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Spiders do it. Salmon do it. Even fig wasps do it. They reproduce and then die right after. But humans wouldn't die to have sex...or would we?
Salmon are famous for swimming upstream, against the flow of a river, to find calm waters to reproduce. Even more amazing is what happens next. Do the happy parents go home after the females lay their eggs on the river bed, and the males fertilize them? Do they swim the easy way down the river, returning to their comfortable feeding grounds? Or do they perhaps hang around to see the younglings grow? Far from it. Instead, the salmon lose their energy for life. Both the males and females slow down, weaken, and die. It is not exhaustion that kills the adult salmon, as was once believed. They die because it is their nature to die. They die from many problems, like ulcers and infections, but these problems all come from a single trigger: chemical changes in the salmon. They come from the same hormone changes that drove the salmon upstream in the first place! The salmon are literally programmed to travel upstream, reproduce, and then die.
The salmon are not alone. The squid, the octopus, and many other creatures follow the same pattern. They are part of a large family of creatures called semelparous organisms that have offspring only once in their lives and die right after. Male spiders regularly risk life and limb in approaching the much larger females. A female spider will hopefully be in the mood to mate. If not, she may be in the mood to eat, in which case she will eat the male. Spiders are both carnivores and cannibals. The male must convince the female to mate. It becomes a matter of life and death for him. For some species of spider, the females have their cake and eat it too--literally. Even when the male spider wins over the female and mates with her, she will still turn him into a meal.
How about humans? Would you choose to die so you could have children? Or course not...or would you? In fact, there are many examples of people who seem to put their lives at risk to have sex.
In Afghanistan, where medical care is scarce, pregnant women cannot easily get the treatment they need. If complications arise during childbirth, the results can be devastating. It is estimated that one birth in every fifty will end in the death of the mother. Women around the world regularly sacrifice their slender physiques and often their careers to have children. In Afghanistan and other less developed countries, they also risk their lives.
In the African nations of Botswana, Swaziland, Zimbabwe, and South Africa, over twenty percent of the adult population is living with the killer AIDS illness or the HIV virus that eventually causes it. That is one in every five adults--a large and horrific number. The main cause of infection is heterosexual activity. In the regions with the highest HIV rates, it is estimated that one teenager in every three will eventually die from AIDS.
The message is clear. Your animal brain--your subconscious mind--is willing to risk your life, just slightly, for reproduction. This does not mean to say that reproduction is wrong. It only means that sacrifices are made between the basic instincts. In this case, the tension is between the first two basic instincts: survival (as an individual) and reproduction. As ever, understanding your brain and basic instincts will give you the tools to make the best decisions.
Let's take a deeper look at the relationship between survival and reproduction by investigating their origins. The early creatures on the planet were microscopic, single-celled organisms. Some of these tiny creatures only lived for a short time. They had a survival instinct, but it was literally short-lived. Other creatures were different. They could cheat death, in a way. They could reproduce themselves in a process called asexual reproduction. These creatures were the early hermaphrodites. They were not male or female--meaning that they had no gender. In fact, they needed no partner to reproduce. They just reproduced by themselves, all alone. Today there are many examples of hermaphrodites in the animal kingdom. They are usually small, simple creatures like worms or fungus.
Yet another set of those early creatures were different. They developed a simple kind of sex to create new creatures. They did not reproduce alone. They joined with a partner, in a process called "conjugation." When they came apart again, they had exchanged some material from their bodies. Shortly after, they each split in two. They used their shared materials to create a pair of new creatures. This last step is called "fission," but you can see how it is a simple kind of childbirth. By coming together for a short time, sharing some bodily material, and creating new life, the two creatures had, in effect, cheated death. An ancient kind of reproduction was born in these simple creatures. Even after they died, they would also stick around, in a way. They would continue to have an impact on the world, even after their bodies were gone and their lives as individuals were over.
For over a hundred years, scientists have believed that sexual reproduction makes evolution more successful. Unlike asexual reproduction--without a partner--sexual reproduction causes many changes. Each new generation is different from the last. In other words, it leads to genetic variety. A team of scientists from the University of Auckland, in New Zealand, recently set out to prove this theory. They tested two kinds of the yeast fungi, one that could only reproduce asexually and another that could reproduce sexually, with a partner. The two types of yeast were then forced into difficult conditions, for example by taking away their food. Under these conditions the researchers found that the sexual yeast did much better. It was able to grow, while the asexual yeast failed. According to Dr. Matthew Goddard, "It shows, without a doubt, that sex allows for more rapid evolution."
Of course, there is a lot more to reproduction than just sex. Reproduction for humans is not just about finding a mate and performing a short-term act as it is for salmons and spiders. It is a long process that includes raising children, keeping them safe, and teaching them the skills to survive on their own. It includes teaching them cooperativity, so they can succeed within their own groups. In some cases, reproduction for humans even means teaching children religious rules, because in some communities it might be deadly not to follow the local religion. The love a parent feels for a child is genuine. It is powerful. It is real, but it also serves a purpose. Humans would not have survived without parental love. Humans slowly, but surely, evolved this love. Early humans who did not feel such love had a greater chance of failing. They may have survived as individuals, but their children often did not. Since their children carry their genes, it means their genes often failed to survive. Through natural selection, their genes were eventually eliminated.
In 1972, Robert Trivers wrote one of his ground-breaking papers, called Parental Investment. In it, he describes how and why parents give so much to their children. Parents choose how best to invest their time and energy while making sacrifices along the way. So, as you would expect, the tension between individual survival and reproduction can be seen across the entire spectrum of parenting activities. Recent discoveries provide a stunning example of this tension...during pregnancy.
Even before a baby is born, it makes demands on the mother. Its placenta produces a hormone called allocrine. This chemical enters the mother's bloodstream and gets her body to put more sugar into her blood, which also flows to the baby. This benefits the unborn baby who feeds on the sugar, but too much blood-sugar is not healthy for the mother. She is at risk of developing a condition called gestational diabetes, so her body produces insulin to bring sugar levels back down again. Almost like a tactic in a game, the unborn baby makes another move. The placenta contains special cells that detect insulin. A rise in the mother's insulin level causes extra allocrine to be produced by the placenta--a move designed to get sugar levels back up again. The conflict between the two--individual survival and reproduction--highlights the complexity of human life. It starts with a chemical battle within the womb, but it can last a lifetime.
Despite the tension between the first two basic instincts, they ultimately work together. They create the chain of life. Four billion years ago, bacteria signaled the start of life. One billion years ago, the early, single-celled creatures appeared. Some of those creatures were special. They could pair up to create new creatures, and that meant the start of reproduction. They eventually evolved into a wide variety of species--the creatures you see around you today--including mammals. Only through reproduction could genetic variety have become so rich. Only through reproduction could such special creatures have evolved. The early organisms that could reproduce were our ancient ancestors. The two basic instincts of survival and reproduction have been working together ever since. They teamed up a billion years ago as partners in the game of life.
* Includes excerpts from The Third Basic Instinct.
