While it's generally accepted that sexual activities should be personal private matters between willing adult participants, our obsession with sex has always exerted a powerful influence on our social systems and even the character of our civilizations. In this age of accelerating change, it's hardly a surprise that we've been experimenting with the sex related aspects of society, just as we've tinkered with the political and economic aspects.
Driven by a desire to deny the more primitive aspects of human nature, or to "right" a misunderstood "wrong", we've perhaps too eagerly abandoned the wisdom of the ages, and tried to convince ourselves that we are somehow different from those who came before us. Most dangerous to society is our modern obsession with change, which in a growing number of us has become a desire for change simply for the sake of change. This simple minded desire for change, coupled with a lack of understanding of what is being changed, too often results in abandoning the hard learned lessons of the past in favor of repeating forgotten failures simply because they offer a change.
There are currently serious efforts to arbitrarily redefine long standing concepts like sexual orientation, gender roles, and long term pair bonding (marriage) that evolved over thousands of years, without considering the fundamental roles these concepts have played in society and the evolution of our species. As a result of demands to blur sexual definitions as a way to "fix" superficial perceived injustices or inequalities, these issues have now become the subject of a national debate that is most remarkable in its near complete absence of anything even faintly resembling a rational consideration of the actual role of sex in our society.
Human sexuality has two primary purposes from the perspective of evolution. The first is the same instinctual drive to procreate that is common to most animals. If humans were like most animals, we could get by quite well just responding to pheromones or other indications that a female was in heat. Women would only come into heat during the most appropriate season to have their baby(s) in the spring.
But our evolutionary path has created complications that last long after birth, and required a modification of our sexuality. Yes, all of our problems with sex are in our minds - or rather are a result of our minds. One major problem with evolving a large brain is getting it through the birth canal. Another other problem is also our greatest strength - we evolved as a generalist species lacking a preprogrammed adaptation to any specific environment. As a result, human children must be born only partly developed while they're still small enough to squeeze out the birth canal. They also require an extended period of intensive dependency (childhood) while they mature physically and learn how to survive in whatever environment they've been born into.
In those species where the male's involvement is limited to mating, it's generally in the male's best interests to sire offspring with as many females as possible. But human children require a far greater parenting investment than simply providing them with food until their fangs or feathers mature sufficiently for them to find their own dinner.
In the primitive world where day care centers, grocery stores, and modern kitchens are notably lacking, providing optimum parenting and provisioning for the typical horde of children was usually more than a full time job for a single parent. In a complex society involving complementary gender roles, the presence of parents of both sexes also provided valuable role models and experience dealing with the opposite sex. Other members of the tribe no doubt contributed to raising the tribe's children, but over the long term, those children who were directly supported and educated by parents of both sexes tended to have better odds of survival and reproductive success.
Humans needed a way to sustain a long term monogamous pair bond, and the instinctual bonding that works for lower animals wouldn't be adequate for a species with an intellect that habitually interferes with its instincts. The mothering instinct is well established in most animals, and it wouldn't have taken much of an adjustment to get to the level of bonding between a modern human mother and her children. The evolutionary objective then becomes involving the male in the long term parenting of his children. And as so many have already noticed, the key to "influencing" a human male's behavior is sex.
During the rutting season the sex drives of the males of many species largely override their other instincts - including those that would be in their individual long term best interests. However, I have a hard time seeing a direct evolutionary path from the mating behaviors of animals to the recreational sex of humans. It appears to me that the evolutionary path to our current state started with human females coming into heat more often in order to keep males effectively in a perpetual rutting season, perpetually focused on convincing the females to allow them to have sex.
Having established frequent mating as a means of keeping the male interested in the female, transforming frequent mating into recreational/pair bond enhancing sex then becomes largely a matter of relatively minor adjustments to existing functions and responses. Add in a couple hundred thousand years of evolutionary distortions resulting from our artificially complex group dynamics and compulsive intellectual interference with any trace of "nature" we find in ourselves, and you get modern sexually confused humanity. We're instinctually driven to want sex all of the time, but we no longer remember why.
A further source of complications is the layered manner in which our sexuality is defined. Our physical sex is primarily defined by genetics. The next layer takes the starting point of the individual's genetically determined sex and layers on the effects of the complex hormone environment of the mother's womb. The particular mix of male and female hormones the fetus experiences during gestation largely determine its basic sexual orientation, as well as a number of other secondary sexual characteristics - tomboy to ultra feminine in females, effeminate to macho brute in males.
Our sexual orientation isn't genetic, but we're pretty much committed by the time we're born. If the hormonal exposure is appropriate for the fetus' genetically determined physical sex, an individual will be heterosexual. If an individual is exposed to the wrong hormone mix during gestation, he/she will become homosexual. At least in basic orientation.
The hormone influence continues after birth from the internal primarily genetically driven glandular processes, but the most important stages have already passed, and the individual's basic nature is already set. All that remains is to associate the genetically and hormonally determined sexual orientation with a particular target type.
Sexual associations tend to result from learned behaviors and childhood experiences. In a primitive society individuals learn to be attracted to whatever standards of attractiveness their local group has adopted for their sexual orientation. Our modern media driven society greatly confuses the process of learning sexual associations by offering multiple contradictory and even destructive alternatives.
Since we learn how to express our sexual orientation, we can in theory change the ways in which we seek to express our sexual orientation. It's not uncommon to start out seeking one type of partner, and learn to be sexually attracted to a whole different type in response to factors like availability, irrational emotional attachments, money, desperation, etc.. While some learned sexual associations can be very flexible, some appear to be very resistant to intentional alteration. For example, sexual associations involving children and/or violence resulting from childhood traumas are reported to be effectively beyond the reach of current treatments.
So basic orientation isn't a choice. We can choose to attempt to struggle against our basic sexual orientation just as we can try to overcome our basic natures in other areas of life - and with likely as little success. We have some control over our learned sexual associations and the manner in which we express our sexual orientations, but likely only as much control as we have over the other aspects of our personalities. Some of us have a great deal of intellectual control over who we are, while others appear to have almost none.
The concept of traditional marriage grew out of the existing physical and emotional dynamics of pair bonding as a way of formalizing the long term support of children. As material wealth increased the potential for inheritance beyond bits of chipped stone and a few poorly tanned animal hides, marriage also reinforced the attachment of grown children to the family unit, and tended to encourage their reciprocal care for their parents as evolving group dynamics and technology improved life expectancies.
The importance of sex to long term pair bonding, and the resulting increased odds of successful reproduction, was the foundation of the traditional requirement for sex within marriages. A high reproductive rate was a primary necessity for the survival, let alone prosperity, of primitive societies. High infant mortality rates and short life expectancies required a steady flow of replacements. Increasing the group size was a primary means of improving a primitive society's ability to defend its territory and increase its prosperity.
Marriages that involved sexual relations were of significantly greater value to early human societies since they tended to produce a greater number of successful offspring. Marriages that failed to produce offspring, or which failed to adequately nurture their offspring into productive members of society, were a waste of a primitive society's limited resources.
The gestation, birthing, and nursing processes already provided females with very strong attachments to their children, and their less obsessive sex drives already gave them a fair amount of power over males. It only takes a slight imbalance in sexual appetites to make one side the ever hungry beggar and the other the entirely satisfied reluctant supplier. So it was natural for the concept of marriage in the primitive world to focus almost entirely on guaranteeing the male with enough sex and status within the family unit to keep him involved in supporting and parenting his children.
But what worked in the primitive world becomes a source of unnecessary social distortions and pending ecological disaster in our modern human dominated world. We're just starting to realize that our overpopulated world is running out of room for the results of our continuing efforts to encourage high reproductive rates. At the same time, our progressive shift from emotion and instinct to intellect has redefined our most fundamental perspectives on the purpose of life. We no longer consider success to be simply living long enough to ensure the next generation a good start. Now we consider the act of living itself to be the purpose of our individual lives. For many modern individuals, having and raising children has been demoted from their primary purpose to just another minor distraction in an otherwise intellectually fulfilling life.
Our society has lagged behind in accommodating changing social attitudes in its structures and practices. We continue to respond to our long adaptation to pair bonding, but we've drifted a long way from connecting our pair bonding with raising children. We've redefined pair bonding to be nearly any sort of relationship between two or more individuals - including members of the same sex. Since society is no longer desperate for new citizens, the decoupling of pair bonding and child raising no longer threatens the survival of the species. In fact, in an overpopulated world, pair bonds that don't produce additional population growth become more of a solution than a problem.
However, we continue to provide artificial advantages to those who are officially designated as "married", and it's almost entirely these artificial advantages that are driving the demand to recognize nontraditional pair bonds as marriages. The preferential tax rates, health insurance coverage, welfare, etc. are all effectively wealth transfers extracted from single individuals in order to subsidize those raising the next generation.
Forcing those who choose to live as singles to subsidize those who choose to live in nontraditional pair bonds is entirely unjustified both rationally and ethically. Nontraditional pair bonds have never before required subsidies from the single members of society to facilitate their formation. Nor do nontraditional pair bonds provide society with critical functions that justify the sort of social distortions and forced wealth transfers that we have historically provided to reproductive pair bonds.
It will remain entirely inappropriate to expand the legal definition of marriage to include nontraditional pair bonds as long as society continues to artificially subsidize marriage. But we should also be reconsidering whether the marriage subsidy should be continued even for traditional pair bonds. It makes little sense to maintain the current subsidy for marriages as a means of subsidizing those having children now that we should be encouraging reproductive restraint in an overpopulated world.
With the exception of legal marital status, only those aspects of nontraditional sexual orientations that cause harm to others should of concern to a free society. If homosexuality is largely the result of malfunctions in the hormonal environment before birth, no amount of persecution by straight society is going to do anything but drive homosexuality underground, and create unnecessary friction and hostility. The worst possible response to homosexuality is to create an artificial perception of "us vs them" since this only encourages the worst elements in each segment of an increasingly balkanized society. Society should neither encourage nor discourage any sexual orientations or pair bonding patterns that solely involve willing participants of legal age.