Of the two species of Early HomoHomo habilis is the favored ancestor of Homo ergaster and all subsequent hominin species. While the origin of Homo habilis has been in a state of flux in recent years, the discovery of Au.
The discovery of Lucy in the early s led some researchers to turn away from Au. In recent years, the idea that a cladistic event had occurred with Au. There are proponents in support of each of the evolutionary scenarios, with their share of pros and cons.
Louis and Mary Leakey discovered the first fossil material in at their site in Olduvai Gorge, Tanzania. Louis had been recovering stone tools from the site for years, but the manufacturer of those tools had previously eluded him. Their skull, face, Homo lad ready to open his face gap wide dentition were more gracile than the australopiths. Their teeth and dental arcades were very human-like.
The skull base was flexed, as seen in Au. Cranial capacity ranged from to cc with a mean of cc. This gave them an EQ of 3. At this point in hominin evolutionary history, we see increased asymmetry in the two hemispheres of the brain, termed lateralization or left hemispheric dominance.
The left side of our brain is involved with language and analytical processes. Like all Old World monkeys and apes, H. They thus had the neural capacity for language. The left hemisphere is also related to right-handedness.
They may have exhibited our tendency to hold objects with our left hand while working on them with our right. The frontal lobe, important in association processes, was expanded and resulted in more of a vertical forehead. The enlarged brain may have been facilitated by a decrease in gut volume, combined with a higher-quality diet that resulted from increased cognitive capabilities and an expanded technology base.
The mandible was more gracile, reflecting their reduced masticatory capabilities. Like the majority of the australopiths, H. While the digits were still curved, they had increased gripping capabilities for tool manufacture and use, as evidenced by the pronounced attachment site for the flexor pollicis longus muscle, which acts to flex the thumb.
The femoral head was enlarged and the neck shortened. Those changes are thought to have been the result of increased strain generated by an expanded pelvis for birthing larger-brained infants. However, no fossilized pelvic fossils have been found. Their foot was more modern, in that the hallux was no longer divergent but rather aligned with the lateral four digits, and the toes were shorter.
They had less mobility in their feet, in that the foot had become more of a support structure like our own. The metatarsals were thick relative to modern feet, and the morphology of the third metatarsal suggests that they did not yet exhibit the degree of weight transfer and propulsive capabilities seen in modern humans. Certainly one of the most interesting things about H. The cultural period at that time, and extending through Homo erectusis termed the Early Paleolithicor the early portion of the Old Stone Age.
While other species apparently preceded H. The technique involved the selection of a cobble a workable-sized rockfollowed by the use of a hammerstone to remove the outer rough surface see Figure The flakes that are removed may be suitable for cutting and slicing. The process is called hard percussion, and the shaping is known as lithic reduction. Stone resources for the manufacture of tools were chosen for their suitability and transported across the landscape.
Of course, this indicates a level of cognitive complexity, but we must remember that chimps and orangutans choose sticks and grass of particular widths and strengths, trim them to the appropriate length, and transport them in their mouths to their site of intended use. Apes learn by trial and error, innovation and imitation, and cultural transmission, i. Cultural transmission of innovations is even seen in monkeys, e.
Japanese macaques washing sweet potatoes, skimming grain kernels floating on the surface to separate them from beach sand, and bathing in volcanic springs.
While we do not know which species was the first to invent stone tools that were modified from their original form via lithic reduction and shaping, we can see the precursors of innovation and cultural transmission in our primate relatives. The real skill comes with having the manual dexterity to do so, making a tool that can accomplish a variety of uses, and the ability to teach others. There is only one example of teaching in nonhuman primates and that was a mother Homo lad ready to open his face gap wide in the Tai Forest of the Ivory Coast that helped her daughter crack a nut, using their unique hammer and anvil technique.
Our closest relatives, with all of their intelligence, symbolic capabilities as demonstrated in language studies, and similarities to our own behavior, do not know enough to teach their children. We go on and on about encephalization in the hominin lineage and technological advancements in the archaeological record over time, but what may have been the true dividing line between ourselves and the apes, whether bipeds or not, was the ability to teach our young, kin, and other group members and thus increase their chance of survival.
The vehicle for developing a theory of mind is language. Human children develop a theory of mind at three or four years of age.
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Prior to that time, they do not realize that they or others may have incomplete information. Here is a fun anecdotal account that I always relay to my students:.
My brother Michael was visiting my brother Jimmy. He helped Michael find everything that he needed to clean the baby. This indicates that my nephew had not developed a theory of mind. He did not understand that Michael did not know things that he knew. They thus may have had the motor control that allowed more lingual activity and the ability to comprehend the resulting sounds they could produce.
Great apes can comprehend symbols, i.
They have been taught American Sign Language, various computer languages, and spoken language. Where they fall short is in syntax—they cannot string together symbols into meaningful sentences. I firmly believe that the descendant species of Early Homoi.
Homo ergasterhad theory of mind, based on their stereotypical production of tools. There had to be teaching, learning, and training involved in order to produce an implement that is readily recognized as an Acheulian hand axe see Figure Thus, since we see an earlier stage of tool production in Early HomoI would argue that they had rudimentary language and theory of mind.
The Oldowan tradition lasted from approximately 2. Tools consisted of crude choppers see Figure In addition, there is evidence of possible wooden digging sticks or spears at the site of Koobi Fora, in the East Lake Turkana region of Homo lad ready to open his face gap wide and possible bone tools at Olduvai Gorge. Tools were likely used for acquiring and processing both animal scavenging, butchering, disarticulation, skinning, cutting flesh, chopping bones open, etc.