make in this area.
As for seasonality, well, it is possible to have sex while winter camping. And in the spring, there are a lot of biting insects about. And this all varies according to climate anyhow. I think we're just wired to get as much as we can whenever we can.
There's a great little Aussie film called Ten Canoes that tells a story about love among pre-contact Australian Aborigenes. The story involves two brothers, one who has three wives, the other who has none, and wants his brother's third wife. It's probably pretty speculative and I wouldn't want to assume that its representations of Aboriginal sexual practices and morality is accurate, but it is worth a watch.
Hard to guess, but if you look at current tribes, there are trends. Most have bonded pairings/marriages that are supposed to be monogamous. In many, the pairings are arranged by parents/relatives. The men often have more choice than the women and play around more than the women. Sometimes, a dowry is paid either by the man's family or by the woman's family. Often, the woman goes off to live with the man's family or tribe, but not often the reverse. Women typically get paired off right around puberty.
I also saw one tribe in which sexual playing around outside the marriage was actually considered normal and allowed, but this does not seem to be the norm in many tribes.
I think we can only guess from what we see in various tribes now and in their recent history how it might have been further back. Since tribes vary greatly now, there was probably also a huge ton of variation back then. HOwever, each tribe would have had to work out a situation that allowed the tribe to thrive. But apparently, there are many ways that this can be done. I would guess also that the environment would effect how things were run. Nomadic peoples in areas of sparse resources would probably have set up their social system differently than people in say a rich tropical environment that allowed more of a stable village life.
I would say like most things its a bit of both and everything in between...
One good indicator of monogamy vs polygamy is the size difference between males and females, when the male is much larger than the female he typically has many partners, when they are of similar size you tend to get monogamy...
But as recent studies of "life long monogamous" birds has shown, appearances can be deceiving! I beleive both females and males in a partnership do "wander" at certain times of year or circumstances.
I think almost certainly there was a typical nuclear like family (we have evidence for this in burials) but also a lot of fooling around going on! Remember we are them, they are us! Indefinitely is incredibly common, and I am sure most men can attest to the fact that even being head over heals in love doesn't stop the blood pumping and inappropriate thoughts at the siting of a sexy reproductivly able random female ;)
Other than curiosity, you need to think about why you ask this question, and how you choose to apply the answer, if you ever get one.
Whatever sexual practices may have been, this is one area that may not transfer to the present like a good evolutionary diet does.
Society today is not the same. Sexually transmitted diseases are not the same.
Today we have culture, ethics, morality, and an expectation of honorable treatment. The fact that some people, and my soon-to-be-ex-wife in particular, exhibit none of these, makes them no less important.
Perhaps more so. Today's tribes are often 2 plus children. If you can't trust your partner to watch your back, and protect you from STD's via monogamy, who can you trust?
I haven't read any of the literature on this topic. A lot of smart people think our ancestors were rather permiscuous by modern standard. The question that comes to my mind is: If they really were polyamorous, how did they deal with potential inbreeding? A few years back I went to a part of southwestern China where there lives small group of people who practice a form of loose polygamy. A woman I met who was studying this and similar groups said inbreeding had been a problem.