Yuck! More Evidence that Disgust Influences Our Moral Judgments

Disgust is an emotion that has evolved to protect us from ingesting toxins that could be potentially harmful to our survival and ultimately, to our ability to pass on our genes. Charles Darwin (1872) described disgust as “something revolting, primarily in relation to the sense of taste as actually perceived or vividly imagined” (p. 253). As demonstrated by Paul Ekman’s research, disgust is a cross-cultural human emotion. Humans in all cultures recognize the distinctive facial expression of the wrinkled nose, curled lips and protruding tongue as a reaction to disgusting stimuli.

Although the emotion of disgust has evolved to protect us from the consumption of harmful toxins, it is also intimately involved in our moral decision-making. Haidt (2000) proposed an intuitional model of moral judgments. His model suggests that our moral decisions are based on automatic, emotional reactions rather than conscious reasoning. According to his model, moral reasoning provides us with a post hoc rationalization for our moral judgments rather than the moral judgment itself.

The automatic emotions that influence our moral judgments are referred to as moral emotions. They include emotions such as anger, disgust, embarrassment, empathy etc. Rozin and Haidt (2000) extended the definition of disgust to include disgust moral offenses. In support of their new definition of disgust, Rozin and colleagues (1997) found that moral vegetarians are more disgusted by meat than health vegetarians. Recent research has also suggested that sensitivity to disgust is related to ethnocentrism (Navarrete & Fessler, 2006) as well as various politically conservative issues including abortion, immigration, homosexual marriage and stem-cell research, as well as prejudice toward homosexuals (Terrizzi & Ventis, 2006; Inbar, Pizarro, Knobe & Bloom, 2008). Disgust sensitivity has also been found to be correlated with other variables such as right-wing authoritarianism, religious fundamentalism (Terrizzi & Ventis, 2006) and religious obsessions (Olatunji, Tolin, Huppert & Lohr, 2005).

More recently Schnall and Colleagues (2008) conducted a series of four experiments in which they manipulated disgust using “fart spray”, making the lab dirty (stained and stick desk, chewed pen, pizza boxes, etc.), recalling disgusting experiences and showing disgusting video footage. The results of their first study indicated that the participants who were exposed to the “fart spray” had more severe moral reactions to first cousins marrying and having sex. In the remaining studies, the researchers found that disgust only influenced the moral judgments of those who exhibited high levels of private body consciousness.

Our moral judgments may not be as rational as we like to think that they are. Research is beginning to reveal that our behavior and decision-making is often determined by automatic, emotive processes, which have evolved to ease our decision-making in order to make it easier for us to function adaptively in our social worlds. The evidence here suggests that disgust is one of those emotions that can influence our moral decision-making. Disgust, which is an emotion that has evolved to protect us from consuming potentially harmful substances, can be co-opted by our moral decision-making processes to make decisions about moral issues.

Darwin, C. (1872). The expression of emotion in man and animals. Chicago: University of Chicago Press.

Haidt, J. (2001). The emotional dog and its rational tail: A social intuitionist approach to moral judgment. Psychological Review, 108(4), 814-834.

Inbar, Y., Pizarro, D., Knobe, J., & Bloom, P. (2008). Disgust sensitivity predicts intuitive disapproval of gays. Manuscript submitted for publication.

Navarrete, C. D., & Fessler, D. M. T. (2006). Disease avoidance and ethnocentrism: The effects of disease vulnerability and disgust sensitivity on intergroup attitudes. Evolution and Human Behavior, 27(4), 270-282.

Olatunji, B. O., Tolin, D. F.; Huppert, J. D. & Lohr, J. M. (2005). The relation between fearfulness, disgust sensitivity and religious obsessions in a non-clinical sample. Personality and Individual Differences, 38(4), 891-902.

Rozin, P., Haidt, J., McCauley, C., & Imada, S. (1997). Disgust: Preadaptation and the cultural evolution of a food-based emotion. In H. MacBeth (Ed.) Food preferences and taste. Providence: Berghahn Books, 65-82.

Rozin, P., Haidt, J., & McCauley, C. R. (2000). Disgust. In M. Lewis & J. M. Haviland-Jones (Eds.), Handbook of emotions, 2nd Edition (pp. 637-653) New York: Guilford Press.

Schnall, S., Haidt, J., Clore, G., & Jordan, A. (2008). Disgust as embodied moral judgment. Personality and Social Psychology Bulletin, 34(8), 1096-1109.

Terrizzi, J., & Ventis, L. (2007, May). Prejudicial attitudes toward homosexuals: The competing roles of moral reasoning and the moral emotion of disgust. Presented as a talk at the annual meeting for the Human Behavior and Evolution Society, Williamsburg, VA.

Top Five Reasons for Wanting a Presidential Debate on Science

The first editorial in the February 7th issue of Nature discusses a petition for a presidential debate that would focus on scientific and technological issues. There has been significant support for the idea of a presidential debate on science.

Numerous Nobel laureates, scientific organizations, government leaders, and renowned scientists have signed the petition. Some of the organizations and individuals who have joined the campaign include Science Magazine, American Association for the Advancement of Science, Skeptical Inquirer Magazine, Craig Venter, Steven Pinker, Sean Carroll, James Watson, and my personal favorite, Bill Nye the Science Guy. For a complete list go to www.sciencedebate2008.com

Here are my top five reasons for wanting a presidential debate that focuses on science.

1. I want a well informed president who understands the value of having a premier scientific community. I want a president who does not allow faith to stand in the way of scientific advancement, who understands the value of reason and skeptical inquiry. I want a president who understands the value of changing positions when the evidence supports it.

2. Whether we believe it or not, our planet is getting warmer and most scientists agree that we are at least partially to blame. I want a president that will address the problem of global warming and climate change and will listen to the recommendations of the scientific community.

3. I want a president who will support stem cell research even if the ethical issues are still not resolved.

4. I want a president who will make funds available for the development of alternative fuel sources.

5. I want a president who will not allow creationism in the class room, a president who understands the value of teaching evolution.

Please consider signing the petition for a presidential debate on science. We do not want another president who will neglect science.

Why We Kill Each Other: The Evolution of War

In order to understand why we kill each other, the concept of war must be approached from an objective perspective. It is too simplistic and uninformative to qualitatively state that all war is bad or that all war is good. The role of the scientist is not to inform us whether a war (or war in general) is morally right or wrong. It is, however, the scientist’s role to help explain why we kill each other. What function does it serve? What triggers it? Scientists and specifically anthropologists, biologists, and psychologists, who study human beings, have a great responsibility when it comes to explaining war.

Last year, Steven Pinker gave a lecture on violence. He explained that years of data suggest that the prevalence of violence is lessening. Even though that may be the case, he indicates that this finding should encourage us to be complacent. War is still a problem that could threaten the survival of our species. Pinker suggests that we approach the question of war differently. We should not be asking why we go to war. We should be asking why we are becoming more peaceful. The answer to this question may provide us with a solution to the problem of war.

My perspective is that we need to be asking both questions. We need to know why we fight. What function does it serve? On the other hand, we also need to be asking the question: “What makes us peaceful?”

In David Livingstone Smith’s book, The Most Dangerous Animal, Smith approaches the problem of war from both angles. Early theories of human nature have insinuated either that human beings were innately good or inherently evil. Like the nature vs. nurture theory that we were taught in college, this is a false dichotomy. Humans are neither good nor evil. There are times when we do dastardly things and there are times when we are altruistic. The idea of the noble savage is a myth as is the idea that primitive humans were barbarous murders (although you are far more likely to be murdered in a hunter-gatherer society than you are in an agrarian culture).

David Livingstone Smith provides vivid anthropological evidence of war in our ancestral past. He also elucidates a similar phenomenon, raiding, in our closest living relatives, the chimpanzee.

One of the reasons that people do not like to approach topics such as war from an evolutionary perspective is because they falsely assume that it moralizes issue. They believe that providing an evolutionary explanation for war somehow justifies it. This is simply not true. It is known as the naturalistic fallacy, the belief that whatever occurs in nature is good.

Additionally, people dislike the evolutionary approach to war because they think that it relieves people of responsibility. If there is a biological explanation for something, it is impossible to hold someone responsible for it. Fear of biological determinism is not a sufficient excuse for understanding the evolutionary biomechanics of war.

These people who are worried about evolutionary explanations of human behavior are also afraid that such explanations may brand behaviors as incurable. This is also simply untrue. For example, consider nearsightedness or myopia. Myopia is a biological problem, which can be cured by corrective lenses or lasik eye surgery. The only way that we can correct the problem of war is if we can understand truth about why we fight.

So why do we fight? David Livingstone Smith did an excellent job of providing evidence for our evolutionary and biological penchant for war and provided some insight into why we fight. However, you still come away from the book unsatisfied with our current understanding of war. Smith’s greatest success was getting the dialogue of an evolutionary understanding of war started. To my knowledge, his is the first book written on the topic.

There is no satisfying answer to the question of why we go to war. But there are several interesting insights. Humans are equipped with a sense of kinship. We love the people who share our genes, whether we like it or not. Our sense of kinship does not stop at genetic relatedness. We also have a sense of kinship with the groups that we affiliate with and we will do anything to protect them. Our kinship is often exploited by nations and religions, not surprisingly the two institutions that are responsible for most, if not all, wars. The short and unsatisfying answer of why we fight is because it feels good. We become enthused zealots who want to destroy the evil that threatens our groups.

What stops us from killing? Fortunately, we have evolved a mechanism that also prevents us from killing. This is something we can be optimistic about. Most humans are endowed with a sense of disgust. When we see pictures of mutilated human bodies, we are appalled. Our sense of disgust with the murder of our fellow humans is so strong that most people who have killed other human beings are haunted by the memory and suffer from post-traumatic stress disorder.

David Livingstone Smith provides an excellent survey of war from an evolutionary perspective. His book is full of all sorts of insights that help explain why we fight and why we don’t. I recommend The Most Dangerous Animal to anybody who is seriously interested in understanding the mechanics of why we go to war.

The Adaptive Value of Exaggerated Strength: The Case of Violent Human Yells

“What is a human being in a rage? On my sacred honor, nothing but a human beast! The next time it happens to you, look at yourself in the glass; and you will find your soul gone out of you at your face, and nothing left but an animal—and a bad, a villainous bad animal, too!”
Wilkie Collins
Poor Miss Finch (1908)

Animals have evolved numerous strategies and adaptations to display their strength in order to avoid predation. Certain birds will puff up their feathers to appear larger than they truly are. Gorillas will bang on their chests. The hair of dogs and cats will stand on end. In some cases these adaptations warn potential predators of real dangers. For example, poisonous frogs are brightly colored to warn predators that if they eat them, it will be their last meal.

However, in some cases animals will bluff their predators. They will exaggerate their strengths and pretend to be more deadly than they are. Some animals will evolve bright colors akin to those of poisonous animals, but they will not be poisonous themselves. Chimpanzees will fly into a rage and shake trees in order to convince others in the group that he is powerful.

Humans are no exception. We are governed by the same rules as the rest of the animal kingdom. We fly into rages. At the annual meeting for the Human Behavior and Evolution Society in Williamsburg, Virginia, Aaron Sell presented some research findings that indicate the adaptive value of human violent yells.

Sell found that: 1 strength is detectable from voices, 2 the detection of strength from voices is cross-cultural, and 3 strength is exaggerated when the voice is a violent yell. More specifically, when participants listened to a violent yell, they had a tendency to overestimate height, weight, and strength of the yeller.

The next time that you fly into a rage, take Wilkie Collins’s advice and look at yourself in the mirror. Maybe you will recognize that you too are an animal. Maybe it will change your perception of what it is to be a human.

Evolutionary Robotics, Self-Perception, and Evolutionary Theory

Evolutionary robotics is a relatively new field that integrates evolutionary theory, artificial intelligence, and robotics. Researchers in the field of evolutionary robotics create fitness functions that allow genetic algorithms or robotic controls to evolve over time. Essentially, evolutionary robotics can model processes of evolutionary learning in which a robot can understand and replicate its own form.
Recently, Hod Lipson, a professor in evolutionary robotics at the Cornell University, gave a talk at the Human Behavior and Evolution Society’s annual meeting in Williamsburg, VA. His talk was entitled “What do Robots Dream of? Emergent Self-Models in Machine Minds.” In his talk, he explained that researching robotic systems has not only practical implications (e.g. industrial robotics), but it can also elucidate the complexities of human development, evolution, and human behavior.
During his lecture, he discussed some of the many research projects that he has been working on at Cornell. Two of the projects that were of most interest to me were the robots that cold model there own structure and robots that could self-replicate.
Self-Modeling Robots
Lipson and his colleagues have found that certain fitness functions can allow robots to model and understand their own structure. Although robots do not yet have what we often refer to as consciousness, they do have the ability to recognize changes in their robotic structure through a process of continuous self-modeling. For example, a robot that has five appendages can recognize when one of its appendages is amputated and it can adapt its behavior to be congruent with its new structure.
Self-Replicating Robots
Lipson and his colleagues have also found that they can use certain fitness functions and programming to design robots that can replicate themselves. These robots not only have the ability to model themselves, but they also have the ability to construct a replication of themselves. Although they are not self-replicators to the extent that we are, they can put pre-constructed robotic parts together and essentially recreate themselves.
Evolutionary Robotics and Consciousness
So what does evolutionary robotics have to do with the human perception of consciousness? A couple of months ago, I published a post which described Douglass Hofstader’s perspective on consciousness, which suggests that we are evolved perceivers that have turned our perceptions on ourselves to create the illusion of consciousness and self-perception. Evolutionary robotics may shed a different light on self-perception. Maybe our perception of consciousness and self is nothing more than a self-model which allows us to adapt our behavior to the structure of our biological system.

For futher reading, check out these articles.

Resilient Machines Through Continuous Self-Modeling
Reproducing Robots

Why Does Disgust Induction Cause Conservatives to Become More Prejudice but Liberals Less Prejudice?

For the purposes of this post, I am going to refer to high authoritarians as conservatives and low authoritarians as liberals. I have two reasons for doing this: 1. Political conservatism is strongly correlated with right-wing authoritarianism and 2. Liberal and conservative are terms that are more manageable and easily understood.
There are many possible reasons why conservatives and liberals react differently to disgust induction. Haidt’s research suggests that liberals and conservatives differ in regard to their moral emotions. In other words, conservatives and liberals base their moral judgments on different emotions. For example, liberals are more sensitive to empathy whereas conservatives are more sensitive to disgust.
One possible reason why conservatives become more prejudice when disgusted may be because they are more sensitive to disgust. But this does not help explain why liberals become less prejudice when they are disgusted.
It is possible that liberals are averse to prejudice. The aversive racism literature suggests that people avoid expressing prejudicial attitudes so they are not seen as bigots. Thus, liberals are disgusted at the prospect of being prejudice whereas conservatives are disgusted by homosexuality.
Disgust is an emotion that originally evolved to avoid oral ingestion of contaminants as Darwin suggested in The Expression of Emotions in Man and Animals. More recently, Haidt and colleagues have indicated that morally repugnant acts can induce disgust. My hunch is that evolution designed the emotion of disgust as a general mechanism for the avoidance of undesirable stimuli but our culture is what tweaks the knobs.
More research needs to be done to confirm this hypothesis.

More Evidence for the Role of Moral Emotions in the Formation of Moral Judgments

I recently posted some of the findings from my thesis, which suggests that moral emotions are more predictive of moral judgments than moral reasoning. Specifically, people who are high in disgust sensitivity and high in moral development are just as prejudice toward homosexuals as those who are low in moral reasoning, which indicates that disgust can overwhelm our ability to reason.

In the second study of my thesis, I found that inducing disgust can make certain individuals more prejudice toward homosexuals while making other individuals report less prejudice.

Participants in this study were asked to read one of two scenarios and write a brief paragraph describing their physical and emotional reactions. Half of the participants imagined what it would be like to consume a bowl of maggots and the other half described what it would be like to eat a bowl of lettuce.

Following the experimental manipulation, the participants completed measures of prejudice toward homosexuals, disgust sensitivity, and authoritarianism. Authoritarianism was measured using the right-wing authoritarianism scale, which assess conventionalism, authoritarian submission, and aggression toward out-groups. Traditionally, individuals who score high on the right-wing authoritarianism scale are more likely to be prejudice toward homosexuals, minorities, and more likely to be politically conservative.

Disgust induction for individuals who scored high on the authoritarianism scale resulted in an increase in prejudicial attitudes toward homosexuals as compared to those in the control group. In addition, disgust induction for those who scored low on the authoritarianism scale led to a decrease in prejudicial attitudes toward homosexuals as compared to those in the control group.

These results demonstrate that conservatives and liberals are differentially affected by the moral emotion of disgust.

Mate Poaching: How Rivals Intend to Steal Your Mate

Evolutionary psychology has paid a lot of attention to mating strategies. Recent research has paid specific attention to strategies that people use to attract mates who are already in a committed relationship. Psychologists refer to these tactics as “mate poaching.”

David Schmitt, an evolutionary psychologist from Bradley University, and David Buss (2001), an evolutionary psychologist from the University of Texas at Austin, have defined mate poaching as “behavior intended to attract someone who is already in a romantic relationship.”

Schmitt and Buss’s (2001) research indicates that mate poaching is relatively common. They found that 50% of the participants in their study have attempted mate poaching and 80% reported that that they were victims of mate poaching, either receiving attraction attempts directed at themselves or observing attraction attempts on their partners.

In their article, Nifty Ways to Leave Your Lover, Schmitt and Todd Shakelford (2003), an evolutionary psychologist from the Florida Atlantic University, identifies the strategies that people use to encourage and disguise mate poaching. Their results indicated that offering sexual access and demonstrating beauty were effective strategies for females to encourage mate poaching. For men, demonstrating resources and being generous encouraged mate poaching.

Keep your eyes open for mate poachers. If you are in a romantic relationship, you may be in danger of having your mate poached. Remember, mate poaching is common. Many of us know mate poachers or have been mate poachers ourselves.

Do you know any mate poachers?

Learn more about mate poaching.

Evolution is Not Magic: In Response to Mr. or Ms. Anonymous

Dear Anonymous, thank you for your comment, but I fear that you grossly misunderstand evolution. Evolution is not a magic trick and does not occur by random chance. It is a systematic process of gradual adaptation that takes place over millions of years.
Do yourself a favor and pick up a science book! Try Richard Dawkins’s The Blind Watchmaker.
Also, you suggest that I am “to(o) afraid” to believe in God because He will hold me accountable for my actions. This is a rather presumptuous allegation. I do not need a god to bee good. I am a humanist and as Kurt Vonnegut said, “Humanism is trying to behave decently without expectation of rewards or punishment after you are dead.”
If you have any doubts that a person needs to believe in God to have a moral compass, read Marc Hauser’s Moral Minds. Hauser presents a cogent argument for the evolution of a universal moral grammar.
Maybe it is you, Mr. or Ms. Anonymous, who is afraid. Maybe you feel that you can not be good without religion as your crutch. Maybe you are afraid of death and need to believe in an afterlife for comfort. Do not project your fear upon the rest of us!

Reason vs. Faith: Move Over Religion, Science is Moving In

I am sure that everybody remembers Kirk Cameron, the child star from “Growing Pains.” Well, he grew up to be a Christian Fundamental Bible Pusher. Kirk and his friend Ray Comfort are pushing a program called "The Way of the Master," which explains why all non-christians are doomed to hell. They are so inane that they have even gone as far as to reject the existence of evolution.

There is nothing I hate more than when religion buts its nose into science. Stephen Jay Gould once said that science and religion are non-overlapping magisteria. I do not subscribe to this perspective. I side with Richard Dawkins, who suggests that faith and reason are incompatible. In fact, faith is defined as belief without reason.

And like Daniel Dennett, I believe that religion is a natural phenomenon that should be subjected to the same scientific scrutiny as all other phenomena.

It does not do any good to invoke a supernatural explanation (including God or gods) to explain a complex system. Explaining the existence of life as the work of a magician whose powers are beyond our comprehension does not enhance our understanding of how life came to evolve. Life did not appear on earth by some elaborate, inexplicable magic trick. Life evolved.

Anyway, I am done spouting off. If you want to see the Rational Response Squad destroy Kirk Cameron and Ray Comfort’s argument for the existence of God, watch Nightline tonight (May 9, 2007) on ABC or check out the nightline website.

To read more about reason vs. faith or science and religion, check out Bertrand Russell's Why I am not a Christian, Carl Sagan’s The Demon-haunted World, Richard Dawkins’s God Delusion, Daniel Dennett’s Breaking the Spell, and Sam Harriss’s The End of Faith.

Science Blogs

Some of my friends have taken it upon themselves to pimp my blog by referring to people to my site. I am writing this post to return the favor.

First of all, I would like to say that Like a Lake is the most awesomest blog in the intergalactic blogosphere. If you want to know anything about advancements in the wide world of science, especially psychology and evolution, check out this blog. The administrator of the site is a good friend of mine who is in the M.A. program at the College of William and Mary. He is a boy genius. Check his site out.

Second of all and finally, I would like everybody to visit Dr. Yeti’s blog. He is a friend from Juniata College who is now in a Ph.D. program in Pittsburgh, PA, the greatest city on earth. If you don’t learn anything on his blog, at least you will get a laugh. Not only is he science genius he is a master of dark comedy. I guess you have to be to study yeast infections or whatever he studies.

A Tribute to Kurt Vonnegut

As most of you probably already know, Kurt Vonnegut passed away April 11, 2007. Kurt Vonnegut was one of America's greatest authors. He was probably best known for his satire and black comedy. His many novels include Slaughterhouse-Five, Breakfast of Champions, Player Piano, and The Sirens of Titan.

I just finished reading Player Piano. In it, Vonnegut describes a world in which machines take over everything. Keep in mind that this book was written in the 1950's, well before self-checkouts. Vonnegut's foresight is uncanny.

Currently, I am reading The Sirens of Titan in which Vonnegut portrays the ease in which humans are seduced into believing in religion. This issue is particularly relevant to modern times. Faith and reason are incompatible and unquestioned faith in religion can lead to disastrous consequences.

If you haven't yet read any of Vonnegut's books, do yourself a favor and pick one up.

Moral Emotions vs. Moral Reasoning

Psychologist are currently debating the underlying processes involved in our moral judgments. Some psychologists believe that our moral judgments are caused by automatic unconscious moral intuitions whereas others believe they are due to conscious reasoning and reflection.

Traditionally, psychologists subscribed to the rationalist perspective. Rationalist proponents have included Jean Piaget, Lawrence Kohlberg, and James Rest. According to their perspective, moral reasoning follows a cognitive-developmental trajectory in which individuals progress from basing their moral judgments on selfish issues early in development to basing them on universal ethical principles later in development.

More recent evidence, however, suggests that moral judgments may result from quick, automatic flashes of emotion. The intuitionist perspective assumes that moral reasoning serves as a post hoc rationalization rather than a cause of moral judgments.

In support of the intuitionis perspective, Jonathan Haidt found that when participants were asked to imagine a scenario in which a brother and sister have a sexual encounter, participants invariably label the behavior as morally wrong. However, they have a difficult time explaining why they find immoral. Participants often cite the danger of inbreeding and the emotional damage that could be caused by the sexual encounter. When the researcher reminds them that the brother and sister used two forms of protection and neither of them was emotionally affected by the encounter, the participants respond by saying something like “I don’t know, I can’t explain it. I just know it is wrong.”

So if it is not moral reasoning that causes our moral judgements, what is it? Haidt suggest that it is our moral emotions. These emotions include empathy, guilt, embarassment, anger, disgust, etc.

In a recent attempt to determine whether moral reasoning or moral emotions played a bigger role in predicting moral judgments, my advisor and I examined the roles of moral reasoning and the moral emotion of disgust in predicting individuals' attitudes toward homosexuality.

We found that individuals who were high in moral reasoning were less likely to hold prejudicial attitudes toward homosexuals and that individuals who were sensitive to disgust were more likely to exhibit prejudicial attitudes toward homosexuals.

More importantly, our results showed that the moral emotion of disgust overwhelms moral reasoning such that individuals who are high in both moral reasoning and disgust ressemble those who are low in moral reasoning in regard to their prejudicial attitudes toward homosexuals.

Additionally, people who were high in disgust were more likely to be anti-abortion, more likely to want a stricter immigration policy, more likely to support the war in Iraq, and less likely to support terminal patients' right to die.

In his book, The Expression of the Emotions in Man and Animals, Darwin (1872) refers to disgust as “something revolting, primarily in relation to the sense of taste, as actually perceived or vividly imagined." Although, the emotion of disgust evolved for the purpose of avoiding oral contamination. The evidence presented here suggests that it also serves a secondary as one of our moral emotions.

Click here and learn more about the moral emotions.

The Evolution of Sickness

Just yesterday I came down with a horrible case of the flu, which is why I am writing this post. Usually when we are sick, we do not spend much time thinking about what the evolutionary functions of our symptoms are. If we do think about it, we usually think about it from our own perspective, not the perspective of the germ.
So, why do we get sick? What is the adaptive function of having the diarrhea and vomiting? Why do we get a fever? Randolph Nesse and George Williams present an evolutionary explanation to these questions in their book, Why We Get Sick: The New Science of Darwinian Medicine.
The short answer to the question of why we vomit and get the diarrhea when we have the flu is because it is adaptive for the germ. It is in the germ’s best interest to spread itself and it just so happens that causing us to vomit and diarrhea are effective methods for achieving this.
The fever, on the other hand, is not in the germ’s best interest. It is an adaptive function of the body, an attempt to kill the germ.
To learn more about Darwinian Medicine, check out this website: http://darwinianmedicine.org/
Also, read Why We Get Sick.

The Evolution of a Moral Faculty

Some religious opponents argue that we need religion because it provides us with a moral compass. According to them, without religion we would be wicked, hedonistic creatures that only looked out for their own benefit. But what if we didn’t need religion to be moral? What if evolution endowed us with the components that we need to make moral decisions?

In Marc Hauser’s newest book, Moral Minds, he suggests that evolution has given us the tools that we need to make decisions about right and wrong. He compares this faculty to the evolution of language and describes it as a universal moral grammar. Much of Hauser’s book focuses on our ability to perceive intention and the intentional system’s role in producing decisions about right and wrong.

The crux of Hauser’s argument is based on research that uses a moral dilemma about a trolley that is out of control. Participants are given one of two scenarios:

In the first scenario participants are told that a trolley is out of control and 5 people are standing on the track unable to escape. The only way to avoid the death of the five people is to pull a lever that will cause the train to switch tracks, but there is another person on that track. They are then asked whether or not someone should pull the lever sacrificing 1 person to save the other 5.

In the second scenario participants are confronted with the same out of control trolley, but this time they are told that the lever will drop a large person in front of the trolley, which will cause the trolley to stop, thus saving the five individuals.

What Hauser and his colleagues found was that individuals confronted with the first scenario will, more often than not, say that it is ok to pull the lever. However, those who are given the second scenario will, more often than not, say that it is wrong to pull the lever. Hauser believes that the reason there is a difference between the responses to these two scenarios is because the victim in scenario one would be a foreseeable casualty, but the victim in the second scenario would be an intended consequence.

This, of course, is a simplified version of Hauser’s argument. Check out his book, Moral Minds, for his complete argument for an evolved moral capacity.