New paleontological techniques unearth surprising information about ancient diets.
Image credit: Brett Eloff, Lee Berger and the University of the Witwatersrand
The first specimen of A. sediba was reclaimed from ancient soil in the Malapa caves, South Africa, in 2008.
In total, six skeletons have been recovered from the same location, all dated to around 2 million years ago.
For their impressive age, the skeletons are miraculously complete and have been investigated to the fullest extent of paleontological technology.
Some scientists believe that these creatures played a pivotal role in the evolution of humanity.
Because of the facial features, upright walk and relatively slight frame of A. sediba, the species is considered a strong candidate to bridge the gap between earlier australopithecines, who arrived on the scene around 4 million years ago, and our more recent relatives, such as Homo habilis.
Studying anything through the murky mists of time is a challenging and technical affair. The knowledge we have amassed about ancient lives is hard-won and open to constant revision as new data and experimental methods arrive.
Australopithecus sediba's teeth
A. sediba's teeth have been studied in some detail. Research, published in 2012, investigated dental microwear in an attempt to garner information about the population's diet.
Minute chips and marks on the teeth can give clues about the textures and types of food being consumed.
The data collected in the 2012 study pointed to a diverse diet of hard foods, mixed with some softer woodland wares, such as bark, fruits and leaves.
New research, conducted by David Strait, professor of anthropology at Washington University in St. Louis, MO, has reopened the debate by studying the remains from a different angle.
The team used biomechanical techniques and a computer-based model of the skull; the methods are similar to those used by engineers to check the strength and breaking points of airplane or car components.
Previous work has shown that australopithecines had impressive adaptations in their jaws, faces and teeth that allowed them to process hard foods and difficult-to-crack nuts. But, according to team member Justin Ledogar, the latest results showed that:
"If (A. sediba) had bitten as hard as possible on its molar teeth using the full force of its chewing muscles, it would have dislocated its jaw."
The paper, published in Nature Communications, could signal a change in our understanding of the foods that A. sediba consumed. A. sediba is already an outlier within the australopiths. Her lighter frame and less muscular attributes make her instantly appear more human than the stockier, more muscular members of other australopith groups.
Australopith populations in other regions, at a similar point in time, were adapting in exactly the opposite direction. Their jaws and teeth were becoming ever more powerful. Questions about adaptations to diet and the impact they might have on evolutionary changes abound.
This study was not designed to measure or theorize about the connections between our own species and A. sediba, but it is intriguing to note that modern humans also have similar restrictions in their bite function.
The ongoing ancient diet debate
Although microscopic damage on the teeth of A. sediba demonstrate that these individuals had indeed eaten hard foodstuffs shortly before they died, the mechanical evidence tells us that their bite force was not powerful enough for hard foods to be a regular part of their diet.
Whether anatomical, microscopic or mechanical information provide the best clues to ancient behaviors is up for debate. All of the approaches seem valid, but they do not necessarily agree with each other.
The facial muscles and jaw anatomy predict one kind of diet, and the microwear studies say something else.
Medical News Today asked Strait whether his research would help make sense of the discussion; he believes that the debate is likely to continue for "several more years." But, he also said that "various research teams are undertaking experimental studies designed to examine the mechanical basis of microwear." He hopes that this will add clarity.
Paleontology and technology
No doubt, the relevance and power of each of the methodologies will eventually be teased out, giving a thorough understanding of how our most ancient ancestors moved, lived and dined.
Modern techniques are taking paleontology to previously unimagined realms, gleaning information that might have been considered impossible just a few decades ago. When MNT asked Strait about the future of research and what these new mechanical tools might show us, he said:
"We can study how different bones of the lower limb respond to loads during walking or running in a variety of extinct human ancestor. We can study how resistant their tooth crowns are to cracking.
We could ask whether or not the production of stone tools produced characteristic stresses in the bones of the hand of various species. The sky is the limit in terms of applying engineering approaches to evolutionary questions."
As for Strait's future projects, he told MNT that he plans to "examine crania in species of the genus Homo, the genus to which we belong."
The results are sure to be as insightful as they are fascinating. MNT recently covered research that used genomic sequencing to reveal clues about the origins of the Irish population.