3.3 Million Year Old Vertebral Column Confirms Human Pattern of Au. afarensis

The science site PhysOrg has posted a story on a study of the 3.3 million year old fossil from the site of Dikika, in the Afar Triangle.  The fossil, known as Selam, is an almost complete skeleton of a 2 ½ year-old child. From the story:

Many features of the human spinal column and rib cage are shared among primates. But the human spine also reflects our distinctive mode of walking upright on two feet. For instance, humans have fewer rib-bearing vertebrae - bones of the back - than those of our closest primate relatives. Humans also have more vertebrae in the lower back, which allows us to walk effectively. When and how this pattern evolved has been unknown until now because complete sets of vertebrae are rarely preserved in the fossil record.

"For many years we have known of fragmentary remains of early fossil species that suggest that the shift from rib-bearing, or thoracic, vertebrae to lumbar, or lower back, vertebrae was positioned higher in the spinal column than in living humans. But we have not been able to determine how many vertebrae our early ancestors had," said Carol Ward, a Curator's Distinguished Professor of Pathology and Anatomical Sciences in the University of Missouri School of Medicine, and lead author on the study. "Selam has provided us the first glimpse into how our early ancestors' spines were organized."

This gives us much better evidence of how bipedality was practiced in some of the earliest hominins. We know, from the footprints at Laetoli and the hip remains of Lucy, that Au. afarensis was bipedal but now we know that the rib structure had evolved into a more human pattern. 

Of Stone Tools and Human Cognition

One of the things that is taught in human origins classes all over the world is that the earliest stone tools were likely made at the site of Dikika, and date to around 3.4 million years ago.  That perspective has now been called into question with the observation that monkeys can create exactly the same kinds of tools—by accident. Sarah Knapton, writing in the Telegraph has this:

In a discovery that calls into question decades of research, a band of wild bearded capuchin monkeys in Brazil were seen hammering rocks to extract minerals, causing large flakes to fly off.

Previously archaeologists believed the flakes were only made by humans through a process called ‘stone-knapping’ where a larger rock is hammered with another stone to produce sharp blade-like slivers which can be used for arrows, spears or knives.

The flakes were thought to represent a turning point in human evolution because they demonstrated a level of planning, cognition and hand manipulation that could not be achieved by other animals.

But the new research suggests that flakes can be made without any such foresight. In fact they can simply be made by accident.

“The fact that we have discovered monkeys can produce the same result does throw a bit of a spanner in the works in our thinking on evolutionary behaviour and how we attribute such artefacts,” said Dr Michael Haslam, lead of the Primate Archaeology project at the University of Oxford.

This is possible and it may be that some of the earliest “tools” aren't any such thing. When hominins started using tools in a concerted fashion has always been a large question in the evolutionary picture. It is very clear that by what we know as the Acheulean, manufactured by Homo ergaster, Homo erectus and Homo heidelbergensis, the hand axes are clearly human-made. Before that, maybe more research needs to be done to verify that what we think is human behavior actually is.  It is natural to want to impart human intelligence to our ancestors as far back as we can, in an effort to “humanize” them but, sometimes, this might be just wishful thinking.

Early Australopithecines Used Stone Tools

Arizona State University is reporting that research done in Dikika, northern Ethiopia, by Curtis Marean and Hamdallah Béarat has determined that animal bone recovered from sediments that date to 3.4 million years old have cut marks indicating the use of stone tools. That would put these in the hands of Australopithecus afarensis. As Carol Hughes writes:

“This discovery dramatically shifts the known timeframe of a game-changing behavior for our ancestors,” said paleoanthropologist Zeresenay “Zeray” Alemseged, director of the Dikika project and director of anthropology at the California Academy of Sciences.

No hominin remains were found with the animal bone fragments that were uncovered 200 meters away from the site where Alemseged and a team discovered “Selam” (Lucy’s baby) in 2000. Lucy was discovered in 1974 a few miles north, near Hadar, by Donald Johanson, the world renowned ASU paleoanthropologist.

“There is no question that the announcement of stone tool use at 3.4 million years ago will unleash a flurry of controversy and genuine disbelief among some scholars,” said Johanson. “However, I believe the team has presented a convincing case of stone tool use during Lucy’s time.

While Johanson is sometimes given to hyperbole, he is quite correct that this represents a quantum jump in intelligence over any previous hominin form and will generate new models of early hominin behavior. Even if A. afarensis was just scavenging, the fact that they used tools to remove the meat they needed indicates considerable complex thought. The Nature article on this find will be forthcoming.