Understanding Evolution

Research Profiles : CSI: Olduvai Gorge :

After death, the life of a fossil

Jackson at his lab in Indiana University points out bone markings that provide clues to how the animal died

Jackson at his lab in Indiana University points out bone markings that provide clues to how the animal died.
Figuring out whether an early human was killed by a crocodile, hyena, spear, infectious disease, or something else entirely often involves piecing together clues from many lines of evidence, much as a detective might reconstruct the scenario leading up to a murder. However, investigating a two million year old death is a bit more challenging than modern crime-busting because the passage of time has hidden or destroyed most of the clues. The data that remain tend to be taphonomic in nature.

Taphonomy is the study of the process of fossilization, from the death of the organism to the moment of the fossil's discovery and everything in between. Does the fossil bear distinguishing tooth marks or telltale signs of butchery with the stone tools of early hominids? Is it etched in a way that might have been caused by digestive enzymes? From which part of the body does the fossil come, and what might that tell us about the cause of death? Was the fossil transported elsewhere after the death of the organism? Did this bone break occur before or after the fossil was deposited? Why are the fossils positioned relative to one another in this way? The answers to such taphonomic questions can provide information about how an ancient ecosystem functioned: what different organisms ate, how they interacted with one another, how they behaved, where they lived, and, hence, what factors shaped different species' evolution and behavior.

Jackson excavating at Olduvai Gorge

Jackson excavating at Olduvai Gorge.
Jackson is particularly interested in taphonomic clues that hint at the relationship between the hunter and hunted — as he puts it, "what kind of signatures they leave behind and what kind of story they can tell us about predation in the past." This theme means that a lot of Jackson's research focuses on teeth and the marks they make. Bite marks on bone surfaces represent a direct link between the tooth of the feeding organism and the remains of the victim, often revealing the identity of carcass consumer. Taphonomists also use bite marks to reconstruct the cause of the animal's death (it's not always the animal that wound up eating the carcass!) and the ecological conditions of predator-prey interactions.


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Photo of Jackson pointing out bone markings courtesy of Indiana University; photo of Jackson at Olduvai Gorge courtesy of Jackson Njau

Understanding Evolution © 2015 by The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California