Chemistry and Trace Elemental Potential in

Paleopathology

The materials we eat, drink, and breath are metabolically transformed during our

lifetimes into chemical markers related to our diet and health. If these markers are able to

survive to the archaeological context, in soil or bone, their chemical content may be

analyzed.

Dietary Analysis

Carbon Isotope Analysis

Nitrogen Isotope Analysis

Calcium and Strontium Analysis

Diagenesis

Pathology

Fluorosis

Lead Poisoning

Miscellanious other poisoning

Trace Elements are utilized primarily in small doses and involved mainly in

enzymatic functions. Although integral in maintaining life, most of these elements are

toxic if ingested excessively- some at very low levels. Zinc Manganese, Iron, Lead,

Mercury, Cadmium, Strontium, Calcium, and Barium are just a few examples of vital

trace elements.

Elemental analysis took the Paleopathological world by storm in the late 1970s with trace

element values accepted as accurate and unadulterated representation of paleodiets.

Contemporary research is more reserved due to a better appreciation for the sources of

induction of trace elements into bone. Food processing and preparation, cooking utensils,

geological variation, natural bone variation, and diagenic processes can all leave trace

element hallmarks in bone. Contemporary research currently focuses on Alkaline-Earth

elements; Multi-elemental analysis; and Single-element analysis.

Lead Poison

 

Basics

Ancient populations had little exposure to lead, however, around 5000BC the

utilitarian uses were discovered.  It has since been adopted into a kaleidoscope of

applications, dramatically increasing the amount of exposure to this element.  Industry

and civilization have both positive and negative facets.  One negative is the havoc lead

wrecks on the body.  Lead can be ingested, inhaled, or simply transferred through touch. 

Unfortunately, the relatively recent introduction has not allowed the human body to

develop a method of dealing with the element.  Instead, lead is simply incorporated

directly into the skeletal system.  Approximately 95% of the lead introduced into the

body is fixed into the hydroxyapatite crystal of bone.  The body takes decades to cleanse

itself of lead fixed into bone, leading to extremely high concentrations of lead over

extended periods of exposure. 

 

Damage

Lead poisoning is most devastating to children, as their minds and nervous

systems are developing at the time of exposure.  Even small amounts of lead, for example

a paint chip the size of a finger nail, can have a dramatic affect on a developing child.  On

the other hand, adults require larger doses in order for lead poisoning to occur. 

Symptoms of lead poisoning include intestinal cramps, nerve paralysis, kidney failure,

and gout. 

 

Low Level Lead Poisoning in Children under Six:

Reduced IQ                                         Behavioral Problems                             Stunted

Growth                        Learning Disabilities     

Attention Deficit Disorder                     Impaired Hearing                                  Kidney

Damage                        

 

High Level Lead Poisoning in Children:

Drastic Mental Retardation                   Coma                                                   Death

 

Adults:

Increased Blood Pressure         Fertility Problems                                  Nerve

Disorders                       Muscle and Joint Problems

Irritability                                  Memory Problems                                Decreased

Concentration

 

Archaeological Context

Lead poisoning is not overtly evident in skeletal remains.  Black lines may be

found in the oral soft tissue, this practice is only applicable in conditions of immaculate

preservation, such as mummies.  Bone weight is another specious indicator.  The most

popular method of identifying lead poisoning is chemical analysis. 

Lead poisoning seems to be a ubiquitous aspect of development.  Each civilization or

generation has succumb to the attractive utility of this element, and they all have borne

the pathology.  The interesting aspect of this truth is the ability to trace the source of lead

in poisoned populations.  For example, Greco-Roman period was marred by lead

poisoning.  The first solid example, exposure to lead is thought to have lead to the

collapse of the Roman empire due to decreased fertility.  People in this time period were

exposed to lead leaching into food and water via drinking-water pipes and dishes.   

Europe’s Industrial Revolution was accompanied by epidemics of colic, paralysis, and

convulsions.  The culprit?  Lead poisoning due to heightened industry as well as pewter

cook ware.

Perhaps the most interesting example of lead poisoning comes from the Caribbean

islands.  Arthur Aufhderheide realized that both slaves and plantation owners from these

islands had extremely high levels of lead in their bones, but different percentages.  He

concluded the different populations were both lead poisoned, only through different

avenues.  In an attempt to be vogue, plantation owners and their families imported

ceramics from abroad, all decorated by lead based paint.  Obviously, slaves were not

given luxurious plates or cups.  Instead, they were exposed to lead via leaching when

distilling rum (sometimes old car radiators).    

Miscellaneous Elemental Poisoning

Arsenic Poisoning

Basics

Arsenic is commonly used as a pesticide and preservative in contemporary

populations. The heavy metal is extremely poisonous and pernicious to the human body.

It can be introduced into the body via ingestion, inhalation, or physical exposure. Unlike

other elements, such as lead and fluoride, arsenic is not incorporated into the bone and is

usually excreted soon after imbibed. Poisoning can occur at levels around 0.5-0.9ppm

within muscle tissue or 0.8-3.8mg/100g of hair. Bones of bodies marked as poisoned by

arsenic exhibit between 9.0ppm and 24.0+ppm.

Damage

Arsenic exposure is often manifested first in gastrointestinal, kidney, and liver

problems. Prolonged exposure causes damage to the peripheral nervous system, skin

lesions, and respiratory inflammation.

Archaeological

The pathology which accompanies arsenic poisoning are relegated to the soft

tissue, therefore, evidence in the archaeological record comes only from mummies or

otherwise preserved bodies. Humans who were poisoned by arsenic during their life and

then mummified (intentionally or otherwise) usually exhibit livers with marked lesions,

abnormal kidneys, skin lesions, and assorted other problems. Archaeological

investigation of arsenic poisoning has been used primarily to validate historical records.

For example, a strong conspiracy theory exists regarding the death of Napoleon. Many

believe his death was precipitated by arsenic poisoning. In order to add credibility to this

theory, strands of Napoleon’s hair have been examined. Unfortunately, there has not

been a uniform agreement in arsenic levels between different strands of hair. Some

indicate levels elevated enough for poisoning, others hardly indicate any problem. In a

similar vein, the remains of the explorer Charles Francis Hall were exhumed in order to

figure out if he died of natural causes, or if he was a victim of an unruly crew. His body

was buried in the Artic, causing rapid freezing and impeccable preservation.

Unfortunately, the soft tissues studied suffered from a similar problems of inconsistency

as those of Napoleon. These inconsistencies are the result of diagenetic problems.

Nitrogen Isotope Analysis

How it Works

The atmosphere has contains two stable Nitrogen isotopes, 14N (99.7 percent of

atmospheric Nitrogen) and 15N (0.3 percent of atmospheric Nitrogen).  These isotopes

are metabolized in a similar fashion to Carbon.  Nitrogen Isotope Analysis is used

primarily to delineate diet in marine settings. 

 

The Delta 15N ratio of organisms is estimated as follows:

Marine Algae 0ppt

Marine Plants 3-10ppt

Marine Predators 10-15ppt

Marine Apex Predators 15-20ppt

 

Using these numbers, high values of Delta 15N ratios indicate a diet based on apex

marine predators (ie seals) while low values indicate a diet focused on seaweeds. 

This technique is hampered by the ability of some organisms in arid climates to recycle

rather than excrete their urea, the primary source of nitrogen.  This practice can skew the

Delta 15N ratio, therefore, this practice is not reliably used in dry coastal regions.

 

 

Fluorosis

 

Basics

In the 1950s, American dentists realized the potential for fluoride to protect teeth

from caries.  However, they soon learned that too much of a good thing can be

dangerous.  Fluorosis is a condition caused by excessive exposure to or ingestion of the

fluoride ion.  Such exposure is most often the result of utilizing drinking water naturally

contaminated with elevated levels of fluoride.  Groundwater of North Dakota is notorious

for it’s high level of fluoride, as are many areas of India, Pakistan, China, Sri Lanka, and

the Great Lakes region of East Africa.  The concentration of fluoride in ground water can

be so capricious that people using one well may be completely healthy while their

neighbors using a separate well exhibit symptoms.

How It Works

Hydroxyapatite crystal is a major component of the inorganic bone and skeletal

system.  A key aspect of this crystal is the hydroxyl ion, an ion whose size and bonding

potential is closely mimicked by the fluorine ion.  Thus, the fluorine ions are able to

replace hydroxyl ions and form fluoroapatite crystal, rather than hydroxyapatite crystal. 

When compared to hydroxyapatite, fluoroapatite is brittle and more dense. 

Dental Fluorosis

The first stage of dental pathology in fluorosis is a loss of the characteristic gleam

on enamel.  Next, the dull appearance turns chalky.  One of the most diagnostic features

of fluorosis is the yellow to brown mottling of teeth.  Fluorine does not stain the teeth,

instead it adversely affects enamel, causing small pits to form across all tooth surfaces. 

These pits soon become home to organic matter, producing the cosmetic yellow to brown

spots.  Unfortunately, if neglected these pits may increase the likelihood of caries.  Dental

pathology on account of fluorosis may occur at levels as low as 0.07mg/kg of

fluoride/body mass a day.   

Fluorosis and You

It may seem counterintuitive to be wary of fluoride, a popular additive to many

diets used to protect teeth.  One must understand fluorosis is only manifested in people

who ingest large amounts of fluoride for an extended period of time, usually beginning

very early in life.  In the initial stages of fluoride supplementation some children

developed mild cases of fluorosis, however, these days supplemented water is kept below

1ppm.  The World Health Organization lists levels above 1.5ppm of fluoride as

dangerous to health for children seven years of age and younger.  These days dental

hygiene products, including toothpaste, are only about 0.15% fluoride.  Therefore, you

should not have to worry about fluorosis from excessive dental hygiene, especially if you

don’t swallow the products.

Skeletal Fluorosis

Fluorosis in the skeleton is characterized by proliferative bone growth, which can

take on several different appearances.  The most characteristic forms of growth are large,

flat sheets across entire bones or small lumps dispersed throughout a bone.  This growth

is spurred by the unique ability of sodium fluoride to stimulate osteoblast action,

therefore bone production.  The impact of fluorosis is usually first seen on cervical

vertebra , followed by the rest of the axial skeleton, and ultimately every bone may be

affected.  Bones with excessive fluoride concentration are usually thick, coarse, and

dense with a surface that resembles broken glass when magnified. The proliferative

nature of bone production affects the motion and flexibility of an individual in ways

similar to osteoarthritis.  Fluorosis has the most dramatic impact on vertebra, where

ligaments are often ossify to the vertebrae, the vertebrae themselves grow to abnormal

size, and eventually ankylosis occurs from cervical vertebrae on down.  This all

contributes to leaving the patient bedridden. 

Archaeological Evidence

Advanced fluorosis is often easily identified in skeletal remains.  Teeth with a

mottled appearance or chalky enamel are a major indication of the affliction.  If such

teeth are found in the same context as bones with massive growth, the evidence is

conclusive.  Diagnosis becomes muddled and complicated if the individual is only

partially affected.  The proliferative bone formation may resemble Diffuse Idiopathic

Skeletal Hyperostosis, causing differentiation to be contentious.  Chemical analysis is one

tactic employed in order to avoid such confusion. 

Case Study

Judith Littleton undertook a major research study where she analyzed skeletal fluorosis in

a community from coastal Bahrain.  The island has been occupied steadily since 7000BP,

however, the study focuses on individuals who lived 2300-1700BP.  At this time,

Bahrainian diets were primarily agriculture based, with some supplement coming from

marine resources.  Dr. Littleton was able to diagnose many cases of fluorosis from this

population.  She sought out excessive examples of ossification of ligaments and

interosseous membranes as well as stained teeth with obvious etiological origin within

the enamel, rather than post-mortem staining.  Only severe cases were accepted in order

to filter out potential arthritic origins for given problems. 

Littleton mapped out the bones most commonly exhibiting evidence for fluorosis,

dividing them into male-female and age categories.  She realized the thoracic vertebrae

showed the highest prevalence of ossification, followed by the sternum, and associated

other bones.  Males were more vulnerable to the affliction relative to females, but both

sexes showed a strong correlation between age and level of disease.  The older an

individual, the more likely they were to exhibit severe degrees of skeletal fluorosis

throughout their body.  In fact, no bones aged younger than 30 exhibited any fluorotic

pathology, those 30-40 only marginal amounts, and only individuals aged 50 and above

suffered from ankylosis. 

Littleton was perplexed because contemporary levels of fluoride in the water do not seem

to be high enough to lead to fluorosis (only 1.5ppm).  After comparing the collection with

DISH, Ankylosing Spondylitis, Pagets Disease, and osteoarthritis Littleton decided

fluorosis was culpable.  She accounted for the surprisingly small amount of natural

fluoride by taking weather into account.  Fluoride levels in the soil and ground water

fluctuate with temperature, precipitation, and so forth.  Therefore, the conditions of the

past may have been more conducive to fluoride leaching into water.  Additionally, the

arid conditions of Bahrain induce the population into drinking excessive amounts of

water to stay hydrated.  In addition, evaporation occurs rapidly.  When water evaporates,

fluoride and other trace elements are left behind, therefore the concentration increases. 

 

 

Diagenesis

How it Works

The processes which allow the inorganic aspect of bone, hydroxyapatite, to fix different

elements into the bone does not stop when an organism dies.  Such postmortem

alterations to bone chemistry is referred to as Diagenesis and can dramatically affect the

research if not accounted for.  The extent of diagenesis is based on the type of

substrate/pH in which a bone is buried, the water table, temperature, and the levels of

given elements in preexisting soil.

There are a few different strategies which may be utilized in order to combat the problem

of diagenesis.  One example is repeatedly washing to remove diagenic strontium, which

has weaker bonds in the bone when compared with biologically bound strontium. 

Another technique is to compare the groups only within a population, who should all

share a common level of contamination due to their similar archaeological context. 

Carbon Isotope Analysis

How it Works

Predicated on differential carbon fixation by C3, C4, and CAM Plants.

C3 plants convert carbon dioxide to a three carbon molecule.  Most trees, shrubs, and

grasses indigenous to temperate or shady environments make up this group of plants.

C4 plants convert carbon dioxide to a four carbon molecule.  Grasses from the subtropics,

which grow at high temperatures and in sunny conditions, are the primarily constituent of

this class.

CAM LOOK THIS ONE UP.  This group is charazterized by cacti and other succulents,

all of which rarely contribute to the diet and therefore have little affect on dietary

analysis.

The different methods of carbon fixing employed by these plant categories result in

different concentrations in carbon isotope ratios.  This ratio is expressed by the Greek

Letter Delta Superscript 13 C and represents 13C/12C ratio.  This ratio is expressed in

parts per thousand and is almost always negative.  Larger negative numbers usually

convey C3 diets: around -21 parts per thousand; while smaller negative numbers convey

C4 diets: approximately -7 parts per thousand.  Mixed diets of both C3 and C4 are

indicated by a ratio around -14ppt.  These numbers are based on strict herbivores,

carnivores usually have slightly less negative values- as they get their carbon from that

previously fixed by herbivores. 

Archaeological Application

Nikolass van er Merwe pioneered this research technique while studying the adoption of

maize in North American Woodlands.  C3 plants are endemic to this region, an

observation supported by Delta 13C values from 5,000 BP which were -21ppt.  This

level was relatively constant until around 1200 BP, when Delta 13C began to become

less negative: -18ppt at 1000BP, -14ppt at 800 BP, and finally -10ppt at 500BP.  These

gradual changes obviate the adoption of a tropical cultigen, in this case the C4 Maize

plant.  This theory is supported by maize in the archaeological context.  Interestingly, the

adoption of maize agriculture indicated by this study allowed population density to

increase.  The bones used to obtain the Delta 13C values support denser populations, as

the later bones are riddled with pathologies relative to the earlier bones.

 

Calcium, Strontium, and Barium Analysis

How it Works

The ratio of calcium to strontium or barium fixed into human bone hydroxyapatite is used

to understand the dietary trophic level of past human populations.  H. Toots and M.R.

Voorhies developed the calcium/strontium chemical analysis and based it on the

following biological understanding:

Plants absorb Strontium from water

Herbivores consume plants, but have a proclivity toward forming bone with Ca rather

than Sr.  This causes a lower Sr level in herbivores than plants.

Further down the trophic line, a carnivore consumes a herbivore.  The same preference

for Ca over Sr occurs in all animals, herbivore and carnivore alike.  Only the strontium

fixed by herbivores is ingested by carnivores, therefore, much lower amounts of

strontium are available to this next trophic level. 

The process continues until the apex predator is reached.  Naturally, this organism has the

lowest ratio of Ca to Sr in any given ecosystem. 

Quick review, strontium is highest in herbivores (400-500ppm)- next omnivores (150-

400ppm)- and lowest in carnivores (100-300ppm). 

Archaeological Application

Ca/Sr relationship has been used in conjunction with grave goods and position order to

further understand societal ranking systems.  Status from the Chalcatzingo site in Mexico

was based on presence or absence of jade on the mortuary context.  People buried with

jade objects had the lowest levels of strontium at the site.  Those interred in prime

locations within a burial mound at the Middle Woodland Gibson site in Illinois indicated

the same phenomenon.  This indicates that higher ranking members of these different

societies benefited from meat rich diets, at least relative to their peers. 

Barium

Barium is another element in the second column of the periodic table, larger than both

Strontium and Calcium.  The difference in size makes Barium the least attractive option

for fixing into hydroxyapatite (calcium preferred followed by strontium).  The

relationship is usually around 10ppm Ca, 5ppm Sr, and 1ppm Ba. 

NEED BIOLOGICAL ANTHROPOLOGY OF THE HUMAN SKELETON book

pages 336-337 for a case study of this