Analytical standards needed for 'reading' Pliocene bones

Apr 05, 2012
Jackson Njau points to marks on a fossil bone. Credit: Stan Gerbig, Indiana University

Researchers studying human origins should develop standards for determining whether markings on fossil bones were made by stone tools or by biting animals, Indiana University faculty member Jackson Njau writes in an article this week in the journal Science.

Njau, a co-director of field research at paleontological sites in eastern Africa's Olduvai Gorge, notes that the lack of agreement on interpreting such marks is leading to great uncertainty over when early hominids began using tools to kill and butcher animals -- a fundamental step in .

"There's really no solid, standard method of analyzing these bones that is used by all researchers," he said. "And there is no universal guide, nothing that is part of one's training as a student, that tells you reliably how to judge one type of mark from another."

Njau joined the faculty of the IU Bloomington Department of Geological Sciences in the College of Arts and Sciences as an assistant professor in the fall. He also is a research associate with Stone Age Institute in Bloomington and the Center for Research into the Anthropological Foundations of Technology at IU. He is former principal curator of the National in Arusha, Tanzania.

His Science Perspectives article, published in the April 6 issue and titled "Reading Pliocene Bones," contends that the "way forward" is through further experimentation, integration of different disciplines to better understand the fossil record, and blind testing of bone samples by researchers and students.

He proposes creating a comprehensive collection of samples, developed from experiments on various forms of modification, and making it available to researchers and students through the sharing of samples and the posting of photographs and information online.

Njau points out that the lack of standard criteria has produced estimates of the earliest use of that vary by nearly 1 million years. The consensus is that the earliest evidence of tools associated with butchered bones come from Gona, Ethiopia, 2.6 million years ago, discoveries published by Sileshi Semaw of the Stone Age Institute and others. But a 2010 paper argued that 3.4-million-year-old from Dikika, Ethiopia, showed tool markings, an interpretation that has been challenged by other research groups.

Generally used criteria describe tool marks as V-shaped cuts containing microscopic striations. Percussion marks made by stone hammers are said to consist of pits and grooves, also with micro-striations. But Njau has shown through experiments that the sharp teeth of crocodiles can inflict a range of bite marks closely mimicking tool marks.

This suggests that researchers need to rely on more than the appearance of Pliocene and early Pleistocene bones to determine whether they were marked by stone tools, he says. It's also important to consider the quality of the samples and the context in which they were found. For example, how many bones show what appear to be tool marks? Have stone tools been found in the same area and from the same time? Were crocodiles or other animals present that could have caused the marks?

Explore further: How were fossil tracks made by Early Triassic swimming reptiles so well preserved?

Related Stories

Anthropologist challenges Lucy’s butchery tool use

Nov 16, 2010

( -- An anthropologist in Spain has challenged recent evidence the ancient hominin species Australopithecus afarensis, represented by "Lucy," used sharp stones to butcher animals for meat some 8 ...

Crocs and fish key to human evolution

Jun 01, 2010

( -- A team of scientists now know what may have helped fuel the evolution of the human brain two million years ago. Archeologists working in Kenya unearthed evidence that our human ancestors ate ...

Handier than Homo habilis?

Sep 08, 2011

The versatile hand of Australopithecus sediba makes a better candidate for an early tool-making hominin than the hand of Homo habilis.

Recommended for you

Ancient wheat points to Stone Age trading links

Feb 26, 2015

(AP)—Britons may have discovered a taste for bread thousands of years earlier than previously thought, thanks to trade with more advanced neighbors on the European continent.

Who's your daddy? Hippo ancestry unveiled

Feb 24, 2015

A great-great grandfather of the hippopotamus likely swam from Asia to Africa some 35 million years ago, long before the arrival of the lion, rhino, zebra and giraffe, researchers said Tuesday.

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet Apr 05, 2012
I'll bet if he contacts some coroners or medical examiners, they would be able to give him a wealth of information.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.