You are currently browsing the category archive for the ‘Uncategorized’ category.

Should the ruler thirst around the humane refund?

For those who were hoping for an extensive blog on Kony 2012, I have decided to refrain. It is obvious that the primary force behind the campaign, Jason Russell, is having some serious personal issues, and so I will leave it alone for now.

Bullying blog link.

In a new book featured in the article “Humans Naturally Cooperative, Altruistic, Social”, Robert Sussman, Ph.D. and C. Robert Cloninger, MD claim that humans and other primates are inherently altruistic and that cooperation serves its own purposes, unrelated to competition. Their claim, while intriguing and attractive to most peace loving people, should incite great discussion and debate, and needs to be scrutinized carefully. Scrutiny is not something reserved for claims that we don’t agree with, but rather, needs to be the standard for all scientific claims.

In this case, the authors are making a claim that flies in the face of much of what we understand about human and non-human primate behavior and evolutionary theory. Altruism is a difficult concept to quantify in human populations, let alone non-human animals. I will mention altruism below, but first, I will focus on cooperation.

Cooperation is an important behavior in many social species, however, it is not as common as many believe. In the world of behavioral studies cooperation requires that two or more individuals act together to accomplish a task or goal, the result of which is that both gain more than they would have by acting alone. Female lions appear to cooperate when hunting, because they work together to bring down prey and are more successful hunting in prides than alone. Similarly, male chimpanzees cooperate to defend territories through group boundary patrols, the result of which is males being more successful than if they were to patrol alone [a behavior that could get them killed].

In the case of humans, cooperation is commonplace. On that point the authors and I agree on what the data indicate. We see cooperation in everything from communal farming and child-rearing, to modern day warfare, to baseball and other competitive sports. Humans are excellent cooperators, especially when compared to other animals. Through language, loyalty and a reliance on each other, we have become supreme cooperators.

The point where the authors and I diverge is in the conclusions we draw from the data. According to Sussman and Cloninger cooperation exists for its own sake, and is natural for humans and other primates. They claim that cooperation is not a by-product of competition, but rather that animals cooperate for cooperation’s sake. This largely ignores a wealth of data showing that cooperation is a strategy adopted by animals, including humans, that allows the cooperators to more effectively exploit their respective ecological niches and survive and reproduce at higher rates, than would otherwise be possible. In other words, cooperation allows individuals to more successfully compete for resources.

One of the difficulties in testing this idea in humans is that humans everywhere cooperate, a lot, and it’s hard to run an experiment where the subjects don’t cooperate. This supports the first position of Sussman and Cloninger, humans appear to “naturally” cooperate. This is nothing new, or surprising.

We have seen humans cooperating over the course of history, so many times that it doesn’t even make sense to cite individual cases. We have also seen that in those cases both parties, invariably, benefit from their cooperative actions. If both parties benefit, the behavior is seen as mutualistic and there is no need to invoke any special level of selection for the behavior. However, if those behaviors are one-sided in nature, resulting in the recipient receiving a benefit, while the provider suffers a cost, they are altruistic and need further explanation.

Almost fifty years ago Hamilton provided one possible explanation for seemingly altruistic behaviors, by pointing out that if genetic relatives live together in social groups, they should act preferentially toward one another. Kin selection has been supported in populations ranging from sickle-back fish, to ground squirrels to humans [think of the Bush and Kennedy political dynasties in the US] and has been recognized as an important factor in evolution.

Nearly forty years ago, Robert Trivers gave us one explanation for what appear to be one-sided cooperative behaviors, or altruism, reported for people worldwide. He introduced the term reciprocal altruism, which applies to both humans and non-humans, and states that if animals [including humans] have long-term social interactions that allow them to receive reciprocation of a cooperative or altruistic behavior consistently enough, they should be willing to cooperate, even if an immediate payoff is not obvious. His hypothesis has been supported over and over in numerous animal and human studies [think of political contributions by big oil].

While these two hypotheses explain much of the altruistic behaviors we see in the natural world, they do not explain them all. We still don’t know everything about altruism or altruistic behaviors, including the biochemical and psychological benefits received by the individuals providing the seemingly altruistic behaviors. One clue may be the fact that hardly anyone, anywhere feels bad when they do something for someone else. Instead, people everywhere appear to get a chemical rush out of acting cooperative and altruistic – it makes them happy. This may give an indication of the importance of those behaviors in our evolutionary past. It may be that it was so important for our ancestors to cooperate, even when their chances of immediate payoff were low, that selection favored those individuals who acted cooperatively, and they were inspired to do so because it felt good. This is somewhat like the reason that sex feels good. The short answer is: because in the evolutionary past, those who had more sex had more offspring, and those who got an immediate payoff through feeling good had more sex.

While intriguing, Sussman and Cloninger’s new book is really one of philosophy, not scientific inquiry. Their philosophy appears to be that resources are not limited, and that all organisms everywhere, do not have to compete for those resources. Much like the current rhetoric coming from one side of the debates over the economic crisis, they seem to think that resources are unlimited and that there need not be competition for those resources. This is the position one is led to if they carry out the two separate logics of: “I want everyone in America to be rich.” (Mitt Romney, 2011) and “Cooperation isn’t just a byproduct of competition, or something done only because both parties receive some benefit from the partnership, rather, altruism and cooperation are inherent in primates, including humans.” (Sussman, 2011).

Neither position is tenable if the once agreed upon fact of limited resources is recognized. For his part, Romney was pandering to the pressures exerted by the public and media over a position of not taxing corporations and wealthy individuals to shore up our economic woes. Sussman’s position, on the other hand stems from what appears to be a philosophical divide. Competition is one of the central tenets of evolutionary theory. Resources are limited for every population of animals throughout the world, resulting in competition for those resources. It is through competition that individuals are selected upon by natural forces and potential mates for their differing characteristics or traits.

It follows that it is only because they have to compete for resources that animals, including humans, cooperate and act altruistically.

I think a far more interesting question at this point, is when and why did cooperation become so intrinsically embedded in what we do as a species?

Just about 170 miles from the very spot where I’m writing this blog entry is the “Creation Museum” in Petersburg, Kentucky. It’s the most elaborate pseudoscientific construction ever created, in an attempt to convince large groups of people that a particular view, one that includes creationism and intelligent design, is correct. The “museum” goes as far as presenting dioramas of humans and dinosaurs coexisting, sometimes in a Flintstonian manner.

On the surface it is a comedy, a farce of serious museums, and if it weren’t so obvious what the founders of this “museum” were trying to accomplish, I would laugh with everyone else. However, a brief glance at their website reveals their true target demographic, and their intentions. The directors of the “Creation Museum” are targeting children with their propaganda, their online content and the programs they sponsor. They are trying to alter the basic understanding of evolution in this country, furthering their own agendas at the cost of our children’s education, and understanding of the world.

Ever since Darwin discovered natural selection, evolutionary scientists have struggled against dogmatic zealots who have pushed their agendas and personal philosophies in efforts to bend science to their own ends. From Darwin’s main critic, Bishop Wilberforce, to the “Father of Intelligent Design” Phillip Johnson, J.D., philosophical and religious agendas have threatened the science of evolution from its inception.

In recent years, groups such as the National Center for Science Education have provided rock solid arguments invalidating ideas such as intelligent design and “creation science” as scientific approaches to the world. In fact, a brief examination of their platforms reveals that they are philosophical at best, and usually theological at their core. This is not a bad thing, however, it is not science. For ideas to be scientific in nature they must produce testable hypotheses. Seemingly eloquent, but in reality ignorant, presentations of the complexity of the human eye concluding that there must be an “intelligent designer” behind such intricate forms are not scientific.

Despite the fact that it is clearly obvious that ID and “creation science” are not scientific in nature, there is still active debate among members of the general public. This is reflected in a recent Gallup Poll, which showed that while a majority of respondents believe in evolution, they are unsure about how it proceeds, or the role, if any of “God”.

I was thinking about this issue the other day when I received an email from a student in my Human Evolution class, telling me that he couldn’t make it to class that day because he had to go get an infected wisdom tooth pulled. Now, I’ve heard a lot of excuses for missing class, but this was a first, and knowing the student, I knew he must be in a fair amount of pain. I sent him a quick reply wishing him a speedy recovery and telling him that I’d see him when he returned to class. While I was replying to him, though, and throughout the rest of the day, I couldn’t help but think about the third molars in modern humans and how most people in western and non-western cultures either have them extracted or deal with impacted teeth and infections SILVESTRI ET AL ’03.

While some have argued that our jaws actually have plenty of room for our third molars, or “wisdom teeth”, empirical data do not support this position. Further, when we look at examples of earlier specimens of Homo sapiens we see that they had plenty of space for their third molars, or “wisdom teeth” TRINKAUS ET AL ’03.

These findings result in several observations and hypotheses and conclusions. First, third molars are useful in processing tough, gritty, grainy foods. Second, early humans had more space in their jaws than do modern-day humans . Third, human females prefer males with smaller, more feminine faces as long-term partners . Fourth, modern human populations eat softer, more processed food than earlier populations of humans did. These hypotheses can be tested, some have already, and the vast majority of studies support them.

Interestingly, the ID argument against hypotheses about reduction in third molars, often invoke evolutionary explanations, just without a connection to apes. In his article “Are wisdom teeth (third molars) vestiges of human evolution?” Jerry Bergman begins with this frame,

“A major conclusion of evolution is that the human jaw has shrunk from its much larger ape size to the smaller modern human size as humans evolved.”

In that initial wording in the Introduction to his article, Mr. Bergman reveals his bias and his primary issue. This is more obvious in his conclusion, when, after not providing any objective data he states that,

“The most important factor is probably diet, but the influence of other factors including mutations, needs to be examined more fully to understand why wisdom teeth are more often a problem today. The once common belief that wisdom teeth problems are related to putative evolutionary modifications has now been discredited…”. (emphasis added)

Diet (i.e. food) is one of the most important selective forces in all of evolution. Animal traits evolve in direct response to the foods they eat. Further, mutation is the source of all new variation in evolution and critical for evolution to occur. Both of the explanations used by Mr. Bergman are evolutionary in nature. It seems that the only way the Mr. Bergman can discredit ideas of humans evolving from apes is for humans to have evolved in a different way. Just a quick note to Mr. Bergman: We are apes, get over it.

The evidence all suggests that modern humans have undergone simultaneous sexual selection for smaller faces, and a relaxing of natural selection on the processing capabilities of our dentition, resulting in the current condition we observe across human populations. Adults who regularly need to have their third molars removed surgically, to prevent impaction, infection and extreme dental crowding. All of this has led me to ask the question, “How Intelligent Can a Designer be That Gave Humans “Wisdom Teeth?”

On the surface, it would seem that LeBron James and lasting peace in the Middle East have nothing in common, and I could make that argument myself, but I won’t. Instead, I will show how both are not only linked to one another, but to the celebration over the death of Osama bin Laden.

Since my original posting of Part I of this blog entry, there have been more developments surrounding this event. There have been questions about how bin Laden died, how his body was disposed of, and if he’s even dead. Beyond that, there have been questions of how bin Laden could have remained “hidden” in a million-dollar estate so close to the Pakistani military, how the US was able to get to him and just what the celebrations of his death mean for US and global society. At the same time, the “Arab Spring” in the Middle East is struggling to move forward, with draconian crackdowns in Syria, Bahrain and other countries, while the G8 pledges to support the movement. Israel and Palestine seem to be moving further from a plausible place of negotiation after Netanyahu’s obstinance during his Washington visit last week. All the while, LeBron James and his new team, the Miami Heat, steam-rolled the competition in the Eastern Conference playoffs to reach the NBA Finals for the second time in James’s storied career, where they will face the Dallas Mavericks. A fact that has many in Ohio, especially Cleveland Cavaliers owner Dan Gilbert.

So, what does the reaction to the Heat reaching the Finals have to do with the celebrations over the death of bin Laden, and peace in the Middle East? Maybe everything. As I’ve stated numerous times before, our species is a lethally, territorial, xenophobic one. Males from different communities compete over territories, and they will attack each other, lethally if possible, when they have distinct advantages or the costs of not attacking are too high. While it’s obvious what lethal, territorial xenophobia has to do with the death of bin Laden and peace in the Middle East, it might seem less clearly connected to attitudes about LeBron James and the possibility of his winning his first NBA title.

In the eyes of many in and around sports, the city of Cleveland and the state of Ohio, King James committed to the ultimate act of betrayal. He left his home state, where he was the undisputed leader of a contending franchise, and joined a new team. From the perspective of a xenophobic species, he ceased to be a member of a specific “in-group” and became one of the “others”. When LeBron left Cleveland for Miami his actions elicited very primal reactions from those that admired and adored him. For an example, look at the open letter issued by his former boss, Dan Gilbert. Those reactions and feelings haven’t any dissipated over time. Many people in the city of Cleveland, and Cavaliers fans everywhere, genuinely hate LeBron James, and they do so because they feel betrayed and abandoned. What makes it worse is that those fans feel betrayed and abandoned by “one of their own”. To further the insult, he wasn’t a role player who came off the bench, he was the “chosen one”. LeBron James was supposed to not only save the city of Cleveland from decades of disappointment, he was supposed to rule the NBA, and he was going to take the Cavaliers with him. From the perspective of a xenophobic species, the alpha male left his group to side with an enemy, resulting in his former group mates feeling betrayed and abandoned.

Those same feelings are experienced by humans in all cultures, in all contexts, regardless of where they live. When we identify someone as a member of our in-group we empathize with them in a particular, unique way. Conversely, when we identify someone as a member of an out-group, an enemy, we empathize with them little, or not at all. The reaction of Cavaliers fans to LeBron James now that he is a member of an out-group is, at its core, the same base reaction of Israelis to Palestinians, or those celebrators and revelers to the death of Osama bin Laden. To be clear, I am not claiming that the reactions of sports fans are equal to those of members of different cultures in conflict, or people fearing for their lives. I’m suggesting that the behaviors stem from the same adaptations to selective forces that favored individuals who empathized strongly with in-group members and not with members of an out-group. While the stakes are obviously much higher in the cases of the Israeli-Palestinian conflict and the on-going war with al qaeda, the feelings share the same roots. Sports are simply ritualized forms of combat and competition that allow us to act out deeply ingrained coalitional, competitive and complex behaviors in ways that are, usually, not lethal. Part of the attraction of sport is that it allows us to form in-groups and out-groups in safe, stimulating environments, where we can act out aggression, friendship, and competition. In the cases of anger towards James, celebrations over the death of bin Laden, or the situation in the Middle East, we see all three of those behaviors, and many others, acted out in very different contexts. While those differences are important for the impacts they make on individuals and on society (the departure of James from Cleveland is, obviously, nowhere near as important as a struggle for national and personal survival) it is the similarities in the reactions of the groups that reveal our evolutionary heritage. It is in the similarities in the reactions of these disparate groups that we see how rooted in our evolutionary past our current behaviors are.

At 11:35 EST on May 1, 2011 the United States and the world were provided with information that thousands have been waiting for for nearly a decade: Osama bin Laden is dead. President Barack Obama in a televised news conference informed the world that a US special forces team had raided a compound in Pakistan and killed the Al Qaeda leader. Almost immediately people started to gather outside the White House in Washington, DC and what started with 30-40 revelers turned into a world-wide event that stretched to Times Square and a Mets/Phillies game in NYC and even took hold in Athens, Ohio.

Many in the media have embraced the impromptu celebrations, and even Rush Limbaugh praised the actions of the Obama Administration (though he has since backtracked). Still, some have questioned their appropriateness, and what it says about our civilization. Recently, on the Huffington Post, Dr. Pamela Gerloff wrote about the psychology of revenge and why we shouldn’t celebrate the death of Osama bin Laden. That sentiment has spread around the social networking site Facebook in the form of a false Martin Luther King, Jr. quote,

“I mourn the loss of thousands of precious lives, but I will not rejoice in the death of one, not even an enemy. Returning hate for hate multiplies hate, adding deeper darkness to a night already devoid of stars. Darkness cannot drive out darkness: only light can do that. Hate cannot drive out hate: only love can do that.”

While it appears that the heroic, transformational civil rights leader never said these exact words, the comments are not unreasonably assigned to him, and the sentiment is the key.

A genuine, visceral backlash in response to the peaceful, patriotic mobs seen on the streets of the US and around the world is emerging in text messages, emails, tweets, and op-eds. I use the term mob here, because that is what the groups of revelers are, they are mobs. However, much like flash mobs, these are non-violent celebrations, which provide safe places to express emotions about an identified enemy and our nation. While some are morally outraged that people are celebrating the death of another human, some are skeptical of the patriotic feelings of those involved, and are uncomfortable with the public display.

In her article, Dr. Gerloff stated that, “”Celebrating” the killing of any member of our species — for example, by chanting “USA! USA!” and singing “The Star Spangled Banner” outside the White House or jubilantly demonstrating in the streets — is a violation of human dignity. Regardless of the perceived degree of “good” or “evil” in any of us, we are all, each of us, human. To celebrate the killing of a life, any life, is a failure to honor life’s inherent sanctity.” Instead, she suggested that the death of Osama bin Laden provides us with an opportunity to assess what kind of nation and species we want to be. She went on to say that, “We could start by not celebrating the killing of another.” To her credit, Dr. Gerloff stated that, “We are not a peaceful species. Nor are we a peaceful nation. The celebrations of this killing throughout the country draw attention to these facts.” However, I would argue that she and the other critics and detractors are missing an important lesson that this historic moment offers to teach us.

The reaction of thousands around the US and the world provides us with a glimpse into our own psychology. Not the psychology that has developed over the course of our lifetimes, but the psychology that has evolved over million of years of partially closed social groups of related males competing violently with other groups for resources and territories. The impromptu celebrations that began around midnight Monday morning and lasted well into the early morning hours were not planned, they were not organized, they were the rawest of human emotion and data. Those gatherings were the result of the human mind and collective experience being exposed to a life-threatening traumatic event (9/11), then provided with one, centralized cause and target of that event. The final piece of the puzzle was provided with President Obama’s address of the nation late Sunday night. Osama bin Laden, for many, represented evil, but beyond that, he represented the source of an invasion on our way of life. He was the ultimate “outsider” and the target of deep lethally xenophobic feelings that were both justified and accentuated by our government, the media and bin Laden himself.

As the leader of Al Qaeda, Osama bin Laden took it upon himself to antagonize, demonize and threaten the United States. While he may have thought that it was necessary for his own survival, when he claimed responsibility for the deaths of over 3000 Americans, the die was cast. The reaction of ordinary citizens to the news that he was dead was predictable, almost unavoidable from the perspective of evolutionary psychology. It was the reaction of a group of primates, celebrating in the elimination of a threat and rival. In those hours after the announcement, it was nothing more, nothing less, and we need to understand that. We need to understand that for all of our language and culture and “civilization” we are, at our core as a species, a lethally xenophobic primate.

In her article, Gerloff suggests that, “We will only have peace when we stop the cycle of jubilation over acts of violence. Who will stop the cycle? If not us, who? If not you and I, who will it be?” This is an admirable intellectual position to take, and one that I agree with in principle. However, it is naïve to think that we as a group can simply put aside our evolved behaviors and emotions and embrace a new psychology to “consciously evolve” toward the kind of species we aspire to be. Instead, we need to understand why the death of a leader from another community matters, and why we have such strong emotional reactions to it.

Human babies are regularly born facing the opposite direction of their mothers, a position that has often been reported to be unique to our species (Rosenberg & Trevathan, 2002). In a recent report in the journal Biology Letters, Satoshi Hirata, Koki Fuwa, Keiko Sugama, Kiyo Kusunoki and Hideko Takeshita of the Great Ape Research Institute of Hayashibara Biochemical Laboratories in Okayama, Japan report that chimpanzees also give birth to offspring in a similar position, a position called “occiput anterior”. Joseph Milton of Nature magazine reported that, “The discovery…calls into question the argument that backwards-facing babies were an important factor in the evolution of midwifery in humans.”

It has long been suggested that the regular practice of human females receiving assistance during childbirth is unique in our species and due to the typical position of human infants during the process (Rosenberg & Trevathan, 2002). Mechanically, human infants need to rotate during labor and emerge with their faces opposite those of their mothers to most effectively protect their brains. However, it has been assumed that this position makes it difficult for mothers to give birth on their own, because they can’t reach back and clear an airway for their new infants (Rosenberg & Trevathan, 2002). The result, some have argued, has been a long history of midwifery, or helpers, throughout the course of human evolution.

Hirata et al’s report has started a debate about the presumed uniqueness of human birth and what it means if chimpanzees have similar births. Interestingly, their report, which is causing so much uproar, is of three births in captivity. To further complicate matters, the researchers report to having been in the enclosures with the chimpanzees when they gave birth. While it is almost certain that their presence did not impact the orientation of the infants during labor, it is still highly irregular and not objective science. The sample size in this report, however, is a different story. Sample sizes are critical to help ensure that observations are not of anomalous phenomena. While I doubt that these three chimpanzees all had infants in irregular positions, more data is needed before conclusions can be drawn about species typical patterns during child birth in chimpanzees. Beyond this new information on childbirth in chimpanzees, more data is needed on childbirth in the other ape species. Given the long history of apes in captivity in zoos and sanctuaries, it’s surprising that those data are not already known.

If the data from this current study hold up over time, just what does it mean for studies of human evolution? Trevathan originally hypothesized that the orientation of human infants during delivery is part of the unique adaptive suite of encephalization and pelvic shape in humans, and that it was directly connected to the notion of helpers during labor (something also proposed to be unique to humans). Some researchers have taken that notion of helpers to develop hypotheses about midwifery and its history in the human lineage. While statements like the “…evolution of midwifery” are a little fanciful, most researchers agreed that the orientation of human infants during delivery, combined with the orientation of the pelvis and the difficulty of modern childbirth make it difficult for human females to deliver on their own. While it’s true that most female primates give birth on their own, there have been reports of helpers assisting during childbirth in common marmosets (Rutherford, personal communication).

One thing that was unknown before this report, and is still not completely resolved, is when the occiput anterior orientation of human infants first emerged. If these data are confirmed by further studies it could mean that this position, once thought to be unique to humans has a deep evolutionary history, or that it represents variation across primates. Simply put, we need more data to be able to say whether or not this pattern is unique to chimpanzees and humans, unique to humans, chimpanzees and bonobos, or a more generalized pattern seen in other primates. For studies of human evolution, it doesn’t shatter any paradigms, but it should serve as a lesson: We need to be as complete as possible in our data collection, as thorough as possible in our analyses, and as careful as possible in our conclusions.

As we gather more and more data, on more and more different primate and animal species, we continue to see that humans are not unique after all. Instead, the pattern that is emerging is that humans share so much in common with the other primates that the line between the two is a blur. The one thing that is clear is our place in nature. We are apes, primates, mammals, vertebrates, and the product of evolution by natural selection.

“Do chimpanzees in the wild want to kill others? Is murder common among wild chimpanzees? Do male chimps (and their cousin male humans) have “killer” “demonic” instincts towards their fellows? If you look at the data, the answer to these questions is a resounding NO! But these beliefs are “gospel” in much of popular science. This misinformation colors our view of humans and human nature. What are the ramifications?”

This was the opening paragraph of a recent blog by Dr. Darcia Narvaez on the Psychology Today website. Dr. Narvaez, an Associate Professor of Psychology at Notre Dame University, decided to tackle the question of whether or not male humans and chimpanzees are “genetically violent” – a poor choice of terminology, but I know what she’s driving at, and I’ve got a fair amount of experience in this area. So, I decided that I would take a few minutes and write up a response to Dr. Narvaez’s assertions to see if we can’t set the record straight in this regard.

The best place to start is with her opening paragraph, and we’ll look at each question and the wording she uses to see if her conclusions hold up:

“Do chimpanzees in the wild want to kill others?” I call this the Dr. Doolittle question. This question is asking what the desires and intentions are of an animal that doesn’t possess the power to communicate in a spoken language [at least not one humans understand at this point]. Therefore, the question, at its essence cannot be answered. However a few clearer, related questions can be answered:

1) Do chimpanzees in the wild avoid attacking others?
2) When chimpanzees in the wild attack others do they exhibit behaviors associated with excitement?
3) When chimpanzees in the wild attack others do they kill them when possible, or attempt to do so?

No matter how you analyze the data from field notes, to video to personal observation (been there, seen that) the answer to the three questions listed above are:

1) No, chimpanzees in the wild do not avoid attacking others if they appear to have a numerical advantage over their rivals. Goodall suggested this in her classic volume on the Gombe chimpanzees and it has since been supported through observational (Sherrow & Amsler, 2007) and experimental (Wilson et al, 2001) work.
2) Yes, chimpanzees in the wild exhibit behaviors (and physiology) associated with excitement when they attack others. Their hair stands on end in what ethologists call pyloerection and they run around screaming and shouting, often displaying and seeking each other out for reassurance (personal observation).
3) Yes, when chimpanzees in the wild attack others they kill them when possible, or they attempt to do so. There have now been reports from every major chimpanzee research site, with long-term habituation of either lethal aggression or attempts to commit acts of lethal aggression (Boesch et al, 2007; Sherrow, in preparation; Wilson & Wrangham, 2003).

“Is murder common among wild chimpanzees?” I call this the anthropogenic question. Chimpanzees may kill each other, but murder is a wholly human act, it implies intentions, motivations and emotions that we cannot attribute to even our closest living relatives. As for the question of whether or not they kill each other, see #3 above.

“Do male chimps (and their cousin male humans) have “killer” “demonic” instincts towards their fellows?” I call this the disassociated question. “Killer” and “demonic” need not be inseparable in our understanding of the two words. A soldier who kills in defense of her/his country, or a police officer who kills in defense of victims of a violent crime are not considered “demonic”, yet they are killers by the strictest definition of the word. They are also something else – heroes. Killing, in most human societies, is not always bad, but depends on the context of the killing (Livingstone Smith, 2009).

Dr. Narvaez chose to use the term “demonic” because of a very influential and popular book that was published in 1996, Demonic Males: Apes and the Origins of Human Violence by Wrangham & Peterson. In that book the authors used solid data (science lingo for information) on the living apes to show that when violence and aggression occur in our non-human cousins, males are the primary actors. In other words, males in our closest non-human ape relatives; bonobos, chimpanzees, gorillas and orangutans are more violent than their female counterparts. To those of us who study apes, this book was not as surprising as it was a great job of compiling and synthesizing much of the known information about apes at the time.

One of the most controversial claims made by Wrangham & Peterson in Demonic Males, is one that has been made by Dr. Jane Goodall, DBE herself and has been supported with overwhelming evidence from across Africa (e.g. Arcadi & Wrangham, 1999; Boesch et al, 2007; Goodall, 1986; Mitani et al, 2010; Muller, 2002; Nishida, 1979; Sherrow & Amsler, 2007; Watts et al, 2006; Williams et al, 2008; Wrangham, 1999), chimpanzee males regularly patrol territorial boundaries and when possible attack and kill males and infants from other communities.

Dr. Narvaez, uses information from two books by Hart and Sussman (2009) and Power (1991), which she claims to show how the evidence for lethal xenophobia in chimpanzees, presented in Demonic Males is “paltry”. She even uses the arguments laid out by Hart and Sussman to establish her position:

“(1) Goodall reports a so-called raiding party in 1982 in which a female was chased and mildly attacked and her 4-year-old son was sniffed.”
– Dr. Narvaez does herself a disservice by using the term “so-called” in describing the report by Goodall from 1982. Dr. Goodall literally wrote the book on chimpanzee behavior.

“(2) A 35 year old male’s body was found in 1981. With no evidence, murder was inferred. Males rarely live past 33.”
– The body had been trampled with injuries that appeared to be from other chimpanzees. Beyond that, again, chimpanzees do not “murder”. While the average age for male chimpanzees at death is around 33 that includes males who die before age 15. Once males reach maturity, they can live into their late 30’s and 40’s in the wild.

“(3) “From 1970 to 1982 six adult males from one community disappeared at a Japanese study site in the Mahale Mountains of Tanzania, west of Gombe,” one by one over a 12 year period. With no evidence, murder was inferred. But lions are common predators of chimpanzees in that region.”
– While the attacks weren’t observed in those cases at Mahale, the males in question disappeared after intense territorial disputes between two communities and extremely loud and violent fighting sounds were heard before those males disappeared (Nishida et al, 1990). Again, “murder” was never inferred. As for lions being “common” predators of chimpanzees in that region, that statement is misleading. Lions regularly pass through the Mahale study area in western Tanzania and do prey on chimpanzees, however they are not common predators. Further, if lions were regularly eating chimpanzees in the region, we would expect to see a consistent rate of predation and it should be fairly evenly distributed between males and females (in fact, given that females are often alone, it should skew toward more females being preyed upon). Instead, the disappearance was of adult males, after intense territorial interactions.

“(4) Wrangham and Peterson misreport statements by Christopher and Hedwige Boesch, saying that they said “violent aggression among the chimpanzees is as important as it is in Gombe” whereas they really said, according to Hart and Sussman is that “encounters by neighboring chimpanzee communities are more common in their site than in Gombe and that this may lead to larger, more cohesive, group structure and a ‘higher involvement of the males in social life’-there is no mention of any violence or killing during these encounters” (p. 210).”
– This is just plain wrong. What Boesch and Boesch (1989) really said was, “The pressure of territorial fights could be another major factor. Encounters with neighboring communities are fairly common (29 encounters in 29 months in Tai’). It might well be that the larger a male group is, the higher is its chance to win such territorial fights and the higher is its chance of enlarging its territory and its access to females (see descriptions of intercommunity encounters in Gombe;Goodall,1986;Wrangham, 1975)…This increase in group cohesion may be related to an increase in territorial pressure from neighboring communities. Thus the probably higher rate at which strangers are encountered in Tai’ may have forced them to adopt a more cohesive group structure, which may subsequently lead to a higher involvement of the males in social life at the cost of tool manipulation (Boesch and Boesch, 1984b).” Territorial fighting, by definition, is violent.

(5) At the site Wrangham had studied since 1984, a male’s body was found in 1991 a few days after the troop’s males had been exchanging calls with another community. The researchers had not seen any violence, nor was there any in the 7 years prior or 6 years after the incident. With no evidence, murder was inferred.
– Again, this statement, like the last is wrong. First, the chimps name was Ruwenzori, not Ruizoni as Hart & Sussman claim (p. 210). He was named for the mountain range to the west of Kibale National Park, where he lived and his body was found four days after he went missing, after an intercommunity encounter (a shouting match) between his community and their neighbors to the south. The research team “…found his disintegrating body hunched at the bottom of a little slope. The trampled vegetation bore witness to a struggle that started upslope and careened downward, sometimes sideways, for fifteen meters or more. Ruwenzori’s body was bitten and bruised and torn. He died healthy, with a full stomach, on the edge of adulthood, on the edge of his range.” (Wrangham & Peterson, 1996. p20). This is substantial evidence that Ruwenzori was killed by other chimpanzees, not “no evidence” as Dr. Narvaez would have her readers believe.

It’s unfortunate that Dr. Narvaez didn’t take the time to dig a little deeper into this subject, or to use information from researchers who study chimpanzees. While I don’t think you have to study chimpanzees to understand their behavior, and that you can get a lot from the literature, I think that something can be said for first-hand experience. Once you witness lethal violence in chimpanzees, you are not likely to forget it. For those with strong stomachs I have attached a short video to this blog that will hopefully provide some understanding to the excitement and brutality involved when male chimpanzees stalk other chimpanzees and engage in lethal violence towards them.

By not going deeper into the argument, but instead using some of the data to support a position she already holds, Dr. Narvaez is being ignorant at best, and more likely irresponsible in her blog. When Dr. Narvaez claims, “…that our current cultures, societal practices and beliefs have created the violent humans we see around us. They are an aberration from our evolutionary heritage…That means we have ourselves to blame, not selfish genes, not evolution. And it means we can change the practices and beliefs that create our violent cultures.” She is stating a philosophical position that is admirable in some regard, but not defensible given the information out there on chimpanzees and humans.

The other day in my Human Evolution course I had my students go through an exercise of identifying and labeling the traits that make us human. We listed everything we could think of and then went through them all, crossing them off to get at the traits that were unique to humans. One of the traits the students came up with was “lethally xenophobic”, referring to the propensity of humans to attack and kill members of other communities, nation states, ethnic and religious groups. The students were quick to point out that that trait was not unique to humans, but like our chimpanzee cousins we form in-groups and out-groups, and like our chimpanzee cousins we are not kindly disposed to members of out-groups, or outsiders.

By ignoring what the scientific data tells us about ourselves and our closest living relatives, we are committing ourselves to an inquiry of ignorance that is doomed to failure. If we want to succeed in understanding violence and warfare, we must understand its evolution.


Arcadi, A. C. & Wrangham, R. W. 1999. Infanticide in chimpanzees: Review of cases and a new within-group observation from the Kanyawara study group in Kibale National Park. Primates. v40 (2). p337-351.

Boesch, C. & Boesch, H. 1989. Hunting behavior of wild chimpanzees in the Tai National Park. American Journal of Physical Anthropology. v78. p547-573.

Boesch, C., Head, J., Tagg, N., Arandjelovic, M., Vigilant, L., & Robbins, M. M. (2007). Fatal chimpanzee attack in loango national park, gabon. International Journal of Primatology, 28(5), 1025-1034.

Goodall, J. 1986. The chimpanzees of Gombe: Patterns of behavior. Harvard University Press.

Livingstone Smith, D. 2007. The most dangerous animal:Human nature and the origins of war. St. Martin’s Press.

Muller, M. N. 2002. Agonistic relations among Kanyawara chimpanzees. In: Behavioural diversity in chimpanzees and bonobos. Cambridge University Press.

Nishida, T. 1979. The Social Structure of Chimpanzees of the Mahale Mountains. In: The Great Apes. Ed Hamburg, D. A. & McCown, E. The Benjamin Cummings Publishing Company.

Nishida, T. 1990. The Chimpanzees of the Mahale Mountains: Sexual and Life History Strategies. The University of Tokyo Press.

Sherrow, H. M. & Amsler, S. J. 2007. New cases of inter-community infanticides by the chimpanzees of Ngogo, Kibale National Park, Uganda. International Journal of Primatology. v28 (1):9 – 22.

Sherrow, H. M. In Preparation. The Testicle Targeting Hypothesis and Intrasexual Competition Among Male Chimpanzees. To be submitted to Behavioral Ecology & Sociobiology.

Watts, D. P., Muller, M., Amsler, S. J., Mbabazi, G., & Mitani, J. C. (2006). Lethal intergroup aggression by chimpanzees in kibale national park, uganda. American Journal of Primatology, 68(2), 161-180.

Williams, J. M., Lonsdorf, E. V., Wilson, M. L., Schumacher-Stankey, J., Goodall, J., & Pusey, A. E. (2008). Causes of death in the kasekela chimpanzees of gombe national park, tanzania. American Journal of Primatology, 70(8), 766-777.

Wilson, M. L., Hauser, M. D., & Wrangham, R. W. (2001). Does participation in intergroup conflict depend on numerical assessment, range location, or rank for wild chimpanzees? Animal Behaviour, 61, 1203-1216.

Wilson, M. L. & Wrangham, R. W. 2003. Intergroup relations in chimpanzees. Annual Review of Anthropology. v32. p363-392.

Wrangham, R. W. 1999. Evolution of coalitionary killing. Yearbook of Physical Anthropology. v42. p1-30.

Wrangham, R. W. & Peterson, D. 1996. Demonic Males: Apes and the origins of human violence. Houghton Mifflin.

Primates are smart, even the “dumb” ones. When I say the “dumb” ones, I mean those that score lower on our measurements of intelligence and have smaller brains relative to body size than species that we usually consider very bright [e.g. capuchins, chimpanzees, bonobos, spider monkeys, etc…]. Despite being the “dumb” ones, these primates have bigger brains and score higher on measures of intelligence than most other mammals species. As an Order, Primates have big brains, live in complex social worlds, and eat food that is often widely dispersed and unpredictable [except for some folivores]. They rely heavily on learned behavior for everything from finding food to finding mates, devote a lot of energy to single, or a few offspring at a time, and they take a really long time to grow up. In fact, primates have the longest pre-reproductive life history stages of animal mammal, including elephants and whales. This trait is most exaggerated in our own species, in which most females do not begin reproducing before the age of sixteen, and most males do not take on the characteristics of an adult male until the age of twenty, or so. Among the non-human primates, we see a similar trend, though it is nowhere near as extreme as is the one observed in humans. Even so, all of these factors and traits combine in our biological Order to result in extremely long lived, slowly maturing organisms that spend a lot of energy trying to successfully raise one offspring at a time and have great big brains. The end result: Primates are smart, even the “dumb” ones.
Having said all of this, the question remains, how do we know primates are smart? To answer that question, we have to know just what “smart” is. In other words, we have to find a good measure of intelligence. Intelligence usually refers to the intellectual capacity of individual, which in many cases simply means their ability to reason, or comprehend a situation, to problem solve. The problem with this definition, and attempts to measure this kind of intelligence in non-human primates is that this is a very human definition of intelligence. Reasoning, comprehension and problem solving are all mental characteristics that are important to the survival and reproduction of humans. The end result is that intelligence is only measured in an anthropomorphic way. We have very few, if any purely objective measures of intelligence, which are not put in a human context. While these are, usually, useful for understanding how smart animals are relative to us, they may not tell us how smart they actually are. For example, an animal’s ability to solve a human constructed problem may have nothing to do with its ability to survive and find mates in its natural habitat. So, the questions should be posed: Does intelligence exist outside of the human construct? If it does, is it important to other animals, and how can we measure it objectively? While there has been a lot of work on this over the last few years, completely satisfying answers have not yet emerged. Instead of recapping them here, I would like to hear what you all have to say. What do you think intelligence is? How should it be defined and studied? Does it matter?