Neural connections are shaped by life experiences
The brain changes continually as a result of our experiences. Experiences produce physical changes in the brain either through new neural connections or through the generation of new neurons. Studies suggest that the brain can change even during the course of a day. This means that the anatomy of the brain varies from individual to individual. Even identical twins with identical genes don't have identical brains. They have had different life experiences.
Experiences are the reason that all individuals are unique. There are no individuals with exactly the same upbringing, nutrition, education, social stamping, physical, social and cultural setting. This creates different convictions, habits, values and character. People behave differently because differences in their environment cause different life experiences. This is why it is sometimes hard to understand other people's behavior. To do that, we must adapt to their environment and share their experiences. This is often impossible.
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If we encounter a stressful situation, how we respond depends on what we were born with, what we have experienced, and the specific situation. Assume that a person "Sam" and you both have genes for "being fearful." You are standing in a Savannah in Africa and are approached by a lion. Do both of you show the same reaction when exposed to the same situation? You are afraid but not Sam. Sam either knows that this lion is tame or Sam is a lion tamer. Sam's reaction comes from his life experiences. Sam may also be genetically predisposed to react differently to certain dangers. But even if Sam has a low genetic vulnerability to fear, he can develop a fear of the lion. One horrifying experience with a lion may be enough.
Behavior is influenced by our state of mind
Our life is what our thoughts make it.
Marcus Aurelius Antoninus (Roman emperor and philosopher, 121-180)
Our state of mind is a function of our life experiences and the specific situation. Assume (1) we are eating tasty chocolate, listening to wonderful music and feeling relaxed or (2) we suffer from a cold, feel stressed and just ate a bad meal. If we have to make a judgment, will it be the same in both cases? Probably not, since our state of mind is different in case 1 and 2.
Can our state of mind influence our biochemistry and immune system?
It's not just what happens to us that counts - it's what we think happens to us. We convert our expectations to a biochemical reality meaning that our mental state and physical well-being are connected.
A placebo effect is a positive therapeutic effect that has nothing to do with the efficiency of a treatment, only with a patient's belief in the treatment. Whenever patients believe that a treatment will have a particular physiological, behavioral, or psychological effect, they are susceptible to placebo effects.
The doctor gave me a pain-relief drug (when in fact it was a sugar pill) and after a short time I experienced significantly less pain.
A placebo is an inactive or ineffective treatment or substance (for example, sugar pills or injections with saline solution) that is often used in comparison with active treatments. Studies show that a placebo can improve a patient's condition simply because the patient expects it will work. Clinical evidence shows placebos to have physical effects on the brain, just as drugs do. Studies in Sweden show that a placebo activates the same brain circuits as painkilling drugs. Nine male
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students were asked to voluntary participate in a study of painkilling drugs. Researchers first tested for the degree of pain the subjects would experience when a 48-degree Celsius metal surface was pressed to the backs of their hands. The test was repeated after the subjects were given a painkilling drug.
Later the subjects were told to test two new painkilling drugs and that one of these drugs was similar to the one they earlier tested. Once more the 48-degree metal surface was pressed to the backs of their hands. A man in a white coat, carrying a badge that said "professor", then entered the room. The "professor" gave the subjects intravenous injections of either an opioid (a drug acting like a drug made from opium) painkiller or a placebo. During the experiment researchers scanned the subjects' brains and compared brain responses. Both the painkiller and the placebo produced the same effect. Both increased blood flow in areas of the brain known to be rich in opioid receptors. Eight of the nine subjects said that the placebo produced a clear relief from the pain.
Other studies show that people who take sugar pills as a treatment for depression and other ills can undergo striking, although temporary, changes in brain activity and neural chemistry as their condition improves. It has also been shown that placebos can improve blood pressure, cholesterol level and heart rate. It's like a pharmacy inside the body that has evolved during million of years of evolutionary time.
What happens when a healthy person finds out he may die?
Studies show that if people expect something to go wrong with their health, it often does. Negative expectations can influence our bodies and cause symptoms that over time may cause our body harm. In one study, women who expected that they were inclined to heart attack were nearly four times as likely to die as women with similar risk factors but without these expectations. Another study found that patients who were warned about the gastrointestinal side effects of taking aspirin were three times more likely to feel them. Other studies show that if people worry about drug side effects, they are more likely to get them. Beliefs have biological consequences - good and bad.
Our genes and life experiences determine how neurons connect thereby influencing and setting the limits for our behavior. We were born with the basics of life. We had neural connections that regulated our breathing, heartbeat, temperature, etc. How does our brain select those neural connections that produce useful behavior? Our brain is a product of evolution.
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- Two -
EVOLUTION SELECTED THE CONNECTIONS THAT PRODUCE USEFUL BEHAVIOR FOR SURVIVAL AND REPRODUCTION
What do we mean by evolution?
Evolution is change (structural, physiological, behavioral) - which occurs over time through interaction with the environment. Paleontology Professor John Horner says in Dinosaur Lives: "When you flip through the pages of the family album you're witnessing evolution at work."
The theory behind evolution is that all individuals alive today have evolved from simpler, more primitive forms oflife. Since every living thing uses the same genetic code, it is likely that life descended from a distant common ancestor that had that code. If a monkey and we and any other organism trace our ancestors back far enough, we eventually find a common ancestor.
What major mechanisms are responsible for evolution and for how our brain evolved? Mutation and natural selection.
Mutations cause variations
Mutations are caused by a copying error in the sequence of A, C, G and T molecules when DNA is copied. This error in the genes "spelling" may cause a change in a protein leading to a modification in the individual that inherits the gene. For example, the new instruction could be"build Peter with adifferent eye-color." Since the change is random and unpredictable, no one can tell which gene(s) may be involved.
Natural selection
I have called this principle, by which each slight variation,
if usefol, is preserved, by the term Natural Selection.
Charles Darwin (British naturalist, 1809-1882)
Charles Darwin, and independently the British naturalist Alfred Russell Wallace, discovered the theory of evolution by natural selection. Darwin called his work On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life.
Darwin was inspired by the Reverend Thomas Malthus's An Essay on the
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Principle of Population in which Malthus wrote: "Human population grows exponentially, like compound interest in a bank account, but farm output rises at a slower, arithmetic rate; the result, human population will inevitably and repeatedly outstrip its food supply." Malthus noted th
at population can always outstrip resources but are held in check by diseases, war, predators, and by limited resources like food.
Darwin made the following three observations:
(I) Competition and environmental change. In most species (a species is a group of individuals capable of producing fertile offspring; like snakes, lion, humans) there are always more offspring born than can survive to adulthood and reproduce. Darwin saw two reasons for this: (1) Since there is a limited amount of resources (like food, space, mates) there is competition between individuals for these resources, and (2) Since the environment changes over time and from one region to another, there are threats (predators, change in climate, isolation, diseases, change in the physical environment) to the children's survival and their reproductive success.
Individual variability. Within a species, there is an enormous amount of
individual variation. No two individuals of the same species are alike in their anatomical structure, physiology or behavior (we're not an exact copy of our parents). Individuals vary in their cell structure, fighting ability, and social skills. Variations make every individual unique and that variation must in some way be heritable otherwise children wouldn't resemble their parents more than they resemble other individuals.
The world is not fixed but evolving. Species change, new ones arrive and
others go extinct.
Darwin called his principle natural selection. Any slight variation in traits that gives an individual an advantage in competing with other individuals of the same or different species or in adapting to changes in their environment increases the chance that the individual will survive, reproduce, and pass along its characteristics to the next generation. Maybe they have greater resistance to disease, or can run faster, or survive climate changes better.
Darwin used the word "selection," but nature doesn't care who gets selected for survival. Evolution has no goal. Another way to describe natural selection is as a process of elimination. Certain individuals survive because they have structural, physiological, behavioral or other characteristics that prevent them from being eliminated. Those that don't have these characteristics are eliminated. Heredity enhances the likelihood that the non-eliminated or "selected" variations
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are preserved. Darwin didn't know about genetics. Therefore he couldn't know that these characteristics were caused by mutations and that they could be passed on through the genes.
After a mutation changes an individual, the environment determines if the change gives the individual an advantage. If the new trait is helpful, the mutated individual is more likely to survive, reproduce and pass the new trait to his children. Take a poisonous spider as an example. Assume that a population (a group of individuals belonging to one species that occupy the same geographic/ecological niche at the same time) of black widows differs in how toxic their venom is. If some spiders (mutants) are born with more toxins than others, two things could happen over time. If more toxins give an advantage in the spiders' environment, more toxins might be "selected" for and the "more-toxins" characteristic might be passed to children. If the more toxic black widow spiders survive and reproduce better than the less toxic ones, then black widow spiders, will, over time, evolve more toxic venom. The frequency of the "more-toxic" spiders in the population increases over time. If there is no advantage, the trait disappears and
the population of less toxic spiders increases.
When organisms undergo selection, some characteristic may be carried along that wasn't selected. Even if some trait didn't provide an advantage it could still be carried along as long as it isn't harmful, i.e., doesn't negatively influence survival and reproduction. But a situation may arise in the future when that trait can become useful.
What happens when the environment changes?
Since environments change over time and with geography, different variants are "selected" under different conditions. Characteristics that are successful in one environment may be unsuccessful in another. This is well expressed by the late American paleontologist Stephen Jay Gould in Wonderful Life: "Even if fishes hone their adaptations to peaks of aquatic perfection, they will all die if the ponds dry up."
Studies show that different organisms respond differently to environmental stress. But there seems to be one creature that survives and reproduces independent of changes and stresses in the environment - the cockroach. Writer Richard Schweid says in The Cockroach Papers, "If there is a God that made all life forms, a particularly rich blessing was bestowed on the roach, because it got the best design of all."
The cockroach is the oldest insect on our planet as evidenced by fossil records dating back 325 million years. It can eat almost anything, live 45 days without
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food, and has an effective reproductive system with female sperm storing capabilities lasting a lifetime and a great defense system. The cockroach is about the same organism it was millions of years ago because its characteristics were adaptive then and now.
Often a new trait or a change in an individual doesn't occur through a single step but through a gradual accumulation of small mutations being selected over a long period of time. By dating meteorites, most scientists say that the earth is about 4.6 billion years old. The oldest bacteria fossils go back 3.5 billion years. Given enough variation and time, even such a complicated thing as the eye hasgradually developed. Evolutionary changes can act fast. Studies of fruit flies show that differences in wing size could take place in as little time as adecade. A change in a species' territory (e.g. climatic) can also bring on rapid structural changes (variation). Other studies show that a change that involves few genes could come about faster (and cause large
behavioral changes) than one that depends on small changes in many genes.
Mutation is not the only source of genetic variation. Other mechanisms (sometimes interacting) are genetic drift, gene flow, and symbiosis. Genetic drift happens when random events cause gene frequencies to vary between generations (more important in small populations). Gene flow or migration is the movement of genes in a species from one population to another as the result of interbreeding. For example, there is evidence of gene flow between cultivated plants and their wild relatives. Symbiosis is the cooperative interaction between different organisms that can produce genetic changes. There is also co-evolution or the parallel evolution of two species. Another source of variation is gene duplication or the accidental duplication of entire genes. So natural selection is not the only mechanism that changes organisms over time. But it is the only known process that seems to adapt organisms over time.
The evidence for evolution
There is fossil, anatomical and molecular evidence of evolution. The fossil record shows how morphology was modified. Similarities of organs in related organisms show common ancestry. There is also DNA fossils evidence where human relative relatedness can be measured by DNA sequencing.
One example of evolution is industrial melanism. Before the Industrial Revolution in England, the color of the peppered moth was mainly light. When there was no industrial pollution, the darker moth cropped up by mutation. But since the darker moths were easier to spot against the tree bark, hungry birds snapped them up. Only when the environment changed, when soot from new factories covered the tree trunks, did darkness became an advantage. Selection
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began to favor the darker moth. Darker moths were better disguised on tree trunks covered by soot. The lighter moths were eaten and the darker ones increased in numbers. Around 1950 the environment started changing again. A decrease in the use of coal and better filtering equipment in the factories produced a cleaner environment and the peppered moth is in the process of returning to its lighter color.
Why aren't antibiotics as effective against dangerous bacteria as before?
Evolution is at work today. Evidence of evolution is seen in pesticide resistance among insects and the antibiotic resistance of bacteria.
There are a lot of b
acteria around, and they can divide several times an hour. In any population of bacteria, there are some individuals that through mutations have developed genes causing them to escape elimination. The more non resistant bacteria that are eliminated, the more opportunities for the resistant to reproduce and spread. Over time, the resistant bugs win the race, meaning the antibiotics become less and less effective. Until someone develops a new type of antibiotic and then the race starts all over again.
Bacteria are immensely adaptable. Expose them to antibiotics long enough, they adapt and find a way to survive. This also means that the more we use antibiotics, the faster resistance spreads. And any method we use to kill bugs will, unless it completely wipes out a species, cause a population of resistant bugs.
Just as we can't blame an animal for eating another animal to survive, we can't blame bacteria for giving us an infection. They have no intention of harming us. Bacteria do what comes natural to all of us - survive and reproduce.
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