Posts Tagged ‘human animal’

Daniel Shapiro’s Alcoholism Blog Project

Tuesday, December 1st, 2009

On the surface, alcoholism seems like an evolutionary paradox (Gerald et al, 2002).  There is no apparent justification for the persistence of the over-consumption of alcohol as a phenotype when it appears to be detrimental to human survival and reproductive fitness (Gerald et al, 2002).  For millions in the contemporary global human population, alcohol is a devastating vice.  It’s a disease that negatively impacts the families, relationships, social lives, academic performance, professional careers, and health of people who suffer from it.  The U.S. alone has an estimated 14 million citizens who have a dependency on alcohol (Grohsman, 2009).    Alcoholism has come under the scope of science since it became accepted as a legitimate malady, but science has not yet come to a consensus on the root of the problem.  Some thinkers argue that alcohol dependency emerged as a maladaptive behavior resulting from adaptations that human ancestors made to their environments in order to survive, and others believe that the disease is the product of genetic variations.  However, the two explanations for how alcoholism came to be are not absolute opposites.  Rather, they are two sides of the same coin. They both explain how alcoholism connects to human evolution, so they both deserve a thorough analysis.

            Beginning with the argument that human ancestors set the precedent for contemporary alcoholism, the handicap theory of biologist Amotz Zahavi suggests that alcohol consumption was designed as an adaptive trait to assist our ancestors in their quest for reproductive success.  According to Zahavi (1993), animals attract mates with signals that display their genetic fitness.  Engaging in risky behaviors is one of these signals (Zahavi, 1993).  The excessive consumption of alcohol, in this context, provides a reliable signal our ancestors could have used to attract mating opportunities (Diamond, 1992).  In contrast, the capacity for individuals in contemporary society to consume alcohol in markedly large amounts is not an indicator that the individual will attract mating opportunities.  In reality, given the fact that alcohol over time deteriorates the body and mind, heavy drinkers are less likely to attract mates. Thus, this trait that modern humans have come into this world with as a result of ancestral actions is now maladaptive.

            Another theory for why alcohol consumption would emerge as an adaptive behavior in the ancestral environment and has persisted as a phenotype is that alcohol is found in high-energy foods, such as fruit, which played a significant role in the diets of ancient humans. (Dudley et al, 2004).  Graber (2008) tells us that creatures today still roam “forests in search of energy rich” foods like our predecessors did long ago.  For instance, the Malaysian pen-tailed tree shrew consumes fruit nectar that is “the equivalent of about nine alcoholic beverages a night” (Graber, 2008).  Some animals, like humans, eat fruit to obtain energy and thus increase the likelihood of survival.  For this reason, the cravings that humans developed for alcohol potentially developed as a result of eating food that was beneficial to our health, and just coincidentally contained alcohol.  The only problem with this data is that it doesn’t explain why only a select few of animals like alcohol and most animals don’t.  More studies on alcohol consumption in animals are needed.

            Most of the animals that actively seek out alcohol like human ancestors did are those who are closely related to us: primates (Graber, 2008).  Most animals, however, avoid substances containing high concentrations of alcohol as much as possible according to Graber (2008).  Rhesus monkeys, for instance, have shown that when given the opportunity to indulge in an un-limited supply of alcohol, they will not administer it excessively like other animals in captivity, such as chimps (Katner et al, 2007).  Why then do some animals and humans actively seek alcohol while others will not, especially if foods containing alcohol aid survival?  This is a question that has not been addressed by the environmental adaptation argument yet, but can be aptly answered by the argument that genetics are at the root of alcoholism.

            The enzymes that metabolize alcohol have genes that are found in all “living organisms” (Milton, 2004).  It has been hypothesized that the variations in the design and presence of these genes account for why some individuals (and animals) become alcoholics while others don’t.  One enzyme called “aldehyde dehydrogenase (ALDH2)” has gained notable attention from evolutionary biologists (Chai, 2005).  According to Chai (2005) individuals with the inactive allele of ALDH2 are less tolerant to alcohol, thus more prone to alcohol abuse, while individuals with the active allele of ALDH2 tolerate alcohol well and are thus protected against alcohol abuse.  To support this assertion, Chai (2005) showed that the active allele of the gene was overrepresented in the alcoholic proportion of his study.  In the study, 96% of alcoholics had an active ALDH2 genotype, and only 4% of alcoholics had an inactive ALDH2 genotype.  The 4% of alcoholics with an inactive gene create a weakness within this data.  However, this weakness can be remedied with the hypothesis that the majority of alcoholism is determined by genetics, and the minority of alcoholism is influenced by other factors such as psychological disorders or social pressures.  The effect size in this experiment appears large and indeed biologically relevant to alcoholism.  Although this study included only a small sample of alcoholics from a particular population, the implications it has for the argument that alcoholism has a significant genetic component are profound. 

            Taking the tolerance factor one step further is the study of Wang et al (2007), which found that fruit flies acquire “rapid tolerance” in response to alcohol sedation.  What happened to the flies virtually depicts what happens to all humans in varying degrees: after one exposure to alcohol, from that experience forward they will need a greater amount of alcohol in order to get as drunk.  This is dangerous for humans who have a genetic disposition to high tolerance, like fruit flies, because higher dosages of alcohol put users at higher risk for addiction.  Thus, through the building of tolerance, the process of addiction is augmented.

            Another genetic abnormality that has been linked to alcoholism is the A1 allele of the D2 Dopamine Receptor gene (Bergegren et al, 2006). The function that is commonly associated with this gene is the control of dopamine release in the limbic (reward) system of the brain. This gene has become associated with alcoholism because addicts are believed to have less dopamine flow than non-addicts, and this allele may hold the key to the variability of dopamine release.  One study found that the A1 allele of the dopamine receptor gene is “overrepresented” among alcoholics (Bergegren et al, 2006).  Although the effect size of this study was reported as small (Bergegren et al, 2006), DRD2’s role in alcoholism has been suspected since 1990 and documented in other studies.

            An additional study that focused on the presence of the DRD2 A1 allele in alcoholics also found that the gene was “overrepresented” in the alcoholic sample of the study (Blum et al, 1990).  Blum et al (1990) found that the A1 allele was present in 69% of the alcoholics in the study.  This indicates a relatively large, and biologically relevant, effect size.  However, there is also a weakness in this data because 31% of alcoholics in this study don’t have the A1 allele and still need to be accounted for.  Again, this inconsistency suggests that genes can’t be the sole cause of alcoholism.  For all the alcoholics who don’t have the A1 allele, or any other genes believed to be connected to alcoholism, other factors must be responsible for their malady (Blum et al, 1990).  Ultimately, more studies are needed to confirm genetic traits responsible for alcoholism and find other genes that make individuals susceptible to the addiction.

            The cause of alcoholism is not black or white, so to speak.  In other words, alcoholism does not seem to be rooted in the environmental adaptations of our ancestors nor genetics alone.  Rather, the disease seems to be the result of a mixture of factors.  Therefore, both arguments are correct to a certain degree.  There is strong evidence from our diets, observations of other animals, and our destructive tendencies that alcohol consumption emerged as an adaptive behavior in the ancestral environment long ago and has stuck around and become a maladaptive behavior in contemporary society.  There are also genetic studies that evince evidence of some individuals being more susceptible to alcoholism than others because of genetic variations.  A synthesis of the two arguments would serve a seeker of the truth better than the acceptance of one explanation over another.

            Our ancestors, for good reasons, drank alcohol and passed down this phenotype to us.  Even though their actions are negatively affecting us today, there is nothing that society can do to alter what has already happened.  What society can do, however, is focus on what it has to work with to change the way things are: genetics.  We know alcoholism has a strong genetic component, and the more we approach the disease biologically, the more we will be able to identify genes connected to it and be able to prevent people with an increased susceptibility to the disease from becoming alcoholics.  If we can find genes that are overrepresented in alcoholic populations, we can use these genes as indicators of the disease.  We can warn people of their potential to become alcoholics before they ever start drinking, and save many people from addiction to alcohol.  Alcoholism is a disease that can affect people regardless of race, religion, income, sex, etc.  Biologically understanding the disease will bring relief not just to a handful of people, but to millions of people all over the world, and the millions of children in generations to come.

 

 

 

Cited Sources

 

 

Secondary Sources:

 

Dudley, Robert, and Michael Dickinson. “The Comparative Biology of Ethanol Consumption: An Introduction to the Symposium.” 2004. Web. Oct. 2009. <http://sipddr.si.edu/dspace/bitstream/10088/6859/1/Dudley_and_Dickinson_2004.pdf>.

 

 

 

Graber, Cynthia. “Fact or Fiction?: Animals Like to Get Drunk.” Www.scientificamerican.com. Scientific American, 28 July 2008. Web. Oct. 2009. <http://www.scientificamerican.com/article.cfm?id=animals-like-to-get-drunk>.

 

 

 

Grohsman, B. “Alcoholism Statistics.” Www.treatment-center.net. 10 Sept. 2009. Web. 5 Nov. 2009. <http://www.treatment-centers.net/alcoholism-statistics.html>

 

 

Milton, Katharine. “Ferment in the Family Tree: Does a Frugivorous Dietary Heritage Influence Contemporary Patterns of Human Ethanol Use?” 2004. Web. 21 Oct. 2009. <http://www.cnr.berkeley.edu/miltonlab/pdfs/fermentfamily.pdf>.

 

 

Zahavi, Amotz. “The Fallacy of Conventional Signaling.” The Royal Society, 1993. Web. Oct. 2009. <http://www.jstor.org/pss/55797>.

 

Diamond, J.  1992.  The Third Chimpanzee: The Evolution and Future of the Human Animals.  HarperCollins.  New York, NY.

 

Primary Sources:

Chai, Young-Gyu, Dong-Yul Oh, Eun Kee Chung, Gil Sook Kim, Leen Kim, Yu-Sang Lee, and Ihn-Geun Choi. “Alcohol and Aldehyde Dehydrogenase Polymorphisms in Men With Type I and Type II Alcoholism.” Www.ajp.psychiatryonline.org. American Psychiatric Association, May 2005. Web. Oct. & nov. 2009. <http://ajp.psychiatryonline.org/cgi/content/full/162/5/1003>.

 

Blum, Kenneth, Ernest Noble, Sheridan Peter, Montgomery Anne, Terry Ritchie, Pudur Jagadeeswaran, Harod Nogami, Arthur Briggs, and Jay Cohn. “Allelic Association of Human Dopamine D2 Receptor Gene in Alcoholism.” Www.jama.ama-assn.org. The Journal of American Medical Association, 18 Apr. 1990. Web. 5 Nov. 2009. <http://jama.ama-assn.org/cgi/reprint/263/15/2055?ijkey=b3857c11c6da841e98214d1ab6de1ffd054e6259>.

 

Berggren, Ulf, Claudia Fahlke, Erik Aronsson, Aikaterini Karanti, Matts Eriksson, Kaj Blennow, Dag Thelle, Henrik Zetterberg, and Jan Balldin. “The TAQ1 DRD2 A1 Allele Is Associated With Alcohol-Dependence Although Its Effect Size Is Small.” Www.alcalc.oxfordjournals.org. Oxford University Press on behalf of the Medical Council on Alcohol, 2 June 2006. Web. Oct. & nov. 2009. <http://alcalc.oxfordjournals.org/cgi/content/full/41/5/479?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=%28DRD2+AND+allele+AND+1+AND+alcoholism%29&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT>.

 

Wang, Yan, Harish R. Krishnan, Alfredo Ghezzi, Jerry CP Yin, and Nigel S. Atkinson. “Drug-Induced Epigenetic Changes Produce Drug Tolerance.” Www.plosbiology.org. PLOS Biology, 16 Oct. 2007. Web. Oct. & nov. 2009. <http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.0050265>.

 

Katner, Simon N., Stefani N. Von Huben, Sophia A. Davis, Christopher C. Lay, Rebecca D. Crean, Amanda J. Roberts, Howard S. Fox, and Michael A. Taffe. “Robust and Stable Drinking Behavior Following Long-Term Oral Alcohol Intake In Rhesus Macaques.” Www.ncbi.nlm.nih.gov. NIH Public Access, 12 July 2007. Web. 9 Nov. 2009. <http://www.ncbi.nlm.nih.gov:80/pmc/articles/PMC2231844/>.

 

Gerald, M. S., and J. D. Higley. 2002. Evolutionary underpinnings of excessive alcohol

consumption. Addiction 97:415-425.


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Shapiro’s FSEM Polygamy Essay

Monday, November 2nd, 2009

Humans have lived in forager societies, which were nearly 100% polygamous (Crippen pers. comm.), for most of history.  Incidentally, in the rise of modern nation states many societies have banned bigamy in favor of monogamy.  Monogamy is the cultural norm, but this was imposed artificially.  Humans have always been, and still are polygamous.  The existence of sexual dimorphism, the theory of natural selection, and concept of parental investment support this assertion.

            Sexual dimorphism is the first signal that polygamy is a natural human behavior.  Many species in the animal kingdom are sexually dimorphic and also polygamous, indicating a causal relationship.  Theoretically, the more dimorphic a species is, the more polygamous it is.  There are slight differences between human males and females, such as: body size, formation of face, and sexual reproductive organs.  These slight differences suggest that humans are also slightly polygamous (Diamond, 1992).  By slightly polygamous, we can be specifically say that males or females rarely ever acquire more than two to three mating partners.  Although, there have been rumors of some elite individuals in history who have maintained harems consisting of more than three partners.

            Sexual preferences form in the process of sexual selection because they contribute to reproductive success (Rhodes, 2006).  Polygamy, especially for males, is logical within this context, and also consistent with Darwin’s theory of natural selection.  In human societies, the richest and most powerful males often acquire multiple wives (Diamond, 1992). The reason for this is that the more partners that males acquire, the more copies of their genes they can get into the next generation.  The former motivation, as well as the fact that males don’t have to invest as much parentally as females, drives men to acquire as many mating partners as possible.

            With the exception of the rare polyandrous societies where females acquire multiple husbands (Crippen pers. comm.), females are more selective about whom they mate with and also don’t acquire as many mates as males do.  One reason is because females have higher parental investment, and therefore need sufficient access to resources in order to raise offspring.  Another reason is because females need to select mates with the good genes so the chances that their offspring will survive are enhanced.  However, there is evidence that females are of a polygamous nature too.  Havlicek et al (2005) makes the hypothesis that females have evolved a sense based on body odor, to distinguish genetically superior males from docile males.  With this knowledge, females subconsciously seek out dominant males to mate with, even while in long term relationships with docile males, who are in this case being manipulated and used for their tendency to have higher parental investment than dominant males (Havlicek et al, 2005).  This mating strategy is not commonly found in contemporary societies, but may have played a major role in the ancestral environment given its obvious reproductive advantages.

            Monogamy is obviously not natural for humans.  More than anything, monogamy has been a practical way for governments to institute equality.  Ironically, it has created more problems than it has solved for the domestic lives of citizens.  Human ancestors set the polygamous precedent, and even though society has told us to stop, humans have not let go of their polygamous ways.  The default sexual preference of humans is still polygamy.

 

Cited Sources

 

Rhodes, G.  2006.  The evolutionary psychology of facial beauty.  Ann Rev Psych.  57: 199-226.

 

Diamond, Jared. The Third Chimpanzee: The Evolution and Future of the Human Animal. New York, New York: HarperCollins, 1992. Print.

 

Havlicek, J., Roberts, S.C., and Fleg, J.  2005.  Women’s preference for dominant male odour: effects of menstrual cycle and relationship status.  Biol. Letters.  1: 256-259.

Shapiro’s Second FSEM Essay

Thursday, October 8th, 2009

             Humans are not the only species who express themselves artistically, make and use tools, and exhibit maladaptive behaviors.  There are other species of animals that do the same activities as us. Ultimately, the reasons why we do what we do and why other species do the same are closely related. The only difference is the extent to which we pursue these activities, which is unrivaled by any other animal on Earth.

             Humans are not the only species who create art.  Chimpanzees and elephants, for example, also make art.  The difference between our art and theirs is that they only make theirs in captivity. Like us, art brings animals in captivity pleasure, “relieves boredom, and channels neurotic energy” (Diamond 1992). One compelling argument for why animals, for example, chimps, don’t create art in the wild is because they “still have their day filled with problems of finding food, surviving, and fending off rival chimp groups.”(Diamond 1992).  This points to the obvious reason why humans naturally express themselves artistically: art gives us something to do with our free time.  Of course there are other reasons why humans make art, such as status, or to trade for resources. Sheer aesthetic pleasure seems to be another factor in artistic creation for humans and other animals.  Some artists don’t sell their work.  For instance, “Franz Kafka not only didn’t publish his three great novels but even forbade his executor to do so” (Diamond 1992).  Chimps seem to have the same inclination; Diamond (1992) says they “didn’t even keep their paintings to enjoy but just discarded them”.  The process of artistic creation for some animals is satisfying in itself.

            Another aspect of existence humans share with chimps and other animals is bad habits.  Humans indulge in smoking, drinking, sky diving, and the like, but we are not alone in our risky behaviors.  An Israeli biologist named Amotz Zahavi formulated a general theory that explains bad behaviors as a biological function of evolution.  Zahavi says that all animals make signals to communicate that the “animal is being honest in its claim of superiority, precisely because those traits themselves impose handicaps” (Diamond 1992).  For example, birds of paradise grow tails up to “three feet long” (Diamond 1992).  The main difference is that the costs of bad behaviors for humans now outweigh the benefits, while the opposite is true for animals.

            Tool making and use has been one key to the evolutionary success of humans, but again we are not alone.  Our hominid relatives also make tools.  For instance, tool use is “regularly observed in chimpanzees and orangutans” (Breuer et al 2005).  Chimps often use sticks to fish for termites.  Another primate, the Aye-aye of Madagascar, uses the claw of its middle finger like a tool to extract grubs from trees for food.  Humans have devoted more energy into the development and use of tools than other animals, but tool use is clearly not unique to our species.  

            Humans are easily distracted from the rest of the animal world by our own development.  However we should not forget that we share common traits with all animals.  In fact, we share most of our DNA with chimpanzees.  When we study the characteristics of other animals – their habits, their tools, their art, – we begin to understand why we have these same characteristics ourselves.    

 

 

Works Cited

Diamond, Jared. “Animal Origins of Art.” The Third Chimpanzee. New York, New York: HarperCollins, 1992. 168-79. Print.

 

Diamond, Jared. “Why Do We Smoke, Drink, and Use Dangerous Drugs?” The Third Chimpanzee. New York, New York: HarperCollins, 1992. 192-204. Print.

 

Breuer, Thomas, Mireille Ndoundou-Hockemba, and Vicki Fishlock. “First Observation of Tool Use in Wild Gorillas.” Www.plosbiology.org. PLoS Biology, Nov. 2005. Web. Sept.-Oct. 2009. <www.plosbiology.org>.