Primeiro uma teoria mais excêntrica, onde o uso de drogas teria tido um papel mais importante na evolução das capacidades cognitivas humanas:
Perhaps the most famous of Terence McKenna's theories and observations is his explanation for the origin of modern human consciousness and culture. McKenna theorized that as the North African jungles receded, near the end of the most recent ice age, giving way to savannas and grasslands, a branch of our tree-dwelling primate ancestors left the forest canopy and began to live in the open areas outside of the forest. There they experimented with new varieties of foods as they adapted, physically and mentally, to their new environment.
Among the new food items found in this new environment were psilocybin-containing mushrooms growing near the dung of ungulate herds that occupied the savannas and grasslands at that time. McKenna, referencing the research of Roland L. Fisher, Ph.D. (College of Optometry and Departments of Psychiatry and Pharmacology, College of Medicine, The Ohio State University)[14] [15] [16] [17], claimed that enhancement of visual acuity was an effect of psilocybin at low doses, and supposed that this would have conferred an adaptive advantage. He also argued that the effects of slightly larger doses, including sexual arousal (not reported as a typical effect in scientific studies[citation needed]) — and in still larger doses, ecstatic hallucinations and glossolalia — gave selective evolutionary advantages to members of those tribes who partook of it. There were many changes caused by the introduction of this psychoactive mushroom to the primate diet. McKenna hypothesizes, for instance, that synesthesia (the blurring of boundaries between the senses) caused by psilocybin led to the development of spoken language: the ability to form pictures in another person's mind through the use of vocal sounds.
About 12,000 years ago, further climate changes removed psilocybin-containing mushrooms from the human diet. McKenna argued that this event resulted in a new set of profound changes in our species as we reverted to the previous brutal primate social structures that had been modified and/or repressed by frequent consumption of psilocybin.
McKenna did not attempt to defend his hypotheses through rigorous scientific evidence; he consciously self-identified as a type of shaman, or ethnobotanist. McKenna and his followers view his theories as speculation that is at a minimum scientifically feasible and arguably gifted by special knowledge due to psychedelic plants. His hypothesis that psilocybin induced a phase change in human evolution is necessarily based on a great deal of speculation that interpolates between the few fragmentary facts we know about hominid and early human development, but he argued that the ability to metabolize any dietary component could, in principle, confer a selective advantage. Many find this explanation implausible, as it suggests a Lamarckian interpretation of evolution wherein acquired secondary characteristics (e.g. an adaptave advantage resulting from consuming a hallucinogen) are assumed to be propagated genetically. However, McKenna also suggests that the cultural pattern of the mushroom-using primates is transformed through this process as well (great-horned-mushroom-goddess religion). In this light, it is arguable that culture and language would have been the medium of transference, rather than genetics. An article in New Scientist July 2008 now suggests Mckenna is closer to the mark than previously thought: "characteristics acquired during an individuals' lifetime can be passed on to their offspring. Over the past decade it has become increasingly clear that environmental factors such as diet or stress, can have biological consequences that are transmitted to offspring without a single change to the gene sequences taking place." A llace." A live recording of his "Stoned Ape" hypothesis can be found on the CD, "Conversations on the Edge of Magic" (recorded live at the Starwood Festival).
Agora outras duas com os pés mais assentados no chão. A primeira sugere que as substâncias viciantes, geralmente toxinas usadas para defesa das plantas contra os herbívoros, podem talvez funcionar como um tipo de adição ao nosso sistema imune, já que nem todos os seres são igualmente imunes a todas as toxinas.
[physorg]
From chocolate and caffeine to nicotine and cocaine, many of our most addictive foods and drugs come from plant toxins. Considering that plants originally developed these toxins to deter herbivorous predators, it’s ironic that humans and other mammals don’t merely tolerate the toxins, but can crave them and even develop dependencies on them.
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Throughout history, plants have created their toxins by mimicking their own molecules that regulate metabolism, growth and reproduction. When ingested by herbivores, some of these molecules can interfere with nearly every step in the animal’s neural signaling process.
In current evolutionary interpretations of drug addiction, these toxic substances trigger the brain’s reward center by rewiring the brain’s natural reward circuits, and falsely indicating a fitness benefit and blocking painful feelings. But, as Sullivan, Hagen, and Hammerstein show, this explanation makes several assumptions that contradict evidence from previous studies. Most significantly, it assumes that humans evolved in environments without exposure to drugs, and that the brain never evolved to protect itself from plant toxins.
However, the researchers point to several other studies which show that the detoxification enzymes developed by animals (and which originally evolved in bacteria about 3.5 billion years ago) expanded in animals about 400 million years ago – about the same time that plants were evolving their own toxins. In other words, animals and plants seemed to have coevolved competitive genes in response to each other, which contradicts the evolutionary interpretation.
As the researchers investigated further, they compiled other studies showing evidence that humans inherited these detox genes from their mammalian ancestors. Interestingly, although many modern animal species can tolerate plant toxins, different species possess different detox function levels. Even among humans from different geographic locations, these functions differ. Often, human populations with greater numbers of toxin-metabolizing genes originate from parts of the world that contain an abundance of those plants. For example, human populations in and near Turkey have a very high frequency of enzymes that can metabolize opiates, and the opiate poppy is native to the Turkish region.
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Based on evidence from previous studies, Sullivan, Hagen, and Hammerstein note that plant toxins may actually have some kind of benefit for animals. For instance, because plant toxins are more harmful to some species than to others, the less affected species might actually consume levels of toxin that are tolerable to themselves but much worse for the parasites or pathogens that feed on them in order to protect themselves. For example, earlier humans that consumed nicotine (in much smaller amounts than today) could have received the benefit of fewer parasitic infections. Of course, the benefits also come with trade-offs.
“The main implications for future research are that neurobiological theorists must consider facts emerging from plant ecology,” Sullivan said. “We are also planning field studies looking for relationships between human drug use and protection from helminth parasites.”
http://www.physorg.com/news127559887.html
http://rspb.royalsocietypublishing.org/content/275/1640/1231.abstract
Outra, a mais parcimoniosa de todas, sugere que o cheiro e o gosto do álcool de algumas frutas tenha servido de sinalizador de frutas nutritivas para os nossos ancestrais arborícolas. A dosagem natural costumava ser sempre moderada, e quando descobrimos a destilação, essa adaptação acabou mostrando um efeito colateral danoso.
The drunken monkey hypothesis: the study of fruit-eating animals could lead to an evolutionary understanding of human alcohol abuse
Natural History , Dec, 2004 by Dustin Stephens, Robert Dudley
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The hypothesis proposes that a strong attraction to the smell and taste of alcohol conferred a selective advantage on our primate ancestors by helping them locate nutritious fruit at the peak of ripeness. Millions of years later, in the Middle Ages, people learned to distill spirits, which potently concentrated the natural alcoholic content of fermented fruits and grains. The once advantageous appetite for alcohol became a danger to human health and well-being. Drawing on yeast biology, fruit ripening, biological anthropology, human genetics, and the emerging field of Darwinian medicine, the drunken monkey hypothesis could ultimately contribute to understanding--and perhaps even mitigating--the enormous damage done by alcohol.
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http://findarticles.com/p/articles/mi_m1134/is_10_113/ai_n8640726/
Tópico: Uso de drogas na evolução dos primatas e hominídeos (Lida 1989 vezes)