Sticky film on our teeth is a perfect habitat for tooth decay bacteria
Combination of wheat, sugar, and milk is like a bacterial smorgasbord…
Abrasion of raw food (ancient diet) wears teeth down more quickly, but also scrapes off the bacterial buildup, prevents decay
Modern agriculture is the source of many of our chronic health problems
Consider that classic New World combo, corn and beans…
Corn (maize) and beans formed the staple diet of many New World cultures, still true today in many regions
Nutrionally sound, from the point of view of proteins
Need to get or make all of the 20 amino acids our bodies use to make proteins
Corn and beans between them have all 20 amino acids, in addition to carbohydrates and fats
Southern US natives switched to a corn/beans diet ~1,500 years ago
Made nutrition easier, with reliable crops, healthy protein diet
But not as healthy as the diet of their hunter-gatherer ancestors
Ancestral skeletons of southern natives are more heavy set, fewer nutritional problems evident in their bones
Corn and beans is great for proteins and carbohydrates, but lacks some essential vitamins and minerals
Milk is another nearly perfect food, with milk sugar (lactose), fats, and plenty of high-quality protein
Designed by evolution to nurture the young of mammals (Latin word “mamma” means breast)
Digestion of milk sugar (lactose) requires a special enzyme, protein called lactase
Lactase breaks lactose down into two simpler sugars which babies can digest
After weaning, the lactase gene is switched off in all mammals, body can no longer process milk sugar
Human babies are born able to digest lactose
Presumably, our ancestors were like other mammals, and lost that ability after weaning
Before the days of soy milk (~ 30 yrs. ago), babies who couldn’t digest mother’s milk were dead babies
Strong selective pressure for being able to digest milk sugar before weaning
No selective pressure to retain that ability after weaning (mother’s milk was the only source)
But many human races, unlike other mammals, remain lactose-tolerant after weaning
In lactose-intolerant people, milk sugar is not digested, provides rich food for tummy bacteria, get severe digestive problems
F.J. Simoons (1978) looked at 197 populations from around the world, and found a very interesting pattern
Lactose-tolerant populations were concentrated in particular ethnic groups
They were mainly northern and western European races, and their New World and Australian descendants
Included also were a few African, Mideastern tribes
Durham (1991) chose 60 populations to represent the full spectrum of human agriculture:
hunter-gatherers
crop farmers
dairy farmers
mixed dairy/non-dairy ancestry
Clearly shows the relationship between type of subsistence and lactose tolerance
Dairy tribes tend to be very lactose tolerant, hunter-gatherers and non-dairy tribes tend to be lactose-intolerant
African-Americans are mostly lactose-malabsorbers (= lactose intolerant)
Populations considered to be “lactose malabsorbers” are those where 70% or more have trouble digesting lactose
73% of African-Americans are lactose-malabsorbers to some degree, vs. 16% of the white population (Lockwood and Caldwell 1995)
African-Americans are mostly descended from tribes that did not raise cattle for milk
No one knows when dairy farming began
Maybe 5-8,000 years ago…
Did the regular availability of animal milk as food select for the ability to digest it after infancy?
Perhaps, perhaps not…
There is a widespread cultural solution to lactose-intolerance
Many dairy cultures use milk in the form of cheese and yogurt
Cheese and yogurt are OK for lactose-intolerant people
In the fermentation of milk, bacteria change lactose to lactic acid, or back into simpler sugars
Use of cheese and yogurt is widespread, but has not always selected for lactose intolerance
Some cheese/yogurt cultures are lactose intolerant, some are not
And the percentage of lactose tolerant dairy farmers, though logical, is high (over 90%)
Durham reasoned that these inconsistencies suggested a deeper pattern
There must be an additional source of evolutionary pressure selecting in favor of lactose tolerance
And therein lies a tangled tale…
Durham went back to his original study, this time looked at where lactose-tolerant groups lived
Found a strong correlation with latitude - lactose tolerant groups were more northern
Why did latitude correlate so strongly with lactose tolerance?
Before we can solve this puzzle, we must first consider another curious way in which cultural evolution has caused disease
It began hundreds of thousands of years ago, when we first migrated north, out of Africa…
Cultural evolution allowed our species to establish itself in parts of the world where more primitive man could not survive - high latitudes, high altitudes
These places are mostly cold and dark…
Ability to make fire, build shelters, skin animals, enabled us to move to higher latitudes
Many people today live in very cold climates…
Living in colder, darker climates has caused some interesting and unusual health problems
Arabs developed distillation in the 9th Century, could now get very high alcohol %
Ironically, one of the only group of people today who do not abuse alcohol are Arabs!
Before distillation, alcohol was probably limited to small batches of weak beverages, brewed at home
Distillation made the process much more efficient, even a small still could produce large amounts of potent brew
Natural tobacco is also harder to abuse
Raw leaf is very harsh, hard to smoke enough for addiction
Processed tobacco is smoother, allows much higher intake level
Same is true for many recreational drugs
Cocaine now refined into crack, opium into heroin etc…
Civilization has refined many natural drugs, suddenly making them much more powerful, easy to abuse
Drug use is usually seen as maladaptive
Many hypotheses have been proposed to suggest it might have evolutionary roots
If nothing else, considering the problem from an evolutionary viewpoint might suggest a solution
Moral perspective has not worked…
Problem once again is ready availability of substances that used to be relatively rare in our environment
The same applies to our consumption of excess dietary salt
Chronic high blood pressure is a major modern health problem
One of the primary contributing factors is excess dietary salt
Larger body size, stress, also contribute
Our average body size is larger than it used to be - blood pressure is adjusted to a lower range of body sizes
Brain not quite caught up with regulating blood pressure in larger bodies
Stress of modern life also adds to high blood pressure
High blood pressure is a common symptom of many chronic degenerative diseases (CDD’s)
CDD’s may be caused by multiple factors
May also be a genetic predisposition to CDD’s
It’s easy to dismiss CDD’s as part of the price for growing old - Alzheimer’s disease, heart disease, etc…
Hard to study them from an evolutionary perspective, because they may be multifactorial
Monogenic diseases - expressed regardless of environmental conditions (due to pathogen only)
Polygenic diseases - multifactorial, show significant effects due to environmental causes
Diseases of civilization are polygenic
Life style factors are important in the onset and progress of CDD’s
The discord between our genes and lifestyle factors like diet, exercise, exposure to toxins from smoking, drinking etc. all promote CDD’s
Genes that selected for survival in young primate foragers were favored, bad effects didn’t kick in until extreme old age, which most animals never reached in the wild
The basic problem today is that we live much longer than we used to
We live longer now than ever before in human history
Finland has an exceptionally high level of heart disease for some unknown reason
Study found antibodies against Chlamydia compounds in 70% of Finland heart-attack victims
Not conclusive by itself, by middle age 40% of global population has the same antibodies
Coincidence or cause and effect?
Hard to say…C. pneumoniae follows a 6-7 year infection cycle, doesn’t correspond to the pattern of heart attacks
Perhaps heart attacks are associated with chronic infections of C. pneumoniae (Saikku 1993)
This hypothesis created an uproar, and is still highly controversial
C. pneumoniae was found in the arteries of coronary bypass patients in 1992 - coincidental?
About 40 studies published since then have touched on this link, ~ 75% supported it
C. pneumoniae would explain why inflammation is always associated with atherosclerosis - maybe the bacterium causes the inflammation that starts it
C. pneumoniae is attracted to lipids, might explain why fat accumulates in damaged arteries
C. pneumoniae oxidizes fats, might explain association between atherosclerosis and oxidized fats in the arteries
C. pneumoniae develops extremely well in the damaged lungs of smokers, might explain why smoking is a risk factor in heart disease
C. pneumoniae might even explain how second-hand smoke might cause atherosclerosis in others - bacteria travels via aerosol in the coughs of smokers
C. pneumoniae could even explain why daily aspirin reduces the risk of heart attacks - it reduces the inflammation caused by the bacterium
It remains to be seen whether CDD’s are caused by infectious pathogens, or are merely one more legacy of our biological evolution, or one more health problem aggravated by our cultural evolution
It has been a mere 10,000 years since we forsook the role of hunter-gatherer for the staid and settled world of agriculture and urbanization
In some ways, our bodies still live on the great plains of Africa…
Our daily environment has changed radically in the scant millennia of our human civilizations
In evolutionary terms, our bodies have not always kept pace with many of these environmental changes
We must cope with these new environments as best we can, in bodies designed over millions of years for a vanished way of life