Quick Tips: How To Estimate The Biological Sex Of A Human Skeleton – Skull Method.

This is the 2nd blog post in this Quick Tips series on estimating the biological sex of human skeletal remains. If you haven’t read the first post on the basics of sexing skeletal remains, click here to start at the beginning.

One of the most widely used methods of sexing skeletal remains is by examining the skull. The skull has five different features that are observed and scored.  The five features are the:

Markers together

Each of these markers is given a numerical score from 1 to 5 relating to the level of expression, with 1 being minimal expression and 5 being maximal expression. Each feature should be scored independently, and without influence from the other identifying features. It has been generally found that female skulls are more likely to have a lower level of expression in all features, whereas male skulls are more likely to have higher levels of expression.

To observe the nuchal crest, one should view the skull from its lateral profile and feel for the smoothness (1-minimal expression) or ruggedness (5-maximal expression) of the occipital surface, and compare it with the scoring system of that feature (Figure 1).

The scoring system for expression levels in the nuchal crest.

Figure 1: The scoring system for expression levels in the nuchal crest.

To observe the mastoid process, one should view the skull from its lateral profile and compare its size and volume, not its length, with other features of the skull such as the zygomatic process of the temporal lobe and external auditory meatus. Visually compare its size with the scoring system of that feature (Figure 2). If the mastoid process only descend or projects only a small distance then it should be scored a 1 (minimal expression), where as if it is several times the width and length of the external auditory meatus, then it should be scored as a 5 (maximal expression).

Figure 2: The scoring system for the size and volume of the mastoid process.

Figure 2: The scoring system for the expression levels of the mastoid process.

To observe the supraorbital margin, one should view the skull at it’s lateral profile and place their finger against the margin of the orbit and hold the edge to determine it’s thickness. If the edge feels ‘extremely sharp’ then it would score a 1minimal expression, if it felt rounded and thick as a pencil it would score a 5maximal expression (Figure 3).

Supraorbital Margin

Figure 3: The scoring system for the expression levels of the supraorbital margin.

To observe the supraorbital ridge, one should view the skull from it’s profile and view the prominence of the supraorbital ridge. If the ridge is smooth with little or no projection, then it would score a 1minimal expression, if it is pronounced and forms a rounded ‘loaf-shaped’ ridge then it would score a 5maximal expression (Figure 4).

Supraorbital Ridge - Glabella

Figure 4: The scoring system for the expression levels of the supraorbital ridge.

To observe the mental eminence, one should view the skull front facing, and hold the mandible between the thumbs and index fingers, with the thumbs placed either side of the mental eminence. If there is little or no projection of the mental eminence, then it would score a 1minimal expression, if it is pronounced it would score a 5maximal expression (Figure 5).

Mental Eminence

Figure 5: The scoring system for the expression levels of the mental eminence.

References:

Buikstra, J.E., Ubelaker, D.H. 1994. Standards for Data Collection From Human Skeletal Remains. Fayetteville, Arkansas: Arkansas Archaeological Survey Report Number 44.

Ubelaker, D.H. 1989. Human Skeletal Remains: Excavation, Analysis, Interpretation (2nd Ed.). Washington, DC: Taraxacum.

White, T.D., Folkens, P.A. 2005. The Human Bone Manual. San Diego, CA: Academic Press. Pg 360-385.

This is the second post of the Quick Tips series on sex determination of skeletal remains. The next post in this series will focus on the use of the pelvis and parturition scars to determine biological sex. To read more Quick Tips in the meantime, click here

Quick Tips: How To Estimate The Biological Sex Of A Human Skeleton – The Basics.

Within anthropological and archaeological sciences, ‘sex’ refers to the biological sex of an individual, based on the chromosomal difference of XX being female, and XY being male. Whereas ‘gender’ refers to the socio-cultural differences placed on the biological differences. In recent times, the words ‘gender’ and sex’ have been used incorrectly as interchangeable words within this discipline.

Therefore, it is important to remember that the word ‘gender’ refers an aspect of a person’s social identity, whereas ‘sex’ refers to the person’s biological identity.

Sexual dimorphism as seen in the human skeleton is determined by the hormones that are produced by the body. There are numerous markers on a human skeleton which can provide archaeologists and anthropologists with an estimate sex of the deceased. The areas of the skeletal remains that are studied are the:

 If the skeletal marker listed above is a link, it means that I have already covered it in an individual blog post and can be found by following the link.

The two most commonly used skeletal markers that are observed by osteologists are the skull and pelvic bone, as these show the most extreme differences.

It is generally noted that female skeleton elements are characterized by being smaller in size and lighter in construction, whereas males have larger, robust elements. Due to normal individual variation, there will always be smaller, dainty males and larger, robust females. Therefore, it is always important to observe a variety of skeletal markers to come to an accurate determination.

It should be noted that it is a lot harder to reliably deduce a juvenile/sub-adult’s sex, as many of the differences in skeletal markers only become visible after maturation, when the skeletal changes occur due to puberty. Therefore, use of DNA has been widely used to sex sub-adult skeletal remains as DNA analysis can now detect and identify X and Y chromosome-specific sequences.

References:

Buikstra, J.E., Ubelaker, D.H. 1994. Standards for Data Collection From Human Skeletal Remains. Fayetteville, Arkansas: Arkansas Archaeological Survey Report Number 44.

Ubelaker, D.H. 1989. Human Skeletal Remains: Excavation, Analysis, Interpretation (2nd Ed.). Washington, DC: Taraxacum.

White, T.D., Folkens, P.A. 2005. The Human Bone Manual. San Diego, CA: Academic Press. Pg 360-385.

This is the first of a Quick Tips series on sex determination of skeletal remains. The next post in this series will focus on the use of the skull to determine biological sex. To read more Quick Tips in the mean time, click here

 

Quick Tips: Archaeological Techniques – Ground Penetrating Radar.

Ground-penetrating or probing radar (GPR) is a non-destructive, geophysical method that uses radar pulses to image the subsurface. The principles of ground-penetrating radar are similar to reflection seismology, except that electromagnetic energy is used instead of acoustic energy, and reflections appear at boundaries with different dielectric constants instead of acoustic impedances.

Ground-penetrating radar was applied in the 1940’s after the use of radar to detect enemy aircraft’s during WW2. In 1960’s, due to the progression of this surveying technique, it was primarily used to probe and explore the polar ice. By using GPR in relation to these two applications, a P-38 lightening fighter plane was pinpointed within the ice surrounding Greenland in 1992. The P-38 was originally part of a squadron of six fighters and two B17 Flying Fortresses that ditched just over Greenland in 1942. The P-38 fighter plane was later recovered from a depth of 75m.

How does Ground-penetrating radar work? 

GPR works by emitting high frequency, usually polarized, radio waves via antennas, into the ground. If the area being surveyed contains artefacts or hidden archaeology; these electromagnetic waves are reflected back. When the wave hits a buried object or a boundary with different di-electric constants, the receiving antenna records the variations in the reflected return signal. These returned signals are then collected and interpreted to identify any hidden archaeology within the surveyed area.

N.B. Higher frequencies do not penetrate the ground as far as lower frequencies do, but these higher frequencies give a better resolution. Also the radar emitting antennas are usually in contact with the ground for the strongest signal strength; however, GPR air launched antennas can be used above the ground.

Advantages of Ground-penetrating Radar:

  • GPR is non-destructive and not invasive – helping to preserve the archaeology/landscape.
  • GPR can be used in a variety of media/sediments including; rock, soil, ice, fresh water, pavements and structures.
  • It can detect objects, changes in material, and voids/cracks in the ground.

Disadvantages of Ground-penetrating Radar:

  • The depth range of GPR is limited by the electrical conductivity of the ground. As conductivity increases, the penetration depth decreases. This is because the electromagnetic energy is more quickly dissipated into heat, causing a loss in signal strength at depth.
  • In moist and/or clay-laden soils and soils with high electrical conductivity, penetration is sometimes only a few centimetres.
  • Metal can interfere with the electromagnetic radiation – this can give false results.

References:

Balme, J., Paterson, A. 2006. Archaeology in Practice: A Student Guide to Archaeological Analayses. Oxford, UK: Blackwell Publishing. Pg 218.

Renfrew, C., Bahn, P. 1991. Archaeology: Theories, Methods and Practice. London, UK: Thames & Hudson. Pg 249-53.

Click here to read more Quick Tip posts!

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Quick Tips: How To Estimate The Chronological Age Of A Human Skeleton – Cranial Suture Closure Method.

This is the 4th blog post in this Quick Tips series on chronologically dating human skeletal remains, if you haven’t read the first post click here to start at the beginning. In my previous blog post I introduced the method of chronologically dating sub-adults using dentition, you can find out this information by clicking here.

Another method of chronologically aging human skeletal remains is by observing the cranial suture closure sites. The human skull has seventeen unique cranial fusion sites (Figure 1), that are positioned on the vault, the lateral-anterior sites, and the maxillary suture. The seventeen sites are:

  1. Midlambdoid                                           10.Superior sphenotemporal
  2. Lambda                                                    11. Incisive suture
  3. Obelion                                                    12. Anterior median palatine
  4. Anterior sagittal                                      13. Posterior median palatine
  5. Bregma                                                    14. Transverse palatine
  6. Midcoronal                                              15. Sagittal (endocranial)
  7. Pterion                                                     16. Left lambdoidal (endocranial)
  8. Sphenofrontal                                         17.Left coronal (endocranial)
  9. Inferior sphenotemporal
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Figure 1) Diagram showing the seventeen cranial suture sites.

The first seven fusion sites are on the vault, and the lateral-anterior sites consist of numbers six to ten. Each suture is usually given a numerical score, the score of 0-3 is recommended by the Buikstra and Ubelaker standards (1994). The Buikstra and Ubelaker (1994) scoring system is as follows;

  • 0 is given when the suture is open, meaning there is no evidence of ectocranial closure.
  • 1 is given where there is a minimal closure of the suture.
  • 2 is given to sutures with evidence of significant closure.
  • 3 is given to a completely obliterated suture (complete fusion).

So to attain the age of a skeletal remain you would total the scores for each grouping of sites, vault (1-7) or lateral anterior (6-10), and by comparing the scores to the known composite scores vs. chronological age of Meindl And Lovejoy, 1985 (Figure 2).

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Figure 2: Table demonstrating Meindl and Lovejoy (1985)’s composite scores of the sutures on the vault and lateral-anterior, respectively, in relation to mean chronological age.

A very useful cranial suture site is the sphenooccipital synchrondrosis, because at least 95% of all individuals have fusion here between the ages of twenty and twenty-five, with most individuals experiencing complete fusion around the age of twenty-three (Krogman and Işcan, 1986).

References:

Buikstra, J.E., Ubelaker, D.H. 1994. Standards for Data Collection From Human Skeletal Remains.Fayetteville, Arkansas: Arkansas Archaeological Survey Report Number 44.

Krogman, W.M., Işcan, M.Y. 1986. The Human Skeleton in Forensic Medicine (2nd Ed). Springfield, Illinois: C.C. Thomas.

Meindl, R.S., Lovejoy, C.O. 1985. Ectocranial Suture Closure: A Revised Method For The Determination Of Skeletal Age At Death Based On The Lateral-Anterior Sutures. American Journal of Physical Anthropology. 68, 57-66.

White, T.D., Folkens, P.A. 2005. The Human Bone Manual. San Diego, CA: Academic Press. Pg 360-385.

This is the forth of a Quick Tips series on ageing skeletal remains, the next in this series will focus on the use of the pubic symphyseal surface to chronologically age skeletal remains. To read more Quick Tips in the meantime, click here

To learn about basic fracture types and their characteristics/origins in their own Quick Tips series, click here!

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Quick Tips: Named Fractures – Part One: Hand & Forearms

This blog post is the 3rd in its series on bone fractures. To view the first blog post on the basic fracture types and information, including open and closed fractures, click here.

This blog post will highlight some of the common ‘named’ fractures you will often find in archaeological and anthropological settings. It is important to know their characteristics and common causes to help establish what happened – whether the fracture was received by defensive or offensive action, or purely accidental. This blog post will examine the first five common fractures associated with the hand and forearm bones.

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Common ‘Named’ Fractures of the forearms and hands: A) Boxer’s fracture, B) Bennett’s fractures, C) Parry’s or Monteggia’s fracture, D) Colles’ fractures, and E) Smith’s fractures.

The first two fractures we will look at affect the metacarpal bones;

A)     Boxer’s fracture: This fracture occurs due to the axial loading, meaning a force was applied along/parallel to the axis of the bone, on the transverse neck of the 4th and 5th metacarpal, secondary to an indirect force. A Boxer’s fracture often happens due to punching an object/person with a closed fist, hence the name ‘Boxer’ being associated to it.

B)      Bennett’s fracture: This fracture affects the 1st metacarpal (thumb) and extends into the carpometacarpal (CMC) joint which is complicated by subluxation (dislocation of a joint). A Bennett’s fracture is an oblique (See 1st blog post for meaning, click here) intra-articular metacarpal fracture caused by an axial force directed against the partially flexed metacarpal. This injury is also common when someone punches a hard object, but its most common cause is falling onto the thumb. An example of this is falling off a bike, as the thumb is extended around the handle bars.

The last three fractures affect the longbones of the forearm, the ulna and radius;

C)      Parry’s/Monteggia’s fracture: This fracture occurs on the proximal third of the ulna with subluxation of the radius/ulna. The most common cause of this fracture is by blunt force trauma caused by lifting the forearm up to protect the head or body in defence from an oncoming attack/striking object.

These two fractures affect the distal radius but cause displacement in two directions;

D)     Colles’ fracture: A Colles’ fracture, also known as a “dinner fork” or “bayonet” fracture, occurs when the distal radius is broken with dorsal displacement of the wrist and hand. This fracture is common when the person falls forwards and uses their outstretched hand to cushion the fall, which causes the force to displace and break the head of the radius.

E)      Smith’s fracture: A Smith’s fracture is the same as the Colles’ fracture but with ventral displacement of the broken radius head. The cause of a Smith’s fracture is the same as the Colles’ fracture, but it is less common.

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Fractures: D) Colles’ fracture, and E) Smith’s fracture.

The next Quick Tips post will discuss other ‘named fractures’ in archaeological/anthropological situations and their causes and characteristics.

This is the third post of a set on fractures, so keep your eyes open for the other posts, and the new ones to come. To view all the other Quick Tips posts click here!

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Quick Tips: How To Estimate The Chronological Age Of A Human Skeleton – Epiphyseal Closure Method.

This Quick Tips post is the second in the series on age estimation on skeletal remains, if you haven’t read the previous post click here. The previous post provides an overview of the different techniques utilised by archaeologists/anthropologists, which will each be covered in more detail in their own blog post, and the categories that human skeletal remains are placed under according to their chronological age.

One of the methods frequently used by archaeologists/anthropologists to estimate the chronological age of human remains is by studying the level of epiphyseal fusions.

But first what is an epiphysis? An epiphysis is the cap at the end of a long bone that develops from a secondary ossification center. Over the course of adolescence the epiphysis, which is originally separate, will fuse to the diaphysis. The ages of which epiphyseal fusion begins and ends are very well documented, with the majority of epiphyseal activity taking place between the ages of fifteen and twenty-three.

Epiphyses

Diagram showing where the epiphysis is found.

As epiphyseal fusions are progressive they are often scored as either being unfused (non-union), united, and fully fused (complete union). Females often experience the union of many osteological elements before males, and every individual experience epiphyseal union at different ages.

Left: Diagram of a skeleton showing the position of the different epiphyseal elements. Right: A graph displaying the timing of fusion of epiphyses for various for various human osteological elements. The grey horizontal bars depict the period of time, in ages, when the fusion is occurring. All of the data is representative of males, except where it is noted. Data taken from Buikstra & Ubelaker, 1994.

Left: Diagram of a skeleton showing the position of the different epiphyseal elements.
Right: A graph displaying the timing of fusion of epiphyses for various for various human osteological elements. The grey horizontal bars depict the period of time, in ages, when the fusion is occurring. All of the data is representative of males, except where it is noted. Data taken from Buikstra & Ubelaker, 1994.

Archaeologists/anthropologists use standards that are well known and documented, such as Buikstra & Ubelaker’s (1994) depicted in the above graph. From the above data we know that, for example, the fusion of the femur head to the lesser trochanter is begins around the age of fifteen and a half and ends around the age of twenty. So if a skeleton has evidence of an unfused femur head/lesser trochanter, there is a possibility of the skeleton having a chronological age of < fifteen years. If there is full union of the epiphyses then the skeleton is more than likely being > twenty years old. But it should be noted that individuals vary in their development so numerous elements should be examined before coming to an accurate conclusion.

Different stages of epiphysis fusion of human tibias. Ages left to right: Newborn, 1.6 years old, six years old, ten years old, twelve years old and eighteen years old.

Different stages of epiphysis fusion of human tibias. Ages left to right: Newborn, 1.6 years old, six years old, ten years old, twelve years old and eighteen years old.

As several elements of the human skeleton begin the stages of epiphyseal fusion alongside the conclusion of tooth eruption, these two techniques (dentition and epiphyseal closure) are often used complementary to each other to help age sub-adults. The next post in this series on age estimation will focus on the use of dentition to aid with the chronological ageing of human remains.

References:

Buikstra, J.E., Ubelaker, D.H. 1994. Standards for Data Collection From Human Skeletal Remains. Fayetteville, Arkansas: Arkansas Archaeological Survey Report Number 44.

White, T.D., Folkens, P.A. 2005. The Human Bone Manual. San Diego, CA: Academic Press. Pg 360-385.

This is the second of a Quick Tips series on ageing skeletal remains, the next in this series will focus on the dentition method of ageing sub-adults. To read more Quick Tips in the mean time, click here

To learn about basic fracture types and their characteristics/origins click here!

Quick Tips: Fracture Types – The Basics Pt 2.

In my previous Quick Tips, which you can find by clicking here, you were introduced to the first six basic types of fractures, what the main causes of fractures are, and the two main categories they are classed in. It is important that you know the information in the previous Quick Tips post before learning these last few basic fractures, as it discussed the fundamentals of fractures.

Basic Fracture Types:

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Fracture Types: A) Butterfly, B) Longitudinal, C) Segmented, D) Hairline, and E) Avulsion.

A) Butterfly Fracture: Butterfly fractures usually affect long bones and can be caused by car accidents or by being knocked side on.

B) Longitudinal Fracture: As a transverse fracture is a bone along the horizontal axis, a longitudinal fracture is along the vertical axis.

C) Segmented Fracture: This is when the bone has fractures in two parts of the same bone causing the bone to break into larger bone fragments which are separated from the main body of a fractured bone.

D) Hairline Fracture: These fractures are also known as ‘stress fractures’. These types of fractures are very difficult to diagnose and once they heal there may be no evidence left to see. These are very difficult, if not impossible to identify when in an archaeological context.

E) Avulsion Fracture: Avulsion fractures are characterised as the separation of a small fragment of bone at the site of attachment of a ligament or tendon.

The next Quick Tips post will discuss the ‘named fractures’ that can be discovered in archaeological contexts, such as the familiar Bennett’s and Parry’s fracture, and their origins and common causes.

This post was put together by using knowledge from my degree and supplemented with the textbook ‘The Archaeology of Disease’ by Charlotte Roberts & Keith Manchester. If you’re interested in the latest scientific and archaeological techniques used to understand the diseases of past populations, you should check it out!

This is the second post of a set on fractures, so keep your eyes open for the other posts. To view other Quick Tips posts click here!

Quick Tips: Fracture Types – The Basics.

In my previous Quick Tips post I addressed how to distinguish between ante, peri and post-mortem fractures, click here if you haven’t read it yet. 

In this Quick Tips post I will show you some ways to identify and deduce common fracture types and their key characteristics. The definition of a fracture is a break in the continuity of a bone. There are three major causes of fractures: acute injury (an accident); underlying disease which then weakens the bone making it susceptible to fractures; and repeated stress (as seen in athletes).

All fracture types can be placed in two categories; open and closed. An open fracture, also known as a compound fracture, is where the bone breaks through the skin causing an open wound. It is called an open fracture as there is an open connection between the fracture site and skin. A closed fracture is where the bone has no connection between the outer skin surface and the fractured bone itself; it does not cause an open wound. A closed fracture is classed as a ‘simple fracture’.

Basic Fracture Types:

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Fracture Types: A) Transverse, B) Oblique, C) Spiral, D) Comminuted, E) Greenstick, and F) Impacted fracture.

A) Transverse Fracture: This is when the break of a fracture is in a horizontal line, it is the simplest fracture type.

B) Oblique Fracture: This fracture is a break which extends in a slanting direction.  Oblique fractures are caused by indirect or rotational force.

C) Spiral Fracture: As you can guess from the name, this is a fracture which is characterised by a spiral. It is often denoted as being caused by torsion or force onto the bone.

D) Comminuted Fracture: A comminuted fracture is characterised from the splintering of the bone. This causes the fracture to be made up of two or more pieces. This fracture is common in road-traffic accidents and these fractures are less likely to heal in a functionally satisfactory manner.

E) Greenstick Fracture: This occurs when a transverse fracture is incomplete. This fracture is seen mainly in children due to their young, immature bones which rarely break the whole width.

F) Impacted Fracture: This occurs when the bone is broken and not displaced but the two fractured ends are forced together. This produces a rather stable fracture which can heal readily but there may be some length lost.

This post was put together by using knowledge from my degree and supplemented with the textbook ‘The Archaeology of Disease’ by Charlotte Roberts & Keith Manchester. If you’re interested in the latest scientific and archaeological techniques used to understand the diseases of past populations, you should check it out!

This is the first post of a set, click here to read the second post. To view other Quick Tips posts click here!

Quick Tips: How can you tell if a skeletal fracture is ante, peri or post-mortem?

There is a relatively easy way to see whether a fracture to a skeleton is ante, peri or even post mortem. It is essential to detail and deduce which category a fracture falls into, as this is very important to see whether the fracture had played a part in the person’s death.

To first classify a fracture, we need to understand what the different categories mean. Some of you will already know these terminology, but here’s a quick reminder;

  • If a fracture is ante-mortem, it means that the fracture was made before death of the persons.
  • With peri-mortem fractures, it means that the fracture was received at or near the time of death of the persons – so could have been the fatal strike.
  • Post-mortem fractures are fractures that have been received after death, so during the time from death to the time of recovery. These fractures are usually from excavation processes, dismemberment, or even natural processes (soil, animal and plant activity).

You will be able to determine if a bone fracture was ante-mortem due to there being signs of healing which is shown by cell regrowth and repair.

With peri-mortem fractures, the person died before the healing started to take place, but the fractures will still contain the biomechanics that are present in ante-mortem fractures.

Post-mortem breaks tend to shatter compared to peri-mortem breaks which splinter, this is because bones which are in the post-mortem stage tend to be dry and rather brittle. Another big indicator of a fracture being post-mortem is the difference in colour.

The ‘Quick Tip’ that my applied anthropology lecturer taught me on how to easily distinguish between peri-mortem and post-mortem is to look at the fracture and decide; is it a clean break, as if you were breaking in half a bar of chocolate? If it is, then the fracture is most likely to be a peri-mortem fracture. If the break looks crumbly, like breaking a biscuit in half, it’s post-mortem fracture. Obviously this tip is not the most scientific, but it’s an easy way to begin your distinguishing process.

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Skull with signs of post-mortem fractures. This photo is from a practical lab session.

If you look at the photo above it illustrates a post-mortem fracture. You can determine this easily due to the colour difference on the edge of the fracture, where it is a much lighter colour compared to the rest of the skull and the crumbly nature of the cut.

References:

Most of this is my own knowledge that I learnt during my degree in my anthropology lectures/lab practical sessions. But if you’re looking for a published journal check the one below. It is very informative and easy to understand if you’re a beginner in the world of anthropology/archaeology! It also highlights some problems that can arise when distinguishing trauma, it’s really interesting!

Smith, A.C. 2010. Distinguishing Between Antemortem, Perimortem, and Postmortem Trauma. Academia.edu. Available from here in .pdf form!

Read more anthropology/archaeology quick tips here!