Growing up, we were taught about our relation to other primates, monkeys, gorillas, chimps etc. As children, we can see the visible similarities, their hands, noses, and body shape. The story behind how were connected to them is where things went way over our heads. This week’s lectures were so interesting to me, as someone who has always loved animals and especially primates, it was so compelling to learn more about our ancestors. Paleontologists and biologists and anthropologists and others alike use fossils and dating to try to align our history and relation to early hominins. Hominins are early primates that have traits that lead us to believe they have a connection to humans, either that they lead to the development of the modern human or that they were related to them and died off. There are many defining traits that separate us from what we know as primates. 

The first and most obvious trait is that we walk on two feet, also called being bipedal. Although gorillas and other primates can walk on two feet, it is not their primary mode of locomotion. Because many of the primitive primates died millions of years ago, the only way we can observe them is through fossils and remains. In order to determine if a fossil or skeleton was bipedal they look at the skull first. The foramen magnum is a hole in the skull that the spinal cord enters through to connect to the brain. When a species walks on all fours, the foramen magnum is more on the back of the head whereas bipedal species have the foramen towards the bottom of the skull, this suggests that the rest of the body is below the head rather than behind. Another big factor in determining if the species was bipedal is the leg bone morphology. The femur is the bone between the hip and the knee and with bipedal animals, the femur is larger and stronger because it is meant to support the body when alternating legs while walking. This has been a characteristic that separates us from all other animal species. 

Another, less obvious, trait is our tooth morphology. We have larger cusped molars for chewing and grinding with much smaller canines. The canine teeth in primates were primarily for fighting rather than for predatory reasons. Our ancestors had much larger canines than we have nowadays. Australopithecus afarensis were our first ancestors to have smaller canines compared to molar and incisor size, showing a diverse diet. The Australopithecus garhi are thought to branch off from the afarensis. They had very similar teeth to us along with their leg to arm ratio also similar to us. The sagittal crest is a bone growth along the top of the skull that connects to the mandible with muscle for very strong chewing, this is something very obvious in pictures and something us humans lack. Although most of our primate ancestors have been extinct for quite some time, we’ve been able to learn a great amount from their fossilized bones. We know that the first rudimentary tools were used about 2.5 million years ago by the Australopithecus garhi. This gives us great insight into when the brain began developing into what we know as our complex problem solving brains.