Unlike all the other systems of the body, the reproductive system has nothing to do with the well being, homeostasis, health, or survival of the body. The body can be quite strong and healthy without a reproductive system, as in the case of pre-puberty children who have non-functioning reproductive systems, women who have had complete hysterectomies, etc.

When we take this fact into consideration, having a reproductive system is actually a physiological burden. Also, the reproductive system is a common site of cancers (cervical/uterine, cervical, ovarian, breast, prostate, testicular, etc.), infections such as yeast infections of the vagina, venereal diseases, etc. Pregnancy itself is a huge drain on the health of the mother, especially in non-developed countries where diet and adequate health care are lacking. Remember that is was not uncommon for women to die during childbirth until around 100 years ago.

The drive to mate leads to death or injury for many animals. Some male preying mantids and spiders get eaten by the female of their species, either before or during mating. Male lions, moose, elk, etc. often die fighting other males for the mating rights to groups of females. Female sharks, tigers, and unfortunately some humans suffer wounds inflicted by their mates.

So comes the question—why do we have a reproductive system anyway? Well, the obvious answer is for reproduction—to have offspring. And of course, for humans and some other mammals, sex can be a very pleasurable activity, even when reproduction is not the goal. Sex is a major part of bonding intimately to another individual—Love, as we call it. But back to reproduction, why have offspring? We used to say “to perpetuate the species,” but that now seems to be the wrong answer.

It is now recognized by biologists that perhaps the most universal characteristic of living organisms is that they all seem to be after one thing. That one thing is called Biological Selfishness-or-Genetic Fitness. All organisms “strive” to get as many copies of their genes as possible into the next generation, and this is usually achieved by having offspring. In The Selfish Gene by Richard Dawkins (a great book!), the argument is made that genes are what life is all about. If genes are not passed on, they loose out in evolution. Those that are passed on are those that build the next generation of bodies. Darwin didn’t know about genes, but he did recognize the heritable effects of genes in bodies, and he saw that these phenotypes were obviously selected for-or-against in the struggle to survive and reproduce.

Organisms don’t try to perpetuate their species, they try to perpetuate their own personal genes. When a couple of male lions take over a pride of females (by fighting & often killing the current male pride holders), the first thing they set out to do is to kill any nursing cubs fathered by the ousted males. When this is done, the nursing females soon come into heat allowing the new males to mate with them and father their own cubs. The new males may kill males of their own species along with new cubs of their own species because they don’t carry their genes. In fact, they were hindering the biological selfishness of these new males, so they were eliminated. Lions obviously don’t care about the perpetuation of their species, only about the perpetuation of their own personal genes.

This pattern seems to fit for all organisms, though usually not through the violent means used by lions. However, studies in humans have shown that in families which adopt children, or where one parent cares for children of a spouse’s previous marriage, child abuse is 100 times more likely to occur as compared to families where the children are the genetic offspring of both parents. (Remember the stories of Cinderella and Snow White?—both abused by their stepmothers).

Even the few examples of animals that lack a functional reproductive system can fit under the concept of biological selfishness. Worker termites are sterile, yet they can increase copies of their genes by working for their mother and father (the Queen and King termites). All workers are siblings who share 50% of their genes in common with one another (just like human siblings). If the worker termites could reproduce, their offspring would be related to them by the same factor—50%. Instead of reproducing, the workers help Mom & Dad to have more sibs with the same 50% gain in gene copies. Workers don’t live more than a few months, so new sibs outlive those which worked to insure a healthy colony before them.

Some writers have referred to social insect colonies as superorganisms with the sterile workers and soldiers having the role of keeping the colony alive and healthy (like most of your tissues and systems) while the Queen and King have the role of reproduction (like your reproductive system). At least once a year, some of the newly formed termites are winged and have functional reproductive systems. These winged males and females fly out to mate and start new colonies—the “offspring” of the parent colony.

Dawkins called bodies “survival machines” created by the genes—and for the genes. Bodies help genes to survive in the environment and eventually to copy themselves into the next generation. Though we mostly concentrate our interests and attentions on individual organisms (which are short-lived in geologic time), evolution is really a genetic process whereby some genes (or alleles) succeed in being passed on at greater rates than other genes—for literally millions of generations. Most of our genes are identical to those of Chimpanzees. Some of our genes are identical to those of less-related mammals and other organisms. This shows that these genes have been copied and passed down for many millions of years into numerous species that have branched from common ancestor species.

It would not be scientifically incorrect to say that all your other systems are just support systems for your reproductive system, or that your whole body is just a complex support system for your genes. From the scientific stance, biological selfishness (genetic fitness) is what life appears to be all about, both in its everyday functioning, and in the long evolution of life on earth. This way of thinking seems very strange and uncomfortable to many, but it is very well supported by our scientific understanding of life on this planet.

Some humans, of course, are an exception. Some people have supplanted biological selfishness with social and material selfishness. Some people want more money, more power, more friends, mores possessions, etc. rather than more offspring. Even when people do want children, they are wise enough (sometimes) to understand that they can only support a limited number of them. BUT—since we have done a good job of overpopulating the planet with humans, it is obvious that humans collectively do have biological selfishness as a goal (not necessarily consciously), even with the numerous exceptions.

Humans have been on the planet for around 2,000,000, years (depending on how you define humans), yet it took until 1830 for our numbers to reach 1 billion. It took only 100 years to double to 2 billion in 1930. We doubled again to 4 billion in only 46 years (1976). Now we are somewhere around 6.7 billion and are driving other species to extinction on a daily basis (crowding them out). Dawkins wisely points out that what is natural is not necessarily good, and this should be obvious. Disease is natural—medicine is unnatural. For our species, we need to reduce our “natural” reproductive rate before we destroy even more of our living planet, along with any hopes that our grandchildren will inhabit a healthy world filled with a diversity of life (sorry for the sermon!).