About 1.8 million years ago Homo erectus, one of the better known ancestors of humans, emerged and developed what is known as the Acheulean tool tradition. Although Homo erectus had a cranial capacity close to the lower range of modern human and may have had many human-like social characteristics, the tools never become more complex than simple scrapers, choppers, and stone axes. They change little over the next million and a half years.
Mozart wrote his symphony No. 41 in about two weeks from late July to early August in 1788. Sir George Grove declared it “the greatest orchestral work of the world which preceded the French Revolution.” The symphony, nicknamed the Jupiter symphony, was his last symphonic work and one of three symphonies composed in a short time frame in the summer of that year. The full arrangement has parts for eight instruments and spans over a hundred pages.
How did we get from Homo erectus to Mozart?
The development of humans began about 7 million ago when the human branch of apes speciated from chimpanzees. These very early ancestors probably had some bipedal capability but may have still spent much of their life in trees. Their brain capacities were similar to many modern apes. As the African climate changed to create the savannas of Eastern Africa, these ancestors moved into the plains gradually developing more ability to walk on two legs and larger brains. (1) The famous Lucy skeleton dated to about 3 million years ago represented a species that walked upright but probably ate grasses and leaves. (2) About 2.5 million years ago, the genus Homo appears with significantly larger brains. Homo erectus had a typical cranial capacity about 75% of the average human. These early ancestors began to eat meat probably scavenged at first and the later hunted. British primatologist Richard Wrangham argues that Homo erectus with its mastery of fire first began to cook food. Cooking food makes nutrients more assimilable. Quite likely both meat and vegetables were cooked. Homo sapiens most likely evolved from Homo erectus from some common ancestor with Neanderthals through several intermediary species.
Anatomically modern humans begin to appear in the fossil record about 200,000 years ago and some evidence of culture, such things as body decoration and burial practices, appear in the record by 160,000 years ago. There is a chance that the beginnings of human culture extend much further back than that but the evidence has been lost or is yet undiscovered.
Were these early humans from 200,000 years ago truly human even though they may have had all of the appearance and brain size of contemporary humans?
Unfortunately we have really little to go on to understand what these humans were like. The fossil record is very fragmentary from this period so quite possibly significant evidence of culture has been lost. Jewelry and clothes made from perishable material would not survive from this time. We can have no idea whether these humans spoke language as we speak today. While they likely communicated in a sophisticated manner with sounds and gestures whether their language had the ability to express abstract or complex thoughts is completely unknown.
I think, however, we have some tantalizing clues that these early humans were not like us in many significant ways.
We have the lack of evidence of significant cultural development during the Eemian interglacial. Interglacials are warm periods sandwiched between colder periods when the ice sheets grow and advance. Modern humans developed agriculture, domesticated animals, and created settlements with relatively large populations during the Holocene interglacial that began about 12,000 years ago. The Eemian interglacial which was very similar was from 130,000 years ago to 114,000 years ago. Why didn’t humans at that time do what humans did during the Holocene? Presumably even a small population of humans with modern capabilities would have flourished in the climate of the Eemian and created large settlements.
Beyond that, we have some fairly consistent genetic, linguistic, and archeological evidence that points to Southern Africa as the origin of modern human capabilities about 100,000 years ago.
A Tishkoff, et al. 2009 study concludes that “the people who today hold the most diverse genetic structure in the world are the San bushmen of South Africa. Thus, the San are likely to be the descendants of the first group who stayed behind, the first group of humans who colonized Africa and then the rest of the world.” (3)
We have archeological evidence pointing to the same general region. At the Howiesons Poort and Stillbay sites in South Africa are found “lithic stone industries that are comparable to European Upper Paleolithic in their sophistication, yet they date fully 20,000 to 30,000 years earlier.” (5) The dates for this are 70-77,000 years before present and predate significant human migration from Africa. There is also evidence of artistic workshops from Blombos Cave in South Africa from as long as 100,000 years ago.
Linguistic evidence, while more controversial and subject to criticism, also supports a South African origin of language. Analysis of the number of phonemes used by language shows a clear pattern of less phonemes in use in languages the greater the distance from Africa. San bushmen use over 200 phonemes. English uses 45. Hawaiian has only 13. Quentin Atkinson states : “An origin of modern languages predating the African exodus 50,000 to 70,000 years ago puts complex language alongside the earliest archaeological evidence of symbolic culture in Africa 80,000 to 160,000 years ago. Truly modern language, akin to languages spoken today, may thus have been the key cultural innovation that allowed the emergence of these and other hallmarks of behavioral modernity and ultimately led to our colonization of the globe.” (4)
So what to make of all of this? What follows is speculation.
It is what I call the “Revenge of the Nerds” theory.
Anatomically modern humans appeared in Africa about 200,000 years ago but these first humans were still lacking significant cognitive abilities possessed by modern humans. They probably did not have a language capable of abstract thought. Behaviorally they may have similar to super-intelligent wolves living in small bands with cooperative hunting, food gathering, and child rearing. There were probably multiple sub-populations of this early human. Some groups died out. Groups split off and became separated. Other groups were successful in various ways. At some point a group moved into Southern Africa. This group may have been physically weaker, less violent, and more intelligent to begin with and may have been actually forced into a more marginal area through competition with other physically stronger or more violent groups. In other words, we became human perhaps because we were weaker and had to find a way to make in living in a marginal environment.
We had to find ways to live with our intelligence and through greater cooperation in larger groups. We gave up our small bands for extended families. This not only increased the likelihood of children surviving to adulthood but also, through reciprocal trade, the chances that one family could survive tough times by calling on the larger extended family. From this sub-population emerged the critical genetic traits that resulted in a rewiring of human neurological system leading to language and culture as we know it. Although these changes may have begun at an earlier time, about 100,000 years ago this new human would become established in sufficient numbers that it could make significant advances that would allow it eventually to out compete the other sub populations and displace them (revenge of the nerds?).
Whatever this rewiring was, it was not a larger brain. First, brain size increase had already plateaued in our evolutionary history by this time. Additionally, brain size in general is probably vastly overrated. There have numerous cases of large sections of the brain being removed in children who then go on to lead mostly normal lives with no diminution in language or intellectual ability. Furthermore, the range in brain size in even normal humans is fairly wide. A study of 46 adults found the brains of men ranging from 1052.9 to 1498.5cc in volume and women ranging from 974.9 to 1398.1cc. (6) There seems to be little or very small correlation of brain size with intelligence.
When these new humans initially began to develop the capabilities for creating culture, quite probably the initial advantages were small. The appearance of the advanced abilities for language, art, and symbolic expression in some individuals would carry little advantage to humans as a whole unless there was a critical mass of humans with like ability. You can’t have culture without sharing it with others. So this capacity may have progressed slowly at first. Once, however, a critical mass was reached, the spread of the genetic capabilities for culture was somewhat like a snow ball becoming larger and larger as it rolls down the hill. This is why the development of larger groups and extended families is so important. Without the larger groups, any developing cultural advantage would die out for lack of sufficient numbers of others to share with. The neurological changes must have involved selection for intelligence, language ability, reduced aggression (or at least sublimated aggression), and increased capacity for cooperation. All of these things would be needed for humans to make the transition to cities and civilizations later in the Holocene and they were probably not present during the Eemian in any population of sufficient numbers to do the same.
What drove the evolution of this new human was a feedback process between some new neural complexity and an expanding capability for communication. By communication, I mean not just language but the entire range of human communication including art, music, myth, and the entire social framework that makes us human. I already mentioned the evidence of artistic workshops from Blombos Cave. During this time most likely the shaman makes his appearance on the human stage. Through evidence is still lacking, due to weathering and perhaps over-writing of preexisting patterns, eventually evidence of shamanic practice in rock drawings dating from these times may be found. We can only guess about language, myth, and music.
The actual physiology of the neurological changes involved in the development of this new human will always be somewhat obscure. We will never be able to open up the skull of a human from 200,000 years ago and compare the brain to that of a contemporary human. Most likely there were multiple changes and transformations in the brain architecture and we can only get a glimmer into what some of them might be.
One might be tempted to believe is that these changes were, at least in part, involved with the specialization of brain functions in the hemispheres. As most people know from references in popular culture, the brain is divided into two hemispheres: the left and right brains. Language is associated in most people with the left brain whereas visual perception and artistic ability are linked to the right brain. Autism with its deficiencies in language and social skills has been associated in some cases with lesions on the left brain. Perhaps the early human simply lacked the development of various structures and capabilities in the left brain and the new human developed these structures that enabled us to take the next step in our development.
Unfortunately, if there is any truth to this theory, it is almost certain that the story is much more complicated. The associations of language with the left brain and of artistic and perceptual abilities with the right brain are only a tendencies. Some people have the associations reversed and others seems to share language processing across both hemispheres. Other studies have shown that the right brain itself seems to have some language processing capability. Some people who have had sections of the left hemisphere associated with speech (Broca’s area) removed still seem to have language abilities. Making the issue more complicated is that this same lateralization of function seems to exist in other mammals, including apes, and may also have a long evolutionary history in the human line with evidence of handedness in hominid tool making. So the history of this specialization of brain function must go much farther back in time than the last 100,000 years.
With the above caveats in mind, let’s look at the Dopaminergic Mind hypothesis of Frank Previc. (7) Previc argues for increased levels of dopamine in the left brain as the key development in human brain evolution. Dopamine is a neurotransmitter. Neurotransmitters are chemicals in the neural system that enable signals to be transmitted. There are many neurotransmitters but perhaps the most important are dopamine that predominates in the left hemisphere and serotonin that predominates in the right hemisphere. Previc believes high levels of dopamine production to be associated with higher intelligence in other species, including apes, parrots, and dolphins. Intellectual deficits, such as autism, are associated with reduced dopamine levels. Dopamine is the key driver of the reward system. The dopaminergic personality is goal-oriented with a focus on the future. It is characterized by high intelligence and creativity. Previc thinks that the change to higher dopamine production began long go with Homo habilis with the initial consumption of meat, but he identifies a period about 80,000 years ago where additional changes occurred and dopamine production reached new levels. Dopamine, we might note, plays a key role in the body’s ability to cool itself in part by triggering sweating. This raises the possibility that the additional dopamine production might have selected initially for the advantages it conferred for the survival of a relatively weak creature whose most outstanding physical ability is its capacity to cover long distances in high temperatures without overheating.
Dopamine, as explained, is a neurotransmitter. As such, it is a facilitator of messaging in the brain. Is it possible that simply by increasing levels of neurotransmitters in an already large brain we can explain the changes of 100,000 years ago? Or were other additional changes in neurological structure required? Was increased dopamine necessary but not sufficient by itself to bring about the evolutionary changes in the brain?
An interesting clue comes from mirror neurons. Mirror neurons are neurons that fire when we take some action and also when we see others take the same action. They have been found in humans and chimpanzees. In other words, if I pick up an apple to eat or I see you pick up an apple to eat, the same set of neurons fire. V.S. Ramachandran writing in 2000 thought that the discovery of mirror neurons was the important unpublicized story of the decade. (8)
Ramachandran argues that mirror neurons are what set the stage for the human capacity for language and culture:
“Mirror neurons can also enable you to imitate the movements of others thereby setting the stage for the complex Lamarckian or cultural inheritance that characterizes our species and liberates us from the constraints of a purely gene based evolution. Moreover, as Rizzolati has noted, these neurons may also enable you to mime — and possibly understand — the lip and tongue movements of others which, in turn, could provide the opportunity for language to evolve. (This is why, when you stick your tongue out at a new-born baby it will reciprocate! How ironic and poignant that this little gesture encapsulates a half a million years of primate brain evolution.) Once you have these two abilities in place the ability to read someone’s intentions and the ability to mime their vocalizations then you have set in motion the evolution of language. You need no longer speak of a unique language organ and the problem doesn’t seem quite so mysterious any more.” (9)
It is not difficult to see how mirror neurons might be involved in triggering some increased capacity to rehearse future actions and events in our minds. Mirror neurons might also be a key element in the sense of the body double that occurs in out-of-body and near-death experiences. As such, these could be directly related to religious beliefs in life after death and the animistic beliefs of spirit.
Several researcher have cast doubt on whether mirror neurons represent a distinct type of neuron. One theory is that mirror neurons are just ordinary neurons trained by associative learning. Even if that is the case, however, that does not invalidate the idea that the operation of mirror neurons may be critical to human evolution. Ramachandran admits that mirror neurons by themselves were probably not sufficient to trigger the evolutionary leap that may have happened about 100,000 years ago. Perhaps Previc’s theory of increased dopamine production led to additional capability by increasing of learning speed that is accomplished by mirror neurons. It might also be the increases in the white matter of the brain, the material is essential for carrying nerve impulses between neurons, played a key role in enabling the mirror neurons to work more quickly and efficiently.
Two underground theories favored by New Agers deserve some mention. One theory promulgated by Terrence McKenna says that the consumption of hallucinogens, primarily mushrooms, somehow triggered key changes in human brain and led to the increase in brain size. Another theory by Tony Wright and Graham Gynn claims that consumption of fruit in the jungle was the key evolutionary influence that triggered our brain growth and that in the last 200,000 years our brain growth has stagnated because we have forsaken the fruit diet. According to this theory, this has resulted in, among other things, an abnormal dominance by our left brain. Ironically some of the same people argue in favor of both theories even though they are clearly contradictory in many respects.
McKenna, at least, gets the key events in evolutionary history right by pointing to our departure from the jungle and emergence on the plains where the mushrooms could be found. Wright and Gynn have to argue that the original humans remained behind in the jungle, where they for some reason became bipedal, loss their hair, and developed sweat glands, only to emerge 200,000 year ago, apparently in a mass exodus, since the only exclusively fruit eating apes found the jungle today are not human, after which they then began eating meat and other plants. Ultimately there seems to be very little evidence in favor of either theory. Wright and Gynn have to argue against practically the entire archaeological record for their theory to be true. And anyone who has looked for mushrooms of any sort would know that finding them is somewhat hit-or-miss, seasonal affair so it would be difficult to believe that even if hallucinogenic mushrooms were consumed on occasion by pre-humans that they would be able to exert any continuous influence on human evolution.
Although I think McKenna’s theory as stated is wrong, McKenna might have brushed upon something that might be related to the changes that occurred about 100,000 years ago. Intriguingly hallucinogens resemble chemically either dopamine (the phenethylamine class such as mescaline) or serotonin (the tryptamines such as psilocybin and DMT). Hallucinogens disrupt the actions of serotonin and change the actions dopamine which seem to be linked in action in the brain. What is more interesting to hypothesize is that our historical, long-term usage of hallucinogens is in somehow related to these transformation in our neurological structure that occurred about 100,00 years ago. There is also the possibility that the shaman with an ability to exploit these brain chemicals either through deliberate consumption of hallucinogens or through other natural means (fasting, singing, drumming, etc) may have served as a sort of cultural glue that held together large social groups and families. The role hallucinogens in human evolution, however, is not as primary drivers of physical evolution but as players in the human communication framework by allowing us to consciously manipulate mental states and explore new pathways of knowledge.
The question for the future is to what extent these same forces that generated the great leap about 100,000 years ago might still be operating. Previc believes that our society is becoming increasingly dopaminergic. While the dopamine increases may have been good in the transformation of 100,000 years ago, carried to an extreme it can result in an increasingly frenetic society of individuals possessing “a sense of personal destiny, a religious/cosmic preoccupation, an obsession with achieving goals and conquests, an emotional detachment that in many cases leads to ruthlessness, and a risk-taking mentality.” (10) Previc traces the seeming increasing incidences of psychosis, autism, and other psychological disorders in industrialized societies as well as our propensity for war and environmental destruction to high levels of dopamine. While I don’t buy into any of Wright and Gynn’s theories about human evolution or their proposed solutions, they may have a point that there is a degree of imbalance in operation of the hemispheres of our brain. We may have untapped abilities that our left brain predominance prevents us from using. Alan Snyder has done research showing that savant like abilities can be induced in ordinary people by inhibiting the left temporal lobe with transcranial magnetic stimulation (11). His theory is everyone has savant-like abilities but the operation of our more analytically and language oriented left hemisphere prohibits their manifestation.
While I have argued in other posts that increasing human intelligence and creativity on a purely biological foundation might be difficult, that does not mean that it is completely impossible and that future significant advances can be made only through technology (such as Snyder’s). We know, for example, that meditation can produce enhanced connectivity in the brain. (12) Evolution may still be continuing and not all going in the direction that Previc fears. There may still be a good deal of underutilized potential in our current brain that could be manifested with perhaps small biological changes.
Might present humans be as primitive to future humans as Homo erectus was to Mozart?
4-Phonemic Diversity Supports a Serial Founder Effect Model of Language Expansion from Africa Quentin D. Atkinson Science 332, 346 (2011);
6-Normal neuroanatomical variation in the human brain: An MRI-volumetric study. John S. Allen1,2,*, Hanna Damasio1, Thomas J. Grabo. American Journal of Physical Anthropology, Volume 118, Issue 4, pages 341–358, August 2002
7-Previc F (2009). The Dopaminergic Mind in Human Evolution and History Cambridge University Press. ISBN 978-0-521-51699-0.
8 – Ramachandran , V. S. Mirror Neurons and imitation learning as the driving force behind “the great leap forward” in human evolution, 2000.
10- Previc Op Cit.
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