Taphonomy

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

2. 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

3. 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

4. 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

5. Autochthonous • where death occurred • Allochtonous • different from where death occurred

6. 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

7. 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)

8. 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

9. 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

10. 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.

12. 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

14. 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

15. 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

16. 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

20. 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