Human Evolution by Dana Visalli Skull shapes & sizes: Chimpanzee, Australopithecus, Homo habilis, H. erectus, H. neanderthalensis, H. sapiens This brief rendition of the story of human evolution attempts to capture some of the highlights of the human evolutionary journey. The most important of these evolutionary highlights in terms of understanding the current human situation are 1) the natural self-centeredness that all living organisms have to some to degree, a prerequisite for survival, 2) the emergence in humans of symbolic thought (thought is in fact always symbolic, for example the word or thought tree is never actually a tree) and 3) intelligence. Unfortunately the latter two phenomena are not the same thing. Our species, Homo sapiens, is in the mammalian order called Primates, which means of the first rank, or numeral uno (there are a total of 26 mammal orders). Primates are composed of the monkeys and the apes. Both groups are characterized by having forward-facing eyes (which gives them stereoscopic vision and good depth perception, very handy when jumping 10 or 20 feet from one tree to another), grasping hands (usually with an opposable thumb), and relatively large brains compared to other vertebrates. There are over 300 species of monkeys, and only 24 species of apes, the latter made up of gibbons (17), orangutans (2), chimpazees (2), gorillas (2), and humans. The oldest primate fossils are about 60 million years old, and the lineage is thought to be somewhat older, dating to 80 million years ago. The human genetic line owes its inception to this group. Life in the trees probably initiated the characteristic larger brain and enhanced cognitive abilities of primates--by which we mean the capacity to solve problems by visualizing them rather than via autonomic genetic programming. Life in trees is three-dimensional, and so it takes more awareness of one s environment than life on the two-dimensional ground. It selected the traits that enhanced stereo vision and grasping hands, which are critical to our species, and probably bumped the functioning of the forebrain up a notch. Why did our ancestors leave the shelter of the trees 6 million years ago for a dangerous life on the savannah. Surprisingly, the current answer is climate change, which was in turn induced by plate tectonics. 40 million years ago the subcontinent of India, which had broken away from Africa long before, began to be pushed into Asia, giving rise to the Himalayas. This changed atmospheric currents and blocked moisture from falling on eastern Africa, transforming rainforest into grassland. Our ancestors did not leave the trees so much as the trees left them. Dana Visalli/dana@methownet.com/The Methow Naturalist/www.methownaturalist.com
Australopithecus, having a good day There is very little fossil evidence for the split of the human lineage (hominins) from those of gorillas and chimpanzees. Chimps and hominins split from gorillas about 8 million years ago, followed by a split from the chimp line approximately 7 million years ago. One genus of presumed human antecedents that has risen to prominence is Australopitecus (translates as southern ape ), to which the famous fossil called Lucy (discovered in 1974 in Ethiopia and dated to 3.2 million years ago) belongs, as well as the so-called Laetoli footprints found nearby by Mary Leakey in 1978. Both finds indicated that there was a hominin that by 3 million years ago had the skeletal structure that allowed it to walk completely upright. However the brain size of the Australopithecines was just barely larger than the brain of a chimpanzee. The paleoanthropologists like to say that hominins stood up first, and got smart later. Survival must have been challenging for the likes of Australopithecus afarensis, because they had given up the refuge of the trees but had no way to protect themselves against the numerous predators, especially lions and other wild cats, that frequented the savanna. They were incapable of utilizing either fire or weapons; one Australopithecus skull has been found in a cave with leopard canine teeth puncture marks in it. Another informational find is a red pebble in an Australopithicene cave dated to 3 million years ago. The little rock is known as the Makapansgat pebble; it has natural pockmarks on it that make it look like a human face. The rock type of the pebble is unknown in the immediate area, and must therefore have been carried into the cave, probably by an Australopithecus who recognized the hominid resemblance. It would take symbolic thought to execute such an action; no dog or cat or chimpanzee has ever brought a rock home because they thought it looked like them. It is considered to be the first sign of symbolic thought in the history of our evolutionary line. One of the Australopithecines evolved into the first species in our genus just over 2 million years ago, Homo habilis (homo means man or human and habilis means handy ). Chimpanzees have a brain case capacity of about 400 cm3; Australopithecines have about 500 cm3, and H. habilis checks in at approximately 600 cm3; so the brain was growing over time. The reason is probably that the latter two creatures were able to scavenge meat. Australopithecus would have been able to use sticks and stones to chase predators off of kills, and H. habilis was able to make stone tools. They were clearly not able to fully defend themselves though, as ample fossil evidence indicates that H. habilis was a staple in the diet of large predator cats. H. habilis appears to have persisted until 1.4 million years ago, when a larger brained (1000 cm3), larger-bodied hominid, Homo erectus ( upright human ), becomes dominant (there is some overlap in the presence of the two species). It first appears in the fossil record 2 million years ago, and seems to have migrated out of Africa as far east as Indonesia and Vietnam by 1.5 million years ago. A H. erectus skull found in Dmanisi, Dmanisi Man, a H. erectus that lived on after losing his teeth
Artist s concept of Homo erectus taming fire Georgia dated at 1.8 million years had not only lost its teeth while it was alive, but bone had grown into the teeth sockets. Thought to belong to an old man of 40 years, such a toothless creature would have no way of surviving without the daily support of his clan, possibly even to the point of pre-chewing food for him. This is taken as the first evidence of loving care and compassion among hominids in the fossil record. It appears likely that H. erectus tamed and utilized fire as long as 1.4 million years ago. Fire would have made all the difference on the trail to modern humans, as it made the nights safe from predators, made body hair unnecessary, allowed its masters to cook food and thereby both chew less and obtain far more nutrition from both animal and plant food. Both the gut and the lower jaw could recede as they did not need to work so hard, making more energy available to other parts of the body--like the brain. H. erectus also improved on the tools of H. habilis, although the degree of improvement was greater in Africa and not particularly pronounced in Asia. It is not known to what degree H. erectus could communicate through speech, but some workers think that fossil evidence reflect vocal capabilities within the range of H. sapiens. The species persisted for over a million years, with some dating the last fossils to be only 50,000 years old, in China. The dominant story at present is that about 2 million years ago H. erectus migrated out of Africa, the first hominin to do so. Outside of Africa it remained H. erectus, while inside of Africa the evolutionary pressures of an increasing population of multiple Homo species led to the emergence of one that became our immediate ancestor, Homo heidelbergensis. This is curious German name for an African species, but so it goes. Its brain was just about as large as our own. 400,000 years ago some heidelbergensis migrated out of Africa and apparently turned left instead of right, straight into the Pleistocene Ice Ages in Europe, where it was transformed over time into the Neanderthals (Homo neanderthalensis). Others of the species remained in Africa and evolved into Homo sapiens, which then first left Africa 70,000 years ago (this date is hotly contested), encountering the Neanderthals in Europe upon arrival there 40,000 years ago, and possibly H. erectus in Asia. Neanderthals seem to have existed from about 300,000 years ago to perhaps as recently as 25,000 years ago (again, dates are uncertain). While they are best known as inhabiting Europe, which has had the most paleontological work, they populated a large swath of Eurasia extending from Britain in the west to Kazakhstan and Russia in the East. Two aspects of the Neanderthals stand out. One is that they had a brain slightly larger than our own species, about 1400 cm3 as opposed to our own average of 1250 cm3. They clearly had some smarts, being as especially forebrain size is strongly associated with cultural learning and behaviors that are relatively independent of genetic programming. On the other hand, their cultural expression and tool making abilities changed very little over their almost 300,000 existence. One paleontologist described their tool making as brilliant, but stupid, because it was well done but never changed. A likely reason for this is that they probably lived in isolated clans and with relatively low population numbers, so there was little opportunity for extended cultural learning. Neanderthals did create a complex culture indicative of bountiful symbolic thought. They were known to build dwellings out of animal bones (and presumably animal skins) and to construct water craft. Neanderthal tools (known as Mousterian tools) as old as 170,000 years are found on islands throughout the Mediterranean. There is some evidence that they buried their dead in a symbolic way, and even that they made beer! Recent artists renderings of Neanderthals show them as much more intelligent and modern human-like than previously.
The 40,000 year-old Venus of Hohle Fels Our species seems to have left Africa about 125,000 years ago, migrating into the Near East (Syria and Palestine). There was probably competition with Neanderthals at this time, and this first out of Africa population of modern humans appears to have died out rather quickly. About 70,000 years ago modern humans left Africa by crossing from what is now Ethiopia to today s Yemen, and thence spreading around the world. They reached Australia by 46,000 years ago, Europe by 43,000 years ago, and traveled to Alaska via the Bering Land Bridge (now submerged under the Bering Sea) about 20,000 years ago (all dates are uncertain). The oldest DNA evidence of human habitation in the lower 48 is fossilized human coprolites (feces) found in the Paisley Caves in southcentral Oregon. Mysteriously, there is a modern human site now accepted in Chile called Monte Verde that is dated to 14,800 years old. Interestingly Homo sapiens, which first appeared in Africa about 250,000 years ago, showed the same slow cultural development as did Neanderthals ( brilliant but stupid ) until perhaps 50,000 years ago, when there then began something of a creative explosion. There is some minimal evidence of symbolic art created by modern humans in Africa dating to 150,000 years ago, but evidence of an expressive explosion dates to Europe starting 40,000 years ago. 40,000 year-old cave art in Indonesia The first known symbolic expression or art by Homo sapiens is found in caves on the coast in South Africa, with quantities of ochre presumably used for body painting dating to 165,000 years ago have been found, and pierced shells for beads are dated at 100,000 years. The oldest undisputed work of figurine art is the Venus of Hohle Fels, found in a cave in Germany and dating to 40,000 years ago. It depicts a exaggeratedly reproductive female, and no doubt was associated with human fertility and reproduction. The earliest cave paintings are newly dated images on the wall of a cave in Sulewesi, Indonesia, also dated at 40,000 years. There is open air Paleolithic art on rock walls in Europe dating to 40,000 years ago, and cave painting seems to have been initiated there soon after. Agriculture arose independently in three core areas of the world southwest Asia, China and Mesoamerica. The fact that it arose independently on different continents suggest there is natural trajectory for humanity in that direction. By 7500 BCE one of the first known agricultural villages, Jarmo, had emerged in northern Iraq. Jarmo was a collection of about 25 houses, the inhabitants of which depended on a system of mixed farming and husbandry. They grew domesticated barley, emmer and peas combined with herding sheep and goats, while hunting provided only about 5% of their total food. A 35,000 year-old panel of horses in Chavet Cave, France
Agriculture did not evolve because it is an easier option than hunting and gathering. It requires far more effort in clearing land, sowing, tending and harvesting crops and in looking after domesticated animals. It does not necessarily provide more nutritious food. The one advantage agriculture has over other forms of existence is that in return for a greater degree of effort it can provide more food from a smaller area of land. The explanation for the appearance of agriculture that best fits modern knowledge is based on increasing population pressure. The population of the world 10,000 years ago was about four million, rising to about five million by 7000 years ago. It then began doubling every millennium, to reach 50 million by 1000 BCE and 200 million by 0 CE. The upward trend has continued every since, so that agriculture today supports a world population of over seven billion. The adoption of agriculture was the second most fundamental change in human history, after the psychological journey into symbolic thought. Hunting and gathering societies were essentially egalitarian (except when they had abundant food, see for example the story of Sungir in Russia, a 28,000 year old hunting society with all the mammoth meat they could eat and a very hierarchical social structure). Sedentary communities, almost from the beginning, resulted in increased specialization and the emergence of religious, political and military elites with the power to direct the rest of society. Genetic proclivities seem to harness the mind to fabricate an abstract set of beliefs for the purpose of of unifying individuals ensured obedience to group leaders and group values. Agriculture also gave rise to the concepts of property and ownership. All organisms are genetically programmed to favor themselves, their own survival and reproduction. This is evident in the names groups of people give themselves; for example the word Inuit means human beings, Dine (the Navajo) means the people, Ani-Yunwiya (the Cherokee name for themselves) means the principal people. The word Mediterranean means the center of the Earth, which is where the Mediterraneans imagined themselves to be, because of biological programming. A brief glance of U.S. history shows us that both South Korea and Vietnam declared independence in September of 1945, and the U.S. went to war in both instances to prevent natives who lived 6000 miles from our shores from exercising their own will, because we are the people and they are something less than that. In both instances wars resulted that killed 3-4 million of the local population. More recently another 3 million have been killed in Iraq by U.S. violence. But all humans are programmed to submit to authority and the people who inhabit North America are equally subject to this pre-programmed behavior. It is because of this that almost no one speaks out or acts out against the institutionalized murder of other human beings. The plasticity of human behavior and the specie s unprecedented ability to learn new behaviors suggests we can to some degree choose modes of existence that are adaptive and functional. We are more controlled by our genes than we have realized, and so it would seem that the more we discover about the mechanisms of genetically controlled behavior, the more possible it will become to transcend these controls through awareness and conscious choice. We may then in the words of A. Rosenfeld, "for the first time in our history, work for ourselves instead of for our genes, exercise truly free will and free choice, give free rein to our minds and spirits, attain something close to our full humanhood.'' Let My Country Awake Rabindranath Tagore Where the mind is without fear and the head is held high, Where knowledge is free, Where the world has not been broken up into fragments by narrow domestic walls, Where words come out from the depth of truth, Where tireless striving stretches its arms towards perfection, Where the clear stream of reason has not lost its way into the dreary desert sand of dead habit, Where the mind is led forward into ever-widening thought and action, Into that heaven of freedom let my country awake. Dana Visalli/dana@methownet.com/The Methow Naturalist/www.methownaturalist.com