Patrick Fahey is excellent at figuring out historic animal stays.
He has analyzed and recognized tens of hundreds of fossils from archaeological websites like Pinnacle Point, a chosen World Heritage Site situated on the southern coast of South Africa. The archaeological website consists of a sequence of caves and rock shelters the place fashionable people lived 50,000 to 160,000 years in the past.
As an anthropology PhD candidate, Fahey makes use of info from these bone fragments to assist reconstruct human ecology from 100,000 years in the past at Pinnacle Point 5-6, a rock shelter on the website.
However, he — like different zooarchaeologists and paleontologists — has confronted a irritating problem: Most animal bones discovered at historic websites are badly damaged into small fragments. Teeth and skulls, helpful for figuring out species, are uncommon. What survives most frequently are fragments from the dense center sections of lengthy bones, often known as shafts.
“If the bone is complete, it’s pretty easy to get information from. You simply look at the bone and you compare it to modern skeletons,” stated Fahey, an affiliated student on the Institute of Human Origins and PhD candidate on the School of Human Evolution and Social Change. “But that is hardly ever the situation. In reality, a single bone may break into dozens or even hundreds of tiny pieces, leaving researchers to work only with those small bits that have survived for millennia. This fragmentation, and the loss of many parts of the original bone, makes direct comparison with modern skeletons difficult or impossible.”
Though the fragmentation makes it tough to establish the species the bone fragments got here from or to even estimate the animal’s measurement, even small fragments can include vital details about the previous — and ignoring them can lead to biased conclusions.
So, Fahey discovered a solution.
He developed a mathematical system that helps scientists worldwide do their jobs extra precisely. The system makes use of a measurable characteristic of the bones — the thickness of the partitions that type the center shaft of lengthy bones referred to as cortical thickness — to estimate an animal’s physique measurement.
The new methodology relies on a simple concept: Bigger animals want stronger lengthy bones to assist their weight. That power comes, partly, from thicker bone partitions. The exact relationship between cortical thickness and physique mass, outlined mathematically, makes it doable to predict the animal’s measurement from fossil stays.
A easy measurement with massive potential
To develop and check the brand new methodology, Fahey measured cortical thickness on greater than 400 fashionable bones from 122 species of land mammals, starting from tiny shrews to African elephants. There was a remarkably constant relationship between wall thickness and physique mass, whatever the animal’s species or which limb bone was measured.
Two mathematical fashions have been created, one estimates an animal’s physique weight and the opposite locations the animal right into a common measurement class. Tests present that these fashions stay correct even when bones are extremely fragmented. Fahey additionally created an internet software for the system the place scientists can add their knowledge and obtain outcomes.
“It’s a pretty simple way to estimate animal size from fossils, and one that has been applied by other scientists using different parts of the skeleton, but not before using cortical thickness,” stated Fahey. “I think it was generally assumed that the relationship wouldn’t be very strong, given the variability between species and between bones. But I found there was less variability in cortical thickness than expected, and the approach worked surprisingly well. Sometimes super useful scientific discoveries come from simply testing our assumptions.”
Overall, this new strategy improves accuracy, reduces subjectivity and makes it simpler to evaluate findings throughout completely different archaeological websites.
“Thirty-five years ago, my students and I showed that these small shaft fragments are critical to our analysis of ancient human behavior, but we lacked formal methods for assigning them to body size, which is critical,” stated ASU paleoanthropologist Curtis Marean, Fahey’s school advisor and co-author of the research. “So I helped lead Patrick to the important question, and he sealed the deal with great work.”
Marean is a analysis scientist on the Institute of Human Origins, and Foundation Professor and Virginia M. Ullman Professor of Natural History and the Environment on the School of Human Evolution and Social Change.
“Prior to this formal model, we used the ‘eyeball’ method, which is what we call more formally ‘expert knowledge,’” Marean stated. “The problem is that expert knowledge varies by expert and is difficult to test for accuracy and precision. Patrick’s paper shows that the experts varied a lot in their abilities, and his model takes out the guesswork and gives everyone a tool they now can use to get it right.”
Knowing the dimensions of animals people interacted with previously is essential, Fahey defined. It helps scientists perceive what early people ate, how they hunted and the way they responded to adjustments in local weather and setting.
At an evolutionary stage, people are uncommon predators: Most predators keep away from prey a lot bigger than themselves, however people recurrently hunt the biggest animals on the panorama. Understanding how this conduct developed might maintain vital clues to our ecological success as a species.
“I’m really excited because this formula is going to simplify the process of identifying animal remains so much,” Fahey stated. “It is scalable to massive assemblages, it’s super cheap and you don’t need any equipment besides calipers. I hope it becomes widespread. We made it usable by anybody across the world, it doesn’t matter about the geographic location or the time period of the specimens.”
The article, “Diaphysis cortical thickness as a predictor of body-size in terrestrial mammals and its application to zooarchaeology,” was not too long ago revealed within the Journal of Archaeological Science.
Along with this latest work, Fahey was additionally a co-author on a brand new publication in Science Advances and produced a number of the research’s informational graphics. The article, “Earliest evidence for intentional cremation of human remains in Africa,” sheds new gentle on the mortuary practices of a 9,500-year-old hunter-gatherer neighborhood in central Africa.