Thanks to newly discovered fossilized bones, scientists have now been capable of meet an intriguing 3.4-million-year-old hominin foot, first present in 2009, from a species that differs from the famous fossil Lucy. This link strengthens the case that two distinct species of early human ancestors were living in the identical region at the identical time.
In 2009, a research team led by Arizona State University paleontologists discovered eight bones from the foot of an ancient human ancestor in 3.4-million-year-old sediments in distant Ethiopia. The fossil, often known as a Bertel nature foot, was recovered on the Varanso Meli paleontological site and was formally introduced in a 2012 publication.
“When we found the foot in 2009 and announced it in 2012, we knew it was different from Lucy's species, Australopithecus afarensis, which has been widely known since then,” said Haley Celsi, director of the Institute of Human Origins (IHO) and a professor within the ASU School of Human Evolution and Social Change.
“However, it is not common practice in our field to name a species based on postcranial elements below the neck—so we were hoping to find something above the neck in clear association with a toe. Crania, jaws, and teeth are the elements typically used in species recognition.”
Attaching the brittle foot
When the brittle foot was first described, some teeth had already been recovered from the identical general area. However, scientists weren't sure if those teeth got here from the very same sedimentary layer because the toe. In 2015, the team announced a brand new species from the region, but had not yet assigned a brittlefoot to the species, regardless that some fossils were found very near the foot, Haley Selassie explained.
Over the following decade, repeated field seasons and extra fossil discoveries allowed the team to construct a stronger picture. Haley Selassie said they now have enough material to confidently link the brittle-foot to the species.
Two hominin species sharing the identical landscape
The decision to put the Brittlefoot in a selected species is barely one part of a bigger story. The Veranso Mill site is especially essential since it provides clear evidence of closely related hominin species living in the identical area at the identical time.
Brittle feet, which at the moment are associated, are considered more primitive than the feet of Lucy's species. Unlike the lacy, Bertelfoot had an opposable big toe, which might have been useful for climbing. On land, nevertheless, it still walks on two legs and seems to have moved off totally on the second toe quite than the massive toe, which is how modern humans typically walk.
“The presence of an abducted big toe in Ardipatex ramides was a big surprise because 4.4 million years ago there was still an early hominin ancestor that retained an opposable big toe, which was completely unexpected,” Haley Selsey said.
“Then 1 million years later, 3.4 million years ago, we got the brittle foot, which is even more surprising. That's when we see species whose members you had completely with one big toe. That meant walking on two legs—it's found in different forms. When the legs were on the ground, there wasn't just one way until later.”
Isotope evidence highlights varied hominin diets
To higher understand what it ate, University of Michigan professor Naomi Levin analyzed eight of 25 teeth recovered from the Bertel area using isotope techniques. The procedure begins by cleansing the surface of the tooth after which removing only the enamel for careful examination.
“I sample the teeth with a dental drill and a very small (<1 mm) bit—the same kind of equipment that dentists use to work on your teeth," Levin said. "With this drill I carefully remove a small amount of powder. I store the powder in a plastic vial and take it back to my lab at the University of Michigan for isotopic analysis."
The results were unexpected.
While Lassi species showed a mixed food plan, with a greater reliance on C3 resources using each C3 (resources from trees and shrubs) and C4 plants (tropical grasses and sedges).
“I was surprised that the carbon isotope signal was so clear and so similar to the carbon isotope data from old hominins and similar data,” Levin said. “I thought the diet and the diet would be difficult to identify, but the isotope data clearly shows that the resources are not being accessed to the same extent, which is an early hominin shown to use C4 grass-based food resources.”
Dating Fossils and Reconstructing Ancient Environments
Another essential a part of the research involves dating the age of the fossils and reconstructing the traditional environment by which these hominins lived. How fossil layers are arranged in space and time helps scientists understand when, and under what conditions, each species was present.
“We've done a lot of careful field work at Veranso Mill to establish how different layers of fossils are related, which is critical to understanding when and in what settings different species lived,” said Beverly Seiler, professor of earth, environmental and planetary sciences at Case Western Reserve University. Seiler led the geologic work that established the stratigraphic association between Pir and
Adolescent jaws offer clues to growth and development
Along with the 25 teeth recovered from Bertel, Haile Selassie's team also discovered the jaw of a juvenile individual, based on the anatomy of the tooth, clearly. According to Gary Schwartz, IHO Research Scientist and Professor within the School of Human Evolution and Social Change, this jaw contained a full set of pre-existing baby teeth, in addition to many adult teeth still developing deep inside the lower jaw.
The researchers used CT scanning technology to visualise all of the developing teeth. Because tooth development is closely related to overall growth patterns, this information helped the team estimate that the young man was about 4.5 to 4.5 years old on the time of death.
“For a juvenile hominin of this age, we were able to see clear signs of a developmental disconnect between the front teeth (incisors) and the back chewing teeth (molars), similar to what is seen in Lucy's species in living apes and other early australopitheans,” Schwartz said.
“I think the biggest surprise was despite our growing awareness that these early australopithecines (that is, early hominins) species, in their size, in their diet, in their locomotor repertoire and in their anatomy — these early australopithecines looked very similar to the way they grew up.”
How Ancient Hominins Lived Together
By combining details about movement (locomotion), food plan and environment, scientists are gaining recent insights into how different hominin species could live in the identical region without driving others to extinction. They could also be allowed to share the landscape by utilizing them in alternative ways in how they walk, climb and feed.
“All our research to understand past ecosystems millions of years ago is not just about curiosity or figuring out where we came from,” said Haley Selassie.
“If we don't understand our past, we can't fully understand the present or our future. What happened in the past, we see happening today,” he said. “In many ways, the climate change we see today happened so many times during Lucy's time and what we learn from that time can help mitigate the worst consequences of climate change today.”
Publication, research team and funding
“Shedding light on newly discovered diets and locomotion,” appears within the journal. The international research team included scientists from Arizona State University, Washington University, St. Louis, Case Western Reserve University, Berkeley Geochronology Center, University de Barcelona, University of Tampa and University of Michigan. The full list of authors is: Johannes Haile Selassie, Gary T. Schwartz, Thomas C. Prong, Beverly Z. Salver, Alan Dino, Louis Gebert, Anna Ragni, and Naomi E. Levine.
Funding for this work got here from the National Science Foundation and the WM Keck Foundation. Field and laboratory research in Ethiopia was made possible by the support of the Ethiopian Heritage Authority.