Taphonomy

Defined by Efremov (1940) as “the study of the accumulation and modification of osteological assemblages from a site formation perspective.”

Goals of Taphonomy

• Reconstruct paleoenvironments• Determine which factors cause the

differential destruction or attrition of bone• Understand selective transport of remains• Discriminate human from nonhuman agents

of bone modification

Forensic Anthropology and Taphonomy

• Forensic Anthropology shares the last three of these goals, but are also interested in:– decomposition rates and patterns

– disarticulation

– dispersion of body parts

– modification of soft tissue and bone

• In order to show– time and circumstances of death

– postmortem vs. antemortem/perimortem conditions

– identifying factors

Forensic Taphonomy

• Can therefore be described as the use of taphonomic models to – reconstruct postmortem interval– reconstruct conditions before and after

deposition– discriminate the products of human behavior

from those created by the earth’s biological, physical, chemical and geological subsystems

• Autochthonous– where death occurred

• Allochtonous– different from where death occurred

A Forensic Taphonomic Model

• Four dimensions– objects

• human remains

– space• on the surface• within other environments (e.g. water)• buried• allocthonous vs. autochthonous

– modification of objects– cultural dimension

• cause and manner• investigator bias

• Two major temporal concerns– perimortem interval

• includes the timing of specific events such as trauma as they relate to the time of death

– postmortem interval• ordinal (sequence of events)• interval (absolute time)• ratio (relative to some other temporal sequence)

Perimortem Interval

• Estimating time of injury is difficult in the best cases

• Must be able to determine conditions under which certain taphonomic conditions come into play– but these processes are not precise, so the

boundry between life and death becomes blurred

Postmortem Interval

• Also imprecise• After death, the muscles of the body

become flaccid• Within 1-3 hours the muscles become

increasingly rigid and the joints freeze– rigor mortis

• All muscles begin to stiffen simultaneously, but it is noticeable in smaller muscle groups first

Rigor mortis

• Complete rigor takes 10-12 hours to develop under ideal conditions– 70-75 degrees Fahrenheit

• The body remains stiff 24-36 hours• Heavily impacted by temperature and other

environmental conditions, body size, activity prior to death, etc.

Livor Mortis

• Also known as lividity• discoloration of the body after death due to

gravitational settling of blood• Usually noticeable approximately 1 hour

postmortem, apparent early often• Becomes fixed in about 8-10 hours• Visible until decomposition changes the

color of the body

Algor Mortis

• Normal cooling of a body which takes place as the body equilibrates with the external temperature

• Occurs at an approximate rate of 1.5 degree F an hour– this is obviously dependant on external

temperature

Decomposition

• In general, occurs in stages– after rigor passes, green discoloration of the skin

become evident• generally begins on the abdomen about 24 hours after death

– The body will begin to swell (bloat) due to production of gas by bacteria in the large intestine• may begin within 96 hours after death, sooner if warm or wet

– As the body bloats, the outer layers of the skin begin to slip off the body, as will the hair and nails

• Also during bloat body fluids may purge through the nose and mouth and other orifices.

• At about the same time, the blood within vessels degenerates and darkens, giving the skin a marbled appearance

Order of Decomposition

• Intestines, stomach, accessory digestive organs, heart, blood, circulatory system

• air passages and lungs• kidneys and bladder• brain and nervous tissues• skeletal muscles• connective tissues