A new analysis of the past 12 million years' of vegetation change in the cradle of humanity is challenging long-held beliefs about the world in which our ancestors took shape – and, by extension, the impact it had on them.
The research combines sediment core studies of the waxy molecules from plant leaves with pollen analysis, yielding data of unprecedented scope and detail on what types of vegetation dominated the landscape surrounding the African Rift Valley (including present-day Kenya, Somalia and Ethiopia), where early hominin fossils trace the history of human evolution.
"It is the combination of evidence both molecular and pollen evidence that allows us to say just how long we've seen Serengeti-type open grasslands," said Sarah J. Feakins, assistant professor of Earth sciences at the USC Dornsife College of Letters, Arts and Sciences and lead author of the study, which was published online in Geology on Jan. 17.
Feakins worked with USC graduate student Hannah M. Liddy, USC undergraduate student Alexa Sieracki, Naomi E. Levin of Johns Hopkins University, Timothy I. Eglinton of the Eidgenössische Technische Hochschule and Raymonde Bonnefille of the Université d'Aix-Marseille.
The role that the environment played in the evolution of hominins—the tribe of human and ape ancestors whose family tree split from the ancestors of chimpanzees and bonobos about 6 million years ago—has been the subject of a century-long debate.
Among other things, one theory dating back to 1925 posits that early human ancestors developed bipedalism as a response to savannas encroaching on shrinking forests in northeast Africa. With fewer trees to swing from, human ancestors began walking to get around.
While the shift to bipedalism appears to have occurred somewhere between 6 and 4 million years ago, Feakins' study finds that thick rainforests had already disappeared by that point—replaced by grasslands and seasonally dry forests some time before 12 million years ago.
In addition, the tropical C4-type grasses and shrubs of the modern African savannah began to dominate the landscape earlier than thought, replacing C3-type grasses that were better suited to a wetter environment. (The classification of C4 versus C3 refers to the manner of photosynthesis each type of plant utilizes.)
While earlier studies on vegetation change through this period relied on the analysis of individual sites throughout the Rift Valley—offering narrow snapshots—Feakins took a look at the whole picture by using a sediment core taken in the Gulf of Aden, where winds funnel and deposit sediment from the entire region. She then cross-referenced her findings with Levin who compiled data from ancient soil samples collected throughout eastern Africa.
"The combination of marine and terrestrial data enable us to link the environmental record at specific fossil sites to regional ecological and climate change," Levin said.
In addition to informing scientists about the environment that our ancestors took shape in, Feakins' study provides insights into the landscape that herbivores (horses, hippos and antelopes) grazed, as well as how plants across the landscape reacted to periods of global and regional environmental change.
"The types of grasses appear to be sensitive to global carbon dioxide levels," said Liddy, who is currently working to refine the data pertaining to the Pliocene, to provide an even clearer picture of a period that experienced similar atmospheric carbon dioxide levels to present day. "There might be lessons in here for the future viability of our C4-grain crops," says Feakins.
Funding for this research was provided by the U.S. National Science Foundation HOMINID Grant 0218511 and from USC.
Robert Perkins | EurekAlert!
UCI and NASA document accelerated glacier melting in West Antarctica
26.10.2016 | University of California - Irvine
Ice shelf vibrations cause unusual waves in Antarctic atmosphere
25.10.2016 | American Geophysical Union
Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.
This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...
Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion
Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
26.10.2016 | Physics and Astronomy
26.10.2016 | Earth Sciences
25.10.2016 | Earth Sciences