“Nothing in Biology Makes Sense Except in the Light of Evolution”
– Theodosius Dobzhansky (1900-1975)
Ukrainian-American Geneticist and Evolutionary Biologist
Most humans older than 60 years of age have a detailed memory of the Vietnam War. The Vietnam War extended 20 years, from 1955 to 1975.
United States soldier-on-the-ground involvement in the war extended primarily from 1965 to 1975. The collective consciousness of America was largely fixated on the war. It had a profound influence on the American society and the world. For many, the influence is still profound (2022).
The peak year for US soldier deaths in Vietnam was 1968 with 16,899 (1). That same year (1968), Stanford University biology professor Paul Ehrlich, PhD, wrote a book that may have received more publicity had it not been released at the height of the Vietnam War. In his book The Population Bomb, Dr. Ehrlich notes that planet earth could only produce enough food to feed about 4 billion people, which was the approximate population of our planet in 1968. Dr. Ehrlich (and his wife Anne Ehrlich, uncredited) predicted that humans were on the cusp of mass starvation and worldwide famine.
When Dr. Ehrlich wrote his book, he did not know that there was already a person on the problem. Norman Borlaug, PhD, (d. 2009, age 95), was an American microbiologist from the University of Minnesota. In 1968 he was in Mexico, genetically manipulating wheat, drastically increasing per acre crop yields (3, 4, 5).
This year, 2022, human death rates are often constant headline news stories. Infection, war, murder, suicide, overdoses, disasters, disease (heart disease, cancer, etc.), accidents and more. Yet, this year, the population of planet earth will surpass 8 billion people, twice as many people as Dr. Ehrlich predicted our planet could feed.
Ironically, in 2016, the journal Lancet published a study looking at adult body-mass index in 200 countries from 1975 to 2014 (6). The study had 756 global collaborators and it involved more than 19 million participants. Shockingly, per capita, every country became heavier.
Dr. Ehrlich is now 90 years of age. Dr. Borlaug (d. 2009) was awarded the 1970 Nobel Prize for his genetic work on wheat. It is often noted that Dr. Borlaug prevented more human starvation and suffering (literally billions of people) than any person in history.
Our genetic material passes parental traits to their offspring during conception (7, 8). Our genetic material exists in strands of 23 pairs of molecules called chromosomes. Any one strand is made up of molecules called deoxyribonucleic acid, or DNA. The information used to create proteins exists in DNA. This information is our genetic code.
Plants, animals, most microbes, etc., share the “letters” of the genetic code. In essence, there are only 4 letters: A, Adenine; C, Cytosine; G, Guanine; t, Thymine.
Each letter is known as a nucleotide base. In total, the human genome is comprised of about 3 billion nucleotide bases (3,117,275,501 is the exact number, reference #9).
Proteins are made from 20 different molecules called amino acids.
Three adjacent nucleotide bases are called a codon. A codon is associated with one amino acid.
The assembled sequence of amino acids creates a protein. Some proteins are made from a smaller number of amino acids: insulin is 51 amino acids long. Other proteins are much longer: collagen is about 1,000 amino acids long (the structural protein in skin, tendons, ligaments, cartilage, etc.). [see graphic on following page]
The section of DNA containing the nucleotide bases that code for a single protein is called a gene. Human DNA contains about 20,000 genes.
Feeding the World Background
In the mid-1800s (about 1840-1874), an unexpected global powerhouse was the country of Peru (and to a lesser extent, contested, Chile). It had been understood that the rate-limiting ingredient in growing food was the availability of nitrogen. Nitrogen is the primary ingredient in guano (poop from birds, bats, etc.). Islands off the west coast of Peru, owned by Peru (contested, especially with Chile), had been accumulating guano for millennia, often reaching heights of hundreds of feet. Ships from around the globe would travel to these islands, often waiting for months, to load their hulls with guano to grow food in their nations.
By about 1874, guano reserves had been depleted. Suddenly, humans, who had transitioned largely from hunter-gathers to farmers for their food supplies, were in trouble. By the turn of the century (1900), experts estimated that global food production could only feed about 1.5 billion persons, and the approximate human population was about 1.5 billion persons.
A German chemist, Fritz Haber, PhD, went to work to solve and prevent what could become a catastrophic problem: wide-spread global human starvation. Haber was aware that about 70% of air is nitrogen, but accessing that nitrogen seemed impossible because of the nitrogen-nitrogen triple bond. Haber overcame that obstacle with extreme pressure (compression) and high heat in the presence of hydrogen. The results were an ammonia-based nitrogen fertilizer that was used to grow crops (10). Suddenly, earth could feed 4 billion people.
Dr. Haber’s discovery was credited in 1909, and he was awarded the 1918 Nobel Prize in chemistry. Yet, his contributions are tainted because Haber’s work had a darker side:
- Haber discovered that his ammonia-based nitrogen fertilizers were highly explosive. His technology and facilities were used to make the bombs of World War I (1914-1918) and beyond through today, killing millions.
- Haber also created the horrific toxic gasses used to kill solders in the trenches of World War I. In their first application, about 6,000 soldiers died. Overall, about 100,000 soldiers were killed, and about a million were permanently disabled.
- Production of ammonia-based nitrogen fertilizers emits more global-warming carbon dioxide than any other chemical-making process (10).
- Water pollution from ammonia-based nitrogen fertilizers creates oxygen-depleted dead zones which further significantly contribute to global warming. (10).
Learning and understanding evolutionary biology is a fascinating scientific endeavor (11). Species, including humans, adapt to environmental changes, or they become extinct. Adaptations occur slowly over many (thousands) generations and thousands of years. Environmental changes that occur too quickly can have huge negative impacts on human health.
Without the rapid innovations of Drs. Haber and Borlaug, planet earth would be a much different place. Dr. Haber’s rapid environmental change was based on chemistry. Dr. Borlaug’s accomplishments were based upon genetic manipulation. Today, rapid environmental changes are often a combination of both chemistry and genetics. For example, crops (corn, soy, wheat, etc.) are genetically altered to withstand the toxic effects of the chemical herbicide glyphosate (12).
Initially, the innovations of Drs. Haber and Borlaug were viewed only as positive. Yet, history is suggesting that such rapid changes may have had negative consequences (12, 13).
The point of this is to briefly discuss evolutionary biology. One such way in which humans have adapted evolutionarily is their perception of pain, especially of post-traumatic whiplash injury pain.
Overwhelmingly (93%) of the public seeks chiropractic care for the management of spinal pain syndromes (14). Sixty-three percent of patients go to chiropractors for the management of back pain and 30% for neck pain.
Whiplash injury primarily causes neck pain (15, 16, 17, 18). Chiropractic care is very successful at treating neck pain (19, 20, 21) and specifically whiplash injury neck pain (22, 23, 24).
Whiplash injuries are not only a health problem. Whiplash injuries often involve the carelessness or negligence of another party/person. This means that whiplash injuries are also legal problems.
An expert is a person who has obtained a high level of knowledge on a specific topic by virtue of their education, training, and/or experience. The chiropractor treating whiplash-injured patients is considered by all parties (patients, attorneys, insurance providers, etc.) to be an expert. All parties to the whiplash injury rely on the opinions of the treating chiropractor to explain the particulars of a specific patient’s condition. This includes topics such as injury mechanism, causation, clinical symptoms, examination and imaging findings, treatment recommendations, prognosis, work/leisure restrictions, long-term and/or permanent impairments, complicating factors unique to an individual and/or injurious event, and much more. Treating chiropractors who may not have a full understanding of expert issues may harm the legal component of a case.
A common expert obstacle pertaining to the acute whiplash injury is the delay of symptomology. The delay of symptomology for those involved in motor vehicle collisions is more the rule than the exception. The parties involved in the crash often have no symptoms at the accident scene. Individuals initially believe that they are uninjured and so inform other parties at the accident scene. If police officers arrive and make a police report, the parties involved often report to the officers that they are not injured and the report will record that sentiment.
Although subjectively asymptomatic for pain, crash scene subjects are often slightly dazed and confused. Many report that the loudness of the crash startled them. They are exchanging personal and insurance information. Their hearts are racing and their blood pressure is elevated. They are confused and angered. They are concerned about being blamed for the collision or assigning blame to others. Their minds are preoccupied with concern over the welfare of others involved who may be injured, including passengers in their own vehicle, which often included family members or perhaps children. Everything becomes a worry, including work, school, shopping, doctors, fixing the vehicle, etc.
All of these events have triggered the classic flight-or-fight response. The flight-or-fight response was first described by Harvard Medical School physician and physiologist Walter Cannon, MD, in 1915 (25) (d. 1945, age 73). As with everything in evolutionary biology, the flight-or-fight response is a genetic neuro-hormonal response that improves the survival of the individual and hence the survival of the human species. Individuals with a robust flight-or-fight response survive frightening and/or dangerous situations, and they pass those genetic characteristics to their offspring. Individuals with a lesser flight-or-fight response do not survive. This means that humans today genetically retain a robust flight-or-fight response.
An interesting and important aspect of the flight-or-fight response is that once it is triggered, the individual will ignore or be unaware of injury and/or pain. Through the genetics of evolutionary biology, the ability to ignore injury and pain would give an individual a selective advantage for survival. In the Paleolithic era, if injured or wounded in a fight or hunt or during an escape, suppression of pain would enhance survival. The technical terminology for this phenomenon is Stress-Induced Analgesia.
Often, whiplash-injured patients will not complain of pain until the day following injury, and sometimes pain will be delayed for several days or longer. This delay in symptom expression is often used to argue a variety of points:
- The patient was not injured.
- Patient injuries were, at most, minor, or the patient would have expressed immediate symptoms.
- The patient has become aware that they may be eligible for some sort of financial compensation. The motive for obtaining this financial compensation is referred to as secondary gain. Quite often, such financial compensation requires health care provider documentation for symptoms. An argument is made that the patient now seeks health care provider assessment in order to secure secondary gain.
- The patient is faking or embellishing symptoms (malingering) for other motives, such as sympathy, time off, justification of reduced work-loads or family obligations, etc.
A very common explanation for delayed symptoms following whiplash injury uses these points:
- Pain occurs as a consequence of an accumulation of inflammatory chemicals.
- Injury produces and releases pain producing inflammatory chemicals.
- The pain producing inflammatory chemicals must reach a set quantity in order to cause the pain neuron action potential.
- The accumulation of these pain producing inflammatory chemicals increases over hours or days until excitation threshold is achieved, accounting for symptom delay.
Although this explanation may have some validity, the stress-induced analgesia model is increasingly being accepted (26, 27). In 2009, the journal Progress in Neurobiology published a study titled (26):
The authors, from the National University of Ireland, produced the most detailed review of the literature on the topic, citing 350 references. The authors review the neuroanatomy, neurophysiology, and both the animal and human experimental basis for stress-induced analgesia.
The authors note that pain is an evolutionarily defense response to an aversive or noxious stimulus. They define stress-induced analgesia as a pain suppression response that occurs during or following exposure to a stressful or fearful stimulus. The authors make these important points:
“For over 30 years, scientists have been investigating the phenomenon of pain suppression upon exposure to stressful stimuli, commonly known as stress-induced analgesia.”
“Stress-induced analgesia is influenced by age, gender, and prior experience to stressful, painful, or other environmental stimuli.”
“From an evolutionary perspective, stress-induced analgesia may be thought of as a component of the ﬁght or ﬂight response.”
“Tending to a painful injury would not be conducive to the survival of an organism if further injury or death were threatened.”
“Once the organism is no longer in danger, however, elevated nociception, expressed upon extinction of the aversive response, could be beneﬁcial as normal behaviors may aggravate the injury.”
“Predator–prey interactions most likely played a major role in the evolutionary development of stress-induced analgesia.”
“Predator preference for injured prey, based on maximizing energy expenditure to consumption efﬁciency, may have led to a selective pressure for the evolution of animals which express stress-induced analgesia in threatening situations.”
The authors conclude that from an evolutionary perspective, the induction of fear, concern, worry, confusion, noise, stress, etc., decreases the sensitivity to pain. As the neuro-endocrine basis for these emotions decrease, pain is perceived.
Stress-induced analgesia is discussed in detail in the 2022 book titled (27):
The Brain and Pain:
Breakthroughs in Neuroscience
The author, Richard Ambron, PhD, is emeritus professor of pathology, anatomy, and cell biology at Columbia University. Dr. Ambron makes these comments:
“… you are walking in the woods and twist your ankle. You sit down on a log in considerable pain, but if a bear were to suddenly appear, you would get up and run as if you weren’t in pain. … you are experiencing what is known as stress-induced analgesia, i.e., a painful injury that would be incapacitating under normal circumstances can be ignored in order to escape death.”
“Stress-induced analgesia was a well-documented phenomenon during World War I, when soldiers with grievous wounds disregarded their pain in order to escape danger. … it was clear from the experiences of the soldiers that pain is not an automatic response to an injury.”
“…stress-induced analgesia was predicated on the idea that the body has an internal mechanism for dealing with pain.”
Dr. Ambron’s explanation for the mechanism behind stress-induced analgesia is that stress neurologically activates the descending pain inhibitory control system. Importantly, there is compelling evidence that chiropractic spinal adjustments are effective in reducing pain because manipulation also activates the descending pain inhibitory control system (28, 29).
Stress-induced analgesia is a neurological phenomenon. Its existence is independent of the degree of actual tissue injury. Additional support for whiplash injury pain (or pain suppression) as being primarily a neurological phenomenon appeared in the journal Frontiers in Neurology, in 2022. The study was titled (30):
The Whiplash Disease Reconsidered
The authors are from the Department of Neurology, University of Copenhagen, Denmark. The authors emphasize the common delay in injury symptomology following motor vehicle collisions and argue that this delay is best explained neurologically rather than by tissue injury. These authors suggest an evolving neurological mismatch disorder is an explanation for whiplash injury pain. They state:
“It is assumed that a whiplash-type trauma is causing an acute tissue injury such as a distortion or sprain in the neck followed by neck pain and headache, which then tends to become a chronic pain condition.”
“This tissue injury is supposed to be the cause of the acute symptoms, which then may be followed by secondary neuromodulation of the central nociceptive perception, causing a chronic condition of central hypersensitization resulting in lowered pain threshold and hyperalgesia.”
These authors suggest that whiplash injury initiates a dysfunction in the central nervous system. They present an argument and evidence that the causative pathology of chronic whiplash disorder is “a central nervous system disorder,” and not an ongoing musculoskeletal injury. They suggest that effective treatment for chronic whiplash is through interventions that alter nociceptive neurology as opposed to interventions that primarily target injured soft tissues.
The Bottom Line
Stress-induced analgesia is the genetic consequence of evolutionary biology. It represents an adaptation that increases an individual’s survivability in dire situations. Modern humans continue to exhibit this genetic trait of neurological pain suppression. Modern examples include battlefield injuries and whiplash injury, and countless other events.
Stress-induced analgesia is neurologically driven by the descending pain inhibitory control system. The descending pain inhibitory control system is also activated by chiropractic spinal adjustments (28, 29).
A model evolves that suggests that chronic whiplash pain persists because of a neurological mismatch in the operation of the descending pain inhibitory control system. Chiropractors assert that spinal adjusting helps correct this neurological mismatch, explaining why chiropractic care is often successful in treating chronic spinal pain complaints.
Additionally, chiropractic spinal adjusting has the unique ability to not only improve the descending pain inhibitory control system mismatch, but to also improve the timing and quality of the original soft tissue injury. This hypothesis is supported by Yale Medical School’s leading biomechanical expert Manohar Panjabi, PhD (31).
Conversational expertise on the topics, especially on the issue of delayed pain following whiplash injury, is very valuable in both patient education and for any med-legal inquiries.
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