So far ranging and residence patterns amongst early hominins have been indirectly inferred from morphology, stone tool sourcing, comparison to living primates and phylogenetic models. An international team of researchers including Sandi Copeland, Vaughan Grimes and Michael Richards of the Max Planck Institute for Evolutionary Anthropology in Leipzig/Germany have now investigated landscape use in Australopithecus africanus (with fossils from sites dating between 2.8-2.0 million years ago) and Paranthropus robustus (with fossils from sites dating between 1.9-1.4 million years ago) from the Sterkfontein and Swartkrans cave sites in South Africa using strontium isotope analysis.
Skull of a Paranthropus robustus from Swartkrans Cave in South Africa. Darryl de Ruiter
This method helps identify the geological substrate on which an animal lived during tooth mineralization. The researchers show that a high proportion of small, but not large, hominin teeth had non-local strontium isotope compositions. Given the relatively high levels of sexual dimorphism in early hominins, the smaller teeth probably represent females, indicating that females were more likely than males to disperse from their natal (i.e. where they were born) groups. This is similar to the dispersal pattern found in chimpanzees, bonobos, and many human groups, but dissimilar to that of most gorillas and other primates. (Nature, June 2nd, 2011)
Established paleontological and archaeological techniques provide little tangible evidence for how early hominins used and moved across landscapes. For example, home range size has been estimated based on a rough correlation with body mass, and models of early hominin dispersal have relied on behaviors common among hominoids and presumed to be present in a common ancestor. “However, the highly uncertain nature of such reconstructions limits our understanding of early hominin ecology, biology, social structure, and evolution”, says Sandi Copeland of the Max Planck Institute for Evolutionary Anthropology.
Copeland and colleagues have now used a geochemical proxy, strontium isotope analysis of tooth enamel, to investigate early hominin landscape use. Strontium is ingested and incorporated in trace quantities into mammalian teeth. First, the researchers determined strontium isotopes in plant specimens that were collected within a 50 km radius of the Sterkfontein and Swartkrans caves in order to establish the background of biologically available strontium across the region. They then sampled a series of hominin tooth crowns by employing a relatively new method for measuring strontium isotopes in teeth that is called laser ablation multicollector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS). This method is almost non-destructive as it leaves only tiny traces on the enamel surface. The researchers found that although there is no significant difference between the proportion of non-locals in P. robustus (36 %) and A. africanus (25 %), there are significant differences between subsets of hominins defined by tooth size.
“The strontium isotope data suggest differences in landscape use between males and females”, says Sandi Copeland and explains: “Because strontium was incorporated into the teeth before adulthood, when the hominins were probably travelling with their mothers, the data are unlikely to reflect differences in foraging areas between adult males and adult females. Rather, the strontium isotopes probably indicate that females preferentially moved away from residential groups”.
The hominins’ female but not male dispersal pattern is similar to the one found in chimpanzees, bonobos, and many human groups, but dissimilar to that of most gorillas and other primates. This suggests that early hominin social structure was not like that of gorillas in which one or few males dominate groups of females.
The small proportion of non-local large hominins could indicate that male australopiths had small home ranges, which would be surprising given that the evolution of bipedalism is commonly attributed to the need to move over large distances. The results could also imply that male australopiths preferred the types of resources found on dolomite landscapes. This study was the first to apply this method to early fossil hominins, and lays the groundwork for future studies of other fossil species, including Australopithecus and Paranthropus in East Africa, and later hominins belonging to our genus Homo.
The following institutions contributed to this study: Max Planck Institute für Evolutionary Anthropology, Leipzig, Germany; University of Colorado, Boulder, USA; Texas A&M University, College Station, USA; Oxford University, Oxford, UK; University of Cape Town, Cape Town, South Africa; University of Zurich, Zurich, Switzerland; Memorial University, St. John’s, Canada; University of British Columbia, Vancouver, Canada.
Original publication:Sandi R. Copeland, Matt Sponheimer, Darryl J. de Ruiter, Julia A. Lee-Thorp, Daryl Codron, Petrus J. le Roux, Vaughan Grimes & Michael P. Richards
Barbara Abrell | Max-Planck-Gesellschaft
Multi-institutional collaboration uncovers how molecular machines assemble
02.12.2016 | Salk Institute
Fertilized egg cells trigger and monitor loss of sperm’s epigenetic memory
02.12.2016 | IMBA - Institut für Molekulare Biotechnologie der Österreichischen Akademie der Wissenschaften GmbH
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
02.12.2016 | Medical Engineering
02.12.2016 | Agricultural and Forestry Science
02.12.2016 | Physics and Astronomy