I don’t know what I’m looking for. I suppose that I want to have a better grasp on how humans went from bands of apes to talking on the telephone.
Twas the Cenozoic Era…, (meaning the current geologic era which started 66 million years ago- when the dinosaurs died, so I should say, “Tis the Cenozoic Era” really). During the Eocene epoch, (55-35 mya), primates, similar to lemurs, emerge in the northern hemisphere during a period of global warming to secure daytime openings in the food-chain. * Then in the following epoch, the Oligocene (~35-22 mya), the presence of these prosimian primates fades in the less-forested areas throughout the world as the overall climate cooled, but they continue to exist in Africa. During the next epoch, the Miocene (23-5 mya), the climate cooled further and forests declined. At this time, monkeys spread and branched out. About 20 mya, apes evolved, first in Africa and then moving into Europe and Asia. 10-5 mya, the entire planet’s climate got cooler and drier, though not an ice age. This led to grasslands expanding, and this was generally thought to be part of why our ancestors started walking on two feet (although discoveries in the last two decades seem to contradict some of these theories).
So first there was an ancestor ape species, from which humans and chimpanzees come. To be clear, humans did not evolve from chimpanzees or bonobos. (Video of Dr. Tim White explaining that not even Darwin thought this.) The Hominia separated from this ape ancestor 7 million years ago in what is now Chad and Kenya. This separation mainly comes down to bipedal locomotion. (If you’re interested in more detail on this, and anything else related to human evolution, check out the Smithsonian’s website, particularly their interactive timeline.)
According to “Your Inner Fish: Your Inner Monkey“, by Neil Shubin, on PBS, 4.4 million years ago, Ardipithecus ramidus was the earliest known primate to stand on two feet, although they moved on four limbs when in the trees. “Ardi”, as the female fossil is referred to, stood upright at approximately four feet tall, and walked on her feet, but also had a grasping big toe for climbing in trees. The discovery of remnants of Ardi’s skeleton, in the Middle Awash region of Ethiopia in the early 1990s, by Yohannes Haile-Selassie, Tim White and collaborators, also found remains of the woodland that she lived in. (Video of Dr. White describing the discovery.) This contradicts earlier hypotheses that bipedalism developed as a result of climate change that transformed the environment from woods to savannah. Ardi was bipedal when the area was still wooded.
Ardipithecus ramidus’ canine teeth were smaller than chimpanzee’s, which are used by male chimps primarily for display, suggesting that they were not as violently competitive as chimps are.
About 3.9 million years ago, they were followed by the Australopithecus afarensis, whose footprints were discovered in volcanic ash in Kenya by the famous archaeologists, Louis and Mary Leakey. One of this species is the most famous fossil in history, Lucy.
3 million years ago, australopithecines evolved in the savanna areas of Africa, with archaeological sites in what is now Ethiopia and Tanzania. In the following millennia, they began to lose body hair and to develop full bipedalism. The climate during the Pliocene epoch became more similar to modern climates, seasonal and cooler and drier than before. The polar ice sheets formed, the Panama seaway closed, and a permanent El Niño weather pattern existed. Basically, climates began to fluctuate more radically over the millennia.
According to “Ardipithecus ramidus: Study Links Ancient Hominid to Human Lineage”, Jan 10, 2014 on Sci-News.com, “Earlier research had shown that these human peculiarities were present in the earliest known Australopithecus skulls by 3.4 million years ago. The new study expands the catalogue of anatomical similarities linking humans,Australopithecus, and Ardipithecus ramidus on the tree of life and shows that the human cranial base pattern is at least a million years older thanAustralopithecus afarensis.”
To summarize, the few fossils show a diverse group without stone tools*, with small brains, big teeth, and who were “facultative bipeds”, meaning that they could walk on two feet, but didn’t have to, like we do, aka “obligate bipeds”‘ and like later Homo erectus . (Dennell, R. The Paleolithic Settlement of Asia, 2009; and Wood, Nature magazine 2002.)
*”Wear on shaped bones from Swartkrans [South Africa] has been attributed to their use for digging, possibly in termite mounds (Backwell and d’Errico, 2001. Proceedings of the National Academy of Science USA 98(4):1358-63)” -Dennell, R. 2009: p. 17.
And now begins the Paleolithic Age:
2.5 million years ago, significant climatic changes likely led to the appearance ofhomo habilis, “handy man”. He seriously looks like a cast member from Planet of the Apes to me. They lived off of scavenging and developed the first stone tools. This is the beginning of the genus homo, with slightly larger brains and smaller jaws and teeth. For about a million years, these guys (and some ancestor species before him) had essentially the same technology of stone tools, thus this period is referred to as the Oldowan horizon.
(Source: Dennell, Robin. The Paleolithic Settlement of Asia, 2009. P. 11)
The term Oldowan comes from the site in Tanzania, Oldupai Gorge, where Louis Leakey first discovered such tools in the 1930s, one of which is now the oldest item in the British Museum (click for excellent podcast and see image below). These types of stone tools are also called Mode I by some archaeologists.
I think, looking at this rock, “How the heck is that anything special? Or in any way different from some rock I might pick up off of the ground?” Mode I tools are distinguished from just any old rock by wear patterns and edges. These tools are categorized according to their uses, such as choppers with an edge on one side, scrapers which are usually rock flakes, etc… The tools are basically made by banging one round stone, the hammer stone, down onto another, called the core rock, to produce a conchoidal fracture, a curving or arc-shaped break in the stone. The chip removed by the blow is called a flake.
Some of these tools have been found at a distance from their origin indicating that their creators and users were capable of anticipating and planning for future needs. They were also often multi-purpose. If a scraper was good for working with wood, it was probably also used for working with animal hides, etc… Recent research from UI-Chicago and UC-Berkeley has established that the various uses of the stones have left microscopic wear patterns that match those induced experimentally by cutting soft animal tissue, soft plant material, and scraping and sawing wood.
Furthermore, evidence at Kadar Gona, ca. 2.6 mya, indicates lots of “lithic litter”, meaning that hominins were discarding stones that didn’t meet standards, and were repetitively making many, precise stone tools in one location, probably because that kind of stone was preferred ( Schlick and Toth, 2006:24-5; Toth et al. 2006:215; Semaw 2006). Semaw and Toth also describe these tool makers as skillful at locating, selecting, testing, and procuring sources of high-quality, fine- grained stone for flaking (Semaw 2006; Toth et al. 2006:215). That indicates a higher level of sophistication than any modern primate has ever shown. This description also evokes the creation of culture, in which elders pass on techniques and knowledge to following generations, which chimpanzees do practice, albeit in a less complex form.
Tool use also indicates another intellectual progression, making tools for making other tools. Isaac (1986) investigated this aspect, describing how a stone might be flaked in order to create a sharp piece with which one could then sharpen a stick. This stick could then be used for digging or for stabbing small animals, as chimpanzees have recently been observed doing by Preutz and Bertolani, 2007.
It’s thought that the early Homo shifted from an omnivorous diet to carnivorous scavenging due to the Quatenary glaciation, aka the current ice age. Who knew we were in an ice age? During this period starting 2.6 million years ago, permanent ice sheets were established at the poles and this effects the climate cooling. (We are actually in the midst of an interglacial, a shorter, warmer period between glacials. The beginning of this interglacial marked the start of the Holocene epoch, about 15-10,000 years ago.) Decreasing oceanic evaporation led to a drier climate as well. It’s thought that reduced availability of delicious, sweet fruits forced some to unlock new food sources. That’s why the genus Homo posses smaller cheek teeth and jaws. Becoming more technological enables less dependency on one’s biology, and allows for the expansion of diet, both in acquisition and processing, into more higher-quality foods.
It is thought that living together in groups served a protective purpose, and aided in the processing of larger animals. Eating meat likely led to a smaller digestive tract and made more energy available for a gradually increasing sized brain.
Early hominins may have also used animal skins, ostrich eggshells – for reserving or transporting water, bones, horns, tusks, wooden branches, etc… Fire use is also debatable.
*An enormous amount of this information is from The Human Past, edited by Chris Scarre, (Wikipedia page) Second Edition, 2009. The Third Edition just came out, and I highly recommend this text from what I’ve read in the previous edition. It’s a textbook, but it’s full of illustrations and images. I’m currently through only the fourth chapter and it’s chock full of interesting information that I think every human should be familiar with. It’s the best information we have on our origins and can inform our understanding of us as animals and not-animals.
- The Human Past: World Prehistory and the Development of Human Societies. London: Thames & Hudson. 2005. (2nd edition Thames & Hudson, 2009, ISBN 978-0-500-28781-1)