Evolutionary Theories of Aging

In the 1800s, as scientific ideas triumphed over religious ideas, scholars stopped speculating about the existence of a soul and began speculating about the workings of the mind instead. By the end of the century, the formulation of theories about the mind and the search for evidence to support these theories had become the formal science of Psychology.

There has been, however, no easy path to progress. The mysterious inner workings of the mind sometimes appear to be impervious to any kind of scientific approach. The functions of the brain are not something that can be easily observed in a laboratory. Not much can be learned from simply dissecting a human brain.

Despite more than a hundred and fifty years of progress in the field, researchers have not yet been able to formulate a model of the human brain that everyone can agree with. Instead, there are several popular models competing for dominance, and the supporters of each model are having trouble understanding each other.  


Some of the earliest investigations into the workings of the human mind were carried out by anthropologists in the late 1800s as the western world came into contact with many diverse cultures around the world.

At first, European anthropologists believed that foreigners (especially native tribespeople) who behaved differently from their conservative Christian culture were either biologically or culturally inferior. Many believed that human culture was evolving from a state of savagery to civilization. Many also believed that this was the will of God.

Later, American anthropologists developed a different way of thinking. They saw that all human beings were more or less the same, and that our behavior generally adapts to make the most of our local environment. Whether we live in the rainforests of Brazil or on the cobblestone streets of London, we are all products of our environment, more or less.

Anthropologists have continued to record the laws, languages, and lifestyles of people from all over the world, especially native tribespeople. These anthropological ‘ethnographies’ form a rich database of information containing valuable insights into human psychology.  

Freudian psychology

One of the first psychological theorists to capture the popular imagination was Sigmund Freud, who declared that almost every aspect of our personality stems from the way we reacted in early childhood to our own sexual instincts and to the sexual instincts of our family members.

One of the reasons for Freud’s success was probably because he appeared to be taking a scholarly approach to controversial topics that had long been taboo. Unfortunately, as his career took him to ever greater heights of influence, his writings grew increasingly speculative until his theories no longer resembled reality. Nevertheless, Freudian psychoanalysis continued to grow in popularity until it reached cult status in the 1960s. Freud’s followers can still be found today, trying to stretch his theories to explain every kind of observable human behavior.

Freud’s line of thinking led many people to believe that the human mind is divided into distinct operational components with names like ‘the ego’, ‘the identity’, and ‘the subconscious’. This line of thinking continues today in many forms, such as ‘phenomenology’, which ignores the biological workings of the brain and focuses instead on the inner experience of being conscious.

Most scientists, however, understand that people have been speculating about their inner experience of consciousness since before recorded history, and that such introspective speculations almost always lead to mystical or otherwise unscientific explanations.

Although Freud’s theories are still respected within their historical context, they are no longer considered to be good science. The reason they seem to have remained influential for so long, is because like religious myths, although they cannot be proven, they cannot easily be disproven in any way that would be readily accepted by their believers.  

Behavioral psychology

In the first half of the 20th century, while some researchers were being drawn towards introspective cults, other more scientifically-minded researchers were working to transform psychology into a highly disciplined science by gathering reliable information through repeatable experiments under controlled conditions.

However, when it came to devising experiments, many early researchers realized that there was no easy way to directly probe the inner workings of the mind, so instead, they concentrated on studying the easily observable external behavior of both animals and humans.

Researchers quickly confirmed that when an animal was rewarded each time it performed a certain behavior, it would perform the behavior more often. If the reward was then withheld, the animal would perform the behavior less often. Likewise, an animal could be discouraged from behaving in a certain way through punishment. By controlling rewards and punishments, you can shape the behavior of an animal or person.

The conditioning techniques developed by behavioral psychologists in the mid 1900s proved to be very effective, not only for teaching animals how to do tricks, but also for treating human disorders like autism and antisocial behavior. The results of conditioning research have since been enthusiastically embraced by educators, law enforcement officials, and marketing professionals.

The study of observable behavior led some scientists to conclude that we mostly behave the way we do because each type of behavior that we exhibit has had certain consequences during our childhood and throughout our lives. For example, if a particular behavior pattern attracted the admiration of your family members during childhood, then you will be likely to carry on that behavior into adulthood. You will continue to act that way in the expectation of some reward.

Other than confirming the common sense logic that much of our behavior is shaped by how we have learned to respond to our surroundings throughout our lives, there is not much else that behavioral studies have been able to confirm with any degree of certainty.

The problem is that for almost every imaginable experiment, there are almost always too many uncontrollable variables. Often, the best that can be done is to perform surveys and attempt to draw vague conclusions from rough statistics. Even then, the possibility of cultural bias always adds doubt to any claims about the discovery of universal psychological truths.  

Developmental psychology

Other paths of research also occasionally provide insights into the inner workings of the mind. Developmental psychologists, for example, have studied the changes in awareness that take place as a baby grows into a child and then into an adult.

By studying childhood development, researchers have convincingly demonstrated that some mental abilities develop before others, indicating that there is a definite path to mental development.

However, they have not yet convincingly concluded whether the development of mental abilities occurs in conjunction with the physical growth of the brain and its structures, or whether new mental abilities are learned from the environment as a child experiences one significant realization after another.  

Split brain experiments

In the early 1960s, after experimenting on animal brains, neurosurgeons discovered that life-threatening cases of epilepsy could be treated by slicing through the part of the brain that connects the left and right hemispheres. Patients could be cured of their seizures, but the two halves of the brain now operated independently, each with its own separate mental processes.

It was discovered that each half of the brain controls the opposite half of the body and that they each draw sensory input from one eye and one ear.

Generally, only one side of the brain has a good understanding of language and will have the ability to speak and write. In 95% of right handed people and 70% of left handed people, this will be the left side of the brain. By directing questions to this half of the brain, it was discovered that language skills are vital for logical and analytical thought processes.

The other side of the brain, usually the right side, specializes instead on interpreting visual imagery. It is also better at comprehending emotions. By directing questions to this half, it was discovered that understanding visual imagery was vital for conceptualizing how things work.

While the language dominant side of the brain focused on specific details, the visually dominant side of the brain was much better at seeing the whole picture.

In a few split-brain patients, both halves had a good understanding of language. In other cases, the mute half adapted over time by learning better language skills.  

Brain size

Although it is difficult to learn much from dissecting a brain, a lot can be learned by comparing the size and structure of the brains of different animals.

Animals with large bodies have proportionally larger brains. This suggests that much of the brain is dedicated to interpreting the body’s senses and controlling its muscle movements.

Mammals and birds have larger brains in proportion to their body size than fish or reptiles. Apes and monkeys have even larger brains, and humans have the proportionally largest brains of all, although our actual brain size is still smaller than that of whales and elephants.

By studying the fossilized skulls of our early ancestors, we can see that around 1.5 million years ago, the human brain took an evolutionary leap forward and began to increase in size. This corresponds with archeological evidence of increased tool use and improved tool design.


Brain structure

The brains of most animals appear to be similar in structure. All of the nerves from the body feed into the brain stem. On top of the brain stem is the hippocampus, which controls the timing of sleep, the heartbeat, and all other involuntary functions. Every multi-celled animal has a brain stem and a hippocampus, indicating that these were the first structures to evolve. They form a part of the brain called the ‘paleocortex’.

Mammal brains are unique in that they have an additional layer not found in other animals. This extra layer, called the ‘neocortex’, surrounds the paleocortex. This extra layer is believed to help override biological behavior with learned behavior, and at least in the case of humans, instinctual reactions can be overridden with calculated actions.

As the brain size of different mammals increases, the neocortex does not become thicker but instead increases in surface area. The surface area of a monkey’s neocortex is hundreds of times greater than that of a mouse, and the surface area of a human neocortex is hundreds of times greater than that of a monkey. This increase in surface area is achieved by folding the neocortex, which gives the human brain its distinctive convoluted appearance.  

Brain damage

Another obvious area of research has been to study the effects of brain damage. Damage to specific areas of the brain can have an effect on specific functions and abilities.

For example, damage to areas at the back of the brain can affect eyesight, and damage to areas on the side of the brain can affect hearing. From this it might be assumed that specific areas of the brain have evolved to perform specific functions. However, this is not necessarily the case.

Researchers have discovered that when brain tissue is removed from a healthy part of the brain and used to replace damaged tissue, the transplanted tissue learns to function like the lost tissue.

It has also been observed that if damage to the brain occurs early in life, other parts of the brain can adapt and take over some of the lost functionality. In fact, there have been cases where massive reorganizations of brain structure have occurred.

This indicates that all brain tissue is more or less the same, and that different regions of the brain only perform different functions because of their location. It suggests that whichever brain cells are nearest to a particular nerve path entering the brain from a particular part of the body are the most likely to learn how to adapt to that particular bodily stimulation.  

Brain scans

Another promising area of research is to use magnetic resonance imaging (MRI) to scan electrical activity inside the brain. Brain scans can highlight which areas of the brain are most active during certain thoughts and feelings. Although brain scans have become an invaluable research tool, they still provide only a fuzzy image at best.  

Nerve cells

Other researchers have been studying individual nerve cells in an effort to discover how they work, and how they work together. A highly complex biological process is being discovered. As we think, feel, learn, and make decisions, synaptic connections are made and broken, electrical fields are disrupted and reorganized, and concentrations of ions build up and diffuse away.  

Twin studies

One of the more unique opportunities that nature has fortuitously provided us with has been to study the psychological differences between identical twins, especially identical twins that were separated at birth and raised under different conditions.

Identical twins have identical brains, and so any differences in their psychology can shed light on which mental attributes are determined by a person’s genetic makeup and which ones develop through life experience.

After decades of studying identical twins, researchers have concluded that behavioral traits like creativity, extroversion, and aggressiveness are between 45% to 75% genetic, and intelligence may be as much as 80% genetic.

In other words, our mental potential and limitations are mostly inherited from our parents. But how we use our potential and how we overcome our limitations is still largely governed by experience and learning.  

Political correctness

Some scientists argue that trying to divide human behavior into a genetic component and a learned component creates an artificial distinction.

They argue that speculations about the genetic differences between people’s mental abilities can fuel socially destructive political ideologies.

Instead they prefer to describe every human mind as a blank page onto which the experiences of life are written, and upon which the personality develops almost entirely through experience.

They prefer this model because it infers that the differences between races, sexes, and classes are due to differences in opportunities rather than differences in inherited abilities.

When faced with the suggestion that human nature is genetically predetermined, they emphasize the enormous diversity of social and psychological phenomena found in cultures around the world and throughout history.

However, by ignoring biological realities in favor of an idealistic oversimplification of human nature, these scientists are often accused of placing politics ahead of science.  

Evolutionary psychology

Charles Darwin was the first scientist to point out that our common responses to certain emotionally charged situations, like our hair standing on end when we are frightened, are responses that probably evolved hundreds of millions of years ago in our early animal ancestors.

This led Darwin to question whether facial expressions like smiling and frowning are instinctual or whether they are cultural responses that we learn after we are born. Unfortunately, Darwin was not able to collect enough evidence to reach a conclusion.

It was not until the 1970s that enough evidence had accumulated for psychologists to confidently conclude that emotions like happiness, sadness, fear, and anger will always trigger the same facial expressions in every person, regardless of their cultural conditioning. Not only do they trigger the same facial expressions but also the same tone of voice and posture.

Generally speaking, some emotions trigger involuntary movements, and these instinctual responses are biological traits that evolved in our ancestors. However, many of these instinctual responses can be largely overridden by learned rules that dictate the appropriate ways for people to express their emotions in a particular culture.

Humans have evolved the capacity to learn the rules of our local culture. We seem to pick up these rules in the same way that we learn a language. We are not born with a natural affinity towards any particular language, but we have a highly refined ability to learn how to recognize and express whatever sounds satisfy our communication needs.  


The field of sociobiology began to emerge in the 1970s in the hope of identifying those aspects of animal and human behavior that evolved in our ancestors and can be proven to be biological and inherited.

For example, many species of animal, including humans, develop strong emotional attachments that drive them to be highly protective of their offspring. Sociobiologists reason that this protective behavior probably evolved because it helped those individuals who had the characteristic to survive and reproduce. Those that did not exhibit such protective behavior would likely lose their offspring and ultimately die out. Other social behaviors are said to have evolved in a similar way.

Unfortunately, because of the obvious temptation to talk about the evolutionary differences between races, sexes, and classes, some people accuse sociobiology of being a politically incorrect science. But sociobiologists are generally only interested in biological traits that evolved long before our last common ancestor - traits that affect the psychological makeup of every human being in more or less the same inherited way.

It is widely understood that biological behavior would take millions of years to evolve. It can be assumed that most human biological behavior was shaped by natural selection to solve the kinds of problems that were faced by our hunter-gatherer ancestors. It is generally agreed that there has not been enough time for our biological behavior to have evolved much since the Stone Age.

One serious problem with sociobiology is that although evolved patterns of behavior are easy to observe in animals, especially insects, they are very difficult to observe in humans. It is almost impossible to conclusively prove that any kind of human behavior is biological, because human behavior is so diverse.

Another serious problem is that because we cannot easily gaze into our evolutionary history, there is a tendency among second-rate researchers to rely more on speculation than on evidence. When unprovable speculations start taking the place of strictly objective experimental science, then sociobiological thinking can easily start to drift away from scientific thinking in ways that lead to objectionable conclusions.

The claims that are currently being made by a large number of “psychobiological extremists” have already been stretched far beyond what any evidence can support.  

Psychobiological extremism

Some scientists believe that different parts of the brain have evolved to become highly specialized at performing certain functions like detecting visible objects, controlling eye movements, recognizing faces, understanding sentences, memorizing information, making decisions, and a multitude of other specialized tasks.

Many of these scientists believe that our brains contain hundreds or even thousands of functionally distinct “mental organs”. They believe that for almost everything we do, there is a part of our brain that has evolved to become especially good at doing it, and all of the parts work together in such a way as to allow us to think and act the way we do.

Some of these scientists even believe that the functioning of our mental organs plays a major role in shaping and constraining our beliefs, preferences, emotional reactions, sexual behavior, and interpersonal relationships.

However, this way of thinking is also widely condemned as “psychobiological extremism”, because once you start attributing common behaviors to brain biology without having indisputable evidence to support your claims, it is not long before you start to blame every type of human behavior on some as-yet-undiscovered “mental organ of convenience”.

Some extremists have even gone so far as to suggest that there is a mental organ responsible for religious belief, the so-called ‘god module’, the instructions for which are genetically encoded in our ‘god gene’. Such ideas are easily discreditable because they try to oversimplify social phenomena that are so complex that they seem to be almost impossible for the average person to comprehend.

These kinds of unsubstantiable speculations have become so pervasive, because of their sensationalist potential, that even otherwise reputable scientific publications cannot help themselves but to cash in on the controversy by printing articles about every nutcase behavioral gene theory that crawls out of the academic trashcan.

Not only is there no evidence for almost any of these claims, the circumstantial evidence weighs heavily against them. For example, the development of functionally specific mental organs would be an evolutionary dead-end. The evolution of animal faces might have slowed down to a halt if corresponding changes were also needed in a specialized face recognition brain module.

One of the primary functions of the brain is to recognize things. So why would any part of the brain evolve to become specialized at recognizing faces or spoken words or any other thing, when a much more effective result could have been achieved through the evolution of a generalized ‘everything recognition’ ability? There is no reason why the pathways that recognize faces could not also be used to recognize the words on this page. For a literate person, reading seems natural, but writing is a relatively new invention, so we clearly did not evolve any special ability to recognize written words.

Another primary function of the brain is to control our actions. There is not much functional difference between throwing a ball and swinging a hammer, and in a similar way, there is no reason to believe that the same generalized ability could not be used to sing a song, whistle a tune, or play a gazoo. There would rarely, if ever, be any need for specialized brain functionality.

One of the most convincing evidential arguments against psychobiological extremism is that there are simply not enough genes in the human genome to account for all of the commonly observed patterns of behavior. Even if there were tens of thousands of genes in the human genome, these could not code for the trillions of synaptic connections in our brains.

There is no doubt that evolutionary forces directed human brain development, but increased generalization leading to increased flexibility and adaptability would have been much more useful and evolutionarily successful than increased specialization, and it would better explain the effortlessness with which humans have migrated from the jungles of Africa to the concrete jungles of modern suburbia.  

Cognitive psychology

As computers became more common in the 1950s and 60s, some researchers began to emphasize the similarities between brains and computers. Perceiving the human brain to be a powerful organic computer, they began to describe mental processes in the same way that computer scientists were describing artificial intelligence. This approach became known as ‘cognitive psychology’.

While some psychobiological extremists also like to describe the human brain as an organic computer, comparing functionally specific mental organs to individual circuits, this is actually a bad analogy, because in the evolution of the electronic computer, dedicated circuits have given way to a single processor which performs relatively few functions. Processors only need to be able to store and retrieve information, and compare and combine information. With these few functions, they can be programmed to do almost anything.

As far as computer analogies are concerned, respectable cognitive psychologists say that the human brain operates like a massively parallel computer, which is continually trying to comprehend our situation by comparing our current perceptions to memories of similar or related experiences in the past. We then respond in whatever way we have learned to. If we have no previous experience then we simply learn from our mistakes.

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