You know what, I am feeling generous, so you folks get a two-fer today! (Plus I am well into the future parts of this series, and really want to move things along!)
The Ape-Descendants (1)
It would be too much for me to detail the long history of life on Earth, over the billions of years from the first organisms to now. Such a topic is way too complex for a simple blog series such as this one. Suffice to say, that over much of the history of this planet, organisms have grown and thrived. Many of these were simple organisms, single cellular, but over time new and diverse forms of life came to inhabit Earth. Plants, animals, trilobites, dinosaurs, and eventually mammals and primates. It was from the latter that our own ancestral lines started to evolve and diverge, and about 8 million or so years ago, the earliest members of our ancestors start to appear in the fossil record.
Our story starts with those that are called the Pre-Australopithecines. In the book by Larsen, he highlights the finds of two fossils, one from Sahelanthropus tchadensis which was found in modern day Chad, and which dates from 7 – 6 million years ago. The brain was small, and much more like that of apes. That being said, it did have a couple of traits that have more in common with more modern hominids. First, it is likely that it was bidpedal, walking upright just like ourselves. Second, it had non-honing teeth. Whereas apes have teeth that have a habit of sharpening themselves, this first fossil did not, which is a characteristics of our own teeth. Several of the remains found with this fossil indicated it lived in a forest by a lake.
The other fossil found in Kenya, Orrogin tugensis, has been dated to about 6 million years ago. The remains of several different skeletons were found, most of which have indications of early traits of our own species, but also some that are reminiscent of apes. Several partial femurs indicate bipedalism, and the canines were once again non-honing. However, a hand phalanx had traits like those of apes, a curvature typical of those apes that live in trees. The indication too, that this creature evolved in a forest setting.
There were also fossils found in Ethiopia, Ardipithicus kadabba and Ardipithicus ramadis, both of which were found in an area were many other important fossils have been found, and have contributed to our knowledge of early hominid ancestry. These two fossils date from about 6 million years ago to about 4.5 million years ago. Just like the two earlier fossils, these two also showed mixed characteristics of both hominids and apes. Their fossils indicated bipedalism, and non-honing chewing, but also plenty of ape like traits that indicate a life in a forest setting.
As we move through time from about 4 million years ago, to about 1 million years ago we come across the Australopithecines, represented by hundreds of fossils spread across at least seven different species, all of which belong to the genus Australopithecus. I will not take the space to detail all these fossils, as there is plenty other of material out there for those that are interested.
However, in general as we move through time from 8 millions years ago, to about 1 million years ago, there is evidence of several changes moving through the fossil records. Brains increase in size slightly as we get closer to Homo. In addition, bone move away from more ape-like traits, towards those we see in our modern species. In addition, the teeth of our ancestors lose the honing trait that is present in apes.
Many of the same trends continue as we move from the Australopithecines to the earliest members of genus Homo. Our brains continue to increase in size, and overall the size of our faces and teeth shrink. By the time we come to about 2.5 million years ago, the first of our own genus has appeared side by side the Australopithecines, and which shares many of the same traits as those early fossils. The name of this being was Homo habilis and it was the first species in our ancestral lineage.
Homo habilis is the first hominid species associated with the use of stone tools, the so called Oldowan Complex stone tool culture, though it is possible that the contemporary species, Australopithecus ghari may have also used the stone tools. As such A. ghari is often seen as the ancestor to Homo habilis and the bridge between the early Australopithecines and the genus Homo.
Homo habilis in turn gave rise to Homo erectus, and this is where our ancestry gets really interesting. For in Homo erectus we see the first globalization of our species, as it is the first of Homo to leave its cradle in Africa, and spread across the planet. As we move closer to our own modern species, we see a continued decrease in the size of our teeth, face and jaws. Our brains continued to increase in size, as did the browridge on our skulls. There is also a generalized overall increase in our body size, the lengthening of our legs and height. Between 2.5 and 1 million years ago, stone use continued to grow and develop, and we also see the first controlled use of fire. The development of fire only aided early humans in the expansion across the globe. And it was from Homo erectus that our own modern species would evolve.
But I want to stop here. I know that this post might be a little more dull. There have been entire books written about the development and evolution of our species, and I have only recounted the smallest selection of that here. I don’t want to go on and on with endless listings of fossils and species, because that is not the point of this post. There are some resources below, and I can always provide more if you want to read more about all these topics.
The point is, in these earliest fossils we can see very distant branches of my own family tree. It is amazing to think that in the hills and valleys of Africa, are the fossils of beings to which I am related. In the shape of my skull, the size of my brain, and the hands with which I am typing, all of those things connect me back to those earliest times. I wonder if I would still be able to type this if my hands were still curved, likes those of apes? I mean, I have seen apes type just fine, but it is something that is amazing to think about.
Plus, through all the literature and artist renderings, I can kind of understand what life might have been like for the earliest of hominid ancestors. In some way, I can almost reach out and touch them. That is what all the research is about, that is what this series is about. It is about reaching out to my ancestors, and remembering them. It is about telling their stories and bridging the gap between our world and theirs. It is about learning from them, and that even after millions of years, we still carry them with us.
In our thoughts, in our blood, in our bones, and in our hearts.
So far, I have really just been “setting the stage”, so to speak. In the next chapter, we really get into the meat of this series. I will be talking more about Homo erectus, and of course, neanderthals and modern humans. That will be where my own story starts to unfold.
Thanks for reading!
1) This is more of a pun, inspired by The Hitchhiker’s Guide to the Galaxy. In reality, apes and men are more like “cousins”, as we share a common ancestry.
Essentials of Physical Anthropology: Discovering our Origins. By Clark Spencer Larsen