Welcome Paige Madison to Nutcracker Man! This guest post addresses a key region for the understanding of human evolution, the Afar Triangle. It is the first time this area has a focused-review on the blog, and certainly it will not be the last one…
The Afar Depression (also known as the Afar Triangle) is one of the most important areas for the study of paleoanthropology worldwide. Located in East Africa, the Afar Triangle is a part of the Great Rift Valley. The area sits on top of a junction where three continental plates meet, called a triple rift junction. At this triple rift junction, a widening rift in the Earth’s crust is currently forming. The Awash River runs through the Afar region, and near the banks of the river many important hominin fossils have been discovered.
Excavations in the Afar Triangle began in the 1970s, and discoveries continue to accrue to the present day. The hominin fossil record at Afar stretches back millions of years, representing the most continuous record of hominin habitation anywhere in the world.
1. Ardi: Ardipithecus ramidus. Discovered at a site near the Awash River called Aramis, “Ardi” was recovered from sediments dating to 4.4 million years old. The team who discovered Ardi in 1992 was led by Tim White and Gen Suwa at Berkeley. The skeleton’s name is derived from the local Afar language; “ardi” means “ground” and “ramid” means “root.” Ardi’s skeleton tells us that Ardipithecus had the ability to walk bipedally—on two legs—but probably spent a lot of time in the trees.
2. Lucy: Australopithecus afarensis. The truly iconic skeleton of Lucy was uncovered in 1974 at the site called Hadar, close to the Awash River. Discovered by Donald Johanson of the Institute of Human Origins, Lucy dates back to 3.2 million years old. Lucy’s relative completeness tells us that some hominins were fully, habitually bipedal by 3 million years ago.
3. Selam: Dikika baby: Australopithecus afarensis. Just across the river from Hadar, the most complete skeleton of an early hominin turned up at the site of Dikika in 2003. Discovered by Zeresenay Alemseged, of the California Academy of Sciences, the Dikika individual was very young, possibly about three years old. Nicknamed Selam, this individual tells scientists that Australopithecines grew up quickly, like chimpanzees and gorillas and unlike humans (who have an extended growth period).
4. First Family: Australopithecus afarensis: One year after Lucy was found, a team at the Institute of Human Origins discovered another amazing find, a collection of at least 17 A. afarensis individuals at a single site! The individuals are a mixture of young and old, and therefore provide information about variation within an Australopithecine population.
These discoveries are just a few of the rich hominin finds that have been uncovered in the Afar Triangle. Though these highlights have featured A. afarensis, many other taxa are represented in the area!
Afar Environment and Dating the Fossils
By examining fossils of other creatures that lived in the region—such as pigs—scientists are able to reconstruct the environment of the Afar when hominins roamed the area. Scientists use methods such as examining fossilized teeth to determine the kinds of plants local creatures ate. Scientists have learned that areas such as Hadar has not always been a dry desert, but instead was a wet, wooded environment during the time hominins were evolving.
One of the most remarkable features of the Afar region is the fact that fossils can be dated accurately and precisely. The presence of numerous volcanoes in the Afar region has resulted in some of the most accurate dates for hominin fossils anywhere in the world. The dating method used in the Afar region is called potassium argon dating, which takes advantage of the unique chemical signature of each volcanic eruption, and calibrates those eruptions on a time scale.
The Afar Today
Excavations are ongoing in the Afar Triangle through to the present day; with recent finds such as the Ledi-Geruaru jaw having been uncovered within the last few years! Continuing excavations by teams at Berkeley, the Institute of Human Origins, and other organizations, will hopefully continue to add to scientists’ knowledge about human evolution for decades to come.
About the Author
Paige Madison is a PhD candidate studying the history of paleoanthropology at Arizona State University. She blogs at fossilhistory.wordpress.com and tweets about the history of science @FossilHistory!