In this review, the authors explore the idea of Hamiltonian Medicine (HM). The driving force behind this idea is Hamilton’s theory of inclusive fitness, which incorporates the fitness of an individual and the effects said individual has on those that carry genes identical to the individual’s via descent. The authors argue that this is a theory that is widely accepted by the thinkers and practitioners of Darwinian Medicine (“the application of evolutionary concepts and tools to understand health and the causes and treatments of disease”), but is not systematically used as it ought to be in a number of contexts. Thus, the goal of their review is to show how HM can provide insights that have been missed/overlooked in the current Darwinian Medicine mode of thought. First, they describe three domains of social relationships covered in the scope of HM: 1) interactions between cells 2) interactions between genes and 3) interactions between humans. They then go on to describe six principles of HM, which all focus on the impact that interactions within and between the three aforementioned domains can have on human health. One example is the relatedness between microbes and the effect that this can have on virulence and transmission. This type of interaction also is dependent on how their hosts, in this case humans, behave, and thus the two domains of relatedness overlap to have a compounded effect on human health. They also point out how intragenomic conflicts and resource conflicts can have profound effects not just within societies but also within individual families. And lastly, they point out new ways of thinking about diseases such as cancer and mental illness. For example, cancer cells exhibit many similarities to microbes in an HM context, which could offer new perspectives from which alternative treatments might found. As a whole, HM seems to offer a very cohesive and profound insight to understanding human health in an evolutionary context. One of the challenges, which the authors mention, is that pursuing this kind of thought and research is going to be incredibly difficult and involved, because of the complex and interdisciplinary nature of this branch of thought and practice. Thus it will take time and experimentation for HM to effectively put into practice and to become a major branch of research. But, it seems that the knowledge and understanding that could come from pursuing it would be well worth the investment – as long as adequate funding and organization go into it.
Babies have a tendency to cry at night, much to the dismay and frustration of many a parent. There are many reasons for why this might be: the baby is hungry, cold, wet, just wants to be held, someone made a noise that woke them up. However, a recent study described in a Science News article provides another reason for why this nighttime crying occurs: it prevents the baby’s mother from getting pregnant again.
Evolutionary biologist David Haig proposes in the past, babies that cried at night had a better chance of survival. This is because the constant interruptions have multiple effects on the mother, many of which act as a kind of birth control. In addition to interrupting potential late-night liaisons and making the mother exhausted, regular nighttime breast-feeding causes hormonal changes in the mother that can delay ovulation (though this is not a foolproof contraception method). Combined, these results of nighttime crying reduce the chances of the mother getting pregnant. How does this relate to the baby’s survival? The answer is simple: if the mother is not devoting resources to another child then the baby will receive more attention and care from the mother during a very vulnerable stage in life. Thus the baby will be more likely to survive its early childhood, and therefore be more likely to reach reproductive years during which it can pass on its genes to offspring.
While many point out that babies crying at night is caused by a number of other factors, Haig’s proposal provides a new evolutionary significance for the phenomenon. Not only can nighttime crying be seen as sibling rivalry, as the baby is trying to avoid having more siblings for as long as possible, but also shows an example of the battle between sex-linked genes. Male genes tend to cause behaviors that will result in the passing on of genes to the next generation, regardless of the cost to the mother- which explains why male babies have a tendency to cry more at night than females, because there is no guarantee that the mother’s next baby will carry the male’s genes. However, females carry certain genes that tend to make them sleep longer at night as babies, which acts more in the interests of the mother who wants to have more energy to care for her young. Additionally, Haig points out that nighttime feeding is not actually necessary for the baby in our modern day society where most babies have access to adequate nutrients, which supports the idea of nighttime crying being a clever, though unintentional, survival strategy of babies – and also means that moms don’t need to feel too bad if they skip a nighttime feeding session or two.
I came across an interesting article called “Odd Cause of Humans’ Dark Skin Proposed”, which states that skin cancer could have directly driven evolution of dark skin in humans. According to the study, people who have albinism, which is an inherited disorder that prevents human from making black or brown pigments, almost die of skin cancer at young ages. The study suggests that the early death of albino people might be the reason why early humans evolved dark skin.
Individuals with white skin are more vulnerable to skin cancer than people with dark skin. For instance, the Skin Cancer Foundation reported that black or brown pigmented skin has a sun protection factor of 13.4, which is relatively higher than that of the white skin (3.4). When hunter-gatherers began to lose their body hair to keep their body temperature cool during their excessive movement for hunting and gathering, they probably had light skin similar to the chimpanzees that has white skin under their fur. However, the article stated that humans evolved to have dark skin about 1.8 million years ago, then evolved light skin again after they migrated to higher latitudes from Africa.
The paper mentioned that skin cancer itself could have driven humans to have dark skin. In addition to the fact that the probability of developing skin cancer is significantly higher for albino people than for people with darker skin, almost all albino people in Africa developed skin cancer at early ages due to high prevalence of outdoor labor. These early cancers in lighter skinned humans lead them to die before reproduction, thus leaving mostly darker skinned individuals to pass on their genes to next generations. Although this idea is still hypothetical, it was interesting to see that cancer can influence human evolution.
I think we all understand the idea of how to trace HIV transmission – by sequencing the viral genomes of different strains and looking at differences, we can map the phylogeny of the different strains. In doing so, we can see who infected who. Here’s an article that summarizes this pretty well.
I thought this was pretty cool because when HIV-positive individuals are told about using condoms and how that prevents infection of HIV-negative individuals – but less often do you hear about preventing transmitting another strain to an already HIV-positive individual. The consequence of infecting an already infected individual is introducing, to some extent, a new virus. Depending on viral loads, re-infection might actually change the viral population dynamics and introduce new mutations and phenotypes to the viral landscape in the individual. The primary consequence of this is that re-infection may lead to drug resistance and dramatically affect treatment course.
I didn’t know to what extent this idea of super-infection was known among the population, but this study shows that the possibility is actually very well known. While this all seems pretty logical and understandable, I can’t help but think about what this means in the realm of public health – How does this affect how health professionals counsel people living with HIV/AIDS (PLWHA)? Should we treat couples together, regardless of HIV status? Should we sequence strains to see where individuals were infected and use that to develop specific prevention strategies?
I remember hearing about something like this before and found it both ironic and slightly disturbing. Some patients who were admitted into hospitals ended up acquiring these infections they did not have when they went in. This happens in about 5% of hospital patients in the U.S. (or around 2 million cases a year). These hospital acquired infections (HAI) kill around 90,000 people a year. This can be quite disturbing since many of us picture hospitals as these clean sanitary places with everyone wearing masks and gloves for protection. These infections are caused by viral, bacterial, and fungal pathogens. The idea here is that hospitals are essentially a gathering place for all of these diseases. There are 3 categories of risk factors for acquiring HAI.
“Iatrogenic risk factors include pathogens that are present on medical personnel hands, invasive procedures (eg, intubation, indwelling vascular lines, urine catheterization), and antibiotic use and prophylaxis. Organizational risk factors include contaminated air-conditioning systems, contaminated water systems, and staffing and physical layout of the facility (eg, nurse-to-patient ratio, open beds close together). Patient risk factors include the severity of illness, underlying immunocompromised state, and length of stay.”
With these people being in so close a proximity to each other, it makes it easier for the pathogens to move around and therefore infect more people quickly. These people will also be exposed to pathogens they may not have gotten if they did not go to the hospital. It’s actually kind of strange really. Hospitals were developed to try to help people as efficiently as possible, but they do have their problems. I’ve helped out at a hospital before and worked on ambulances. They work very hard to make sure everything is as sanitary as possible for both the patients and staff. However, it is still possible for pathogens to get around. I guess it just shows how persistent (and annoying) they can be.
An article I read looked at a study published in Evolution, Medicine and Public Health, proposed an evolutionary reasoning as to why babies cry at night. The research proposed that babies consciously or unconsciously cry to their mother to prevent the birth of a new sibling that would ultimately end up mean competing for resources, and subsequent survival. Apparently this sort of behavior does have an effect on mothers: nursing a child, especially at night, can stop women for resuming ovulation as essential for reproduction. In this case, the baby is somehow employing a “survival of the fittest” mentality. Of course, many doctors do not agree, and argue that on the contrary, the nightly breast feeding may be cooperation as both baby and mother may benefit nutritionally and in terms of general health.
I personally jumped to Bonita’s presentation today about possible evolutionary theories behind anxiety, and I think the basis of attachment theory – the attachment a child has for his or her mother – causes anxiety may be the only basis of the child’s crying. It may be an anxiety of an inset fear of being separated from the mother, even if she is nearby that could cause crying fits, and as a child matures that anxiety is quelled with logic and understanding. Otherwise, looking at the theory proposed by the study, I do not see why a baby would EVER stop crying even after it matures into a child or older, at least until 15 or 16. Up to that point, it would still have a certain concern of competing for resources or attention and would not stop crying at night until it no longer was dependent on the mother for resources or survival. Of course, I am not an evolutionary biologist, so the theory might not be as ridiculous as it sounds to me, but I would personally need to see a LOT more research before I believed this one.
The article, “How is Darwinian medicine useful?”, written by Randolph M Nesse caught my attention, because it emphasized the usefulness of evolutionary principles in medicine. I think it is appropriate to post a blog about this article, since it is very relevant to our course in understanding evolution in sickness and in human health.
Evolutionary medicine uses an evolutionary perspective to learn why our body is not perfect and why diseases exist in human population. The article lists main principles of Darwinian medicine for explanations to these questions. One of the examples that the paper mentioned is that the obesity and its associated problems arise because our body is not designed to live in the modern environment. Natural selection shaped human appetite regulation mechanism in order to survive the periods of famine based on the environment in the ancient times. Another example the author mentioned is the usefulness of human defense systems. Pain, nausea, cough, fever, vomiting, diarrhea, fatigue, and anxiety are all common defense mechanisms. These are not problems of themselves but it is an attempt to cure a problem. In addition, the paper explores the reason why humans are vulnerable to certain diseases. One main reason stated is that natural selection is a random process with no direction. Moreover, the purpose for the natural selection is not to make an organism either perfect or healthy, but to maximize reproduction.
The paper emphasizes that the evolutionary view offers a richer view of the human body as a product of natural selection. I agree with this statement, and I believe evolutionary medicine will advance our understanding of the pathogenesis of various diseases. In addition, health professionals will be able to find more effective treatments by understanding why people get the disease rather than by simply considering how they get the disease.
I posted something about psychology before, but never got into too much detail about it. I did my presentation today about anxiety disorders and we also talked a little bit about personality disorders. During class we talked about the new DSM-V for mental disorders. The development of this book is particularly interesting to me because it shows how time, people, and society changes our views on mental disorders. It was not long ago that homosexuality was diagnosed as a mental disorder and has now been removed. The reason I find this manual so fascinating is because it looks into the cognitive side of medicine and not focussing on biology alone. I know this is a biology class, but mental disorders and psychotherapy fit into medicine as well.
With the new book out, there has been some new changes that have sparked controversy among the field. One of them is the constantly changing criteria for illnesses, new illnesses added or removed, and just things being reorganized. However, this manual does have to evolve has new information is found and societal views change. Like I stated before, homosexuality was classified as an illness and is now removed. Medicine and medical practices have been updated regularly as new information is found so it stands to reason that the DSM change as well.
I suppose one of the biggest issues with mental disorders are they are hard to define and people have different ideas on causes and who has it and who doesn’t. I believe this statement from NIMH director Thomas Insel said it best:
“The weakness is its lack of validity. Unlike our definitions of ischemic heart disease, lymphoma, or AIDS, the DSM diagnoses are based on a consensus about clusters of clinical symptoms, not any objective laboratory measure. In the rest of medicine, this would be equivalent to creating diagnostic systems based on the nature of chest pain or the quality of fever.”
The proposed definitions for psychiatric disorders in the new manual were too broad and ignore smaller disorders that were lumped in with a larger diagnosis. Although one could argue that pinning down a disorder is hard on it’s own. One person may say you have this, but when you go to someone else, then you get a completely different diagnosis. There are few clear cut lines in mental illness, which is why I believe more research needs to be done. While some may think mental illness like depression are just something you can get over, this is not true and to fully understand it means we must learn more about illnesses and maybe improve the DSM to help with diagnosis.
Interestingly, I saw an article that actually ended up startling me than giving me the confidence I had hoped. According to a survey, most Americans are skeptic of evolution rather than having confidence in it as a concept. 31% of respondents said they were very confident that “life on earth, including human beings, evolved through a process of natural selection” whereas 42% said they were not at all confident. These results are surprising to me as I had largely hoped that Evolutionary medicine would be a part of undergraduate education. I had always known that evolution was a controversial topic, especially growing up in the South, but it surprised me just how much of a majority of Americans have no confidence at all. This makes it tough in the trajectory of Darwinian Medicine being implemented into medical practice, as the essential framework of the practice could contradict the beliefs of a large portion of Americans.
The article continues to highlight that these numbers are due to politics and religion, where once more science seems to be at odds with faith. Further, it also highlights that the implications of this rift are that many children will not be vaccinated and spread diseases because of the generalized distrust of certain scientific concepts. In the same survey, 15 % of Americans said they were not at all confident that childhood vaccines were safe and effective and 30% were not sure. 15% may not seem like a lot, but considering the number of Americans that amounts to it is a much larger number than I expected.
These sorts of differing views on evolutionary concepts may make it much tougher for evolutionary biologists and supporters of Darwinian Medicine to see their visions implemented in American education.
Poll shows Americans not confident Big Bang, climate change or evolution is real. (n.d.). CBSNews. Retrieved April 24, 2014, from http://www.cbsnews.com/news/americans-big-bang-evolution-ap-poll/
For my last blog post, I thought it would be appropriate to reflect on this course and the significance of evolution in the broader context of medicine and drug development. In his Huffington Post article, Steven Newton briefly explains five reasons as to why evolution is an essential component of modern medicine. The five areas of medicine where evolution plays a critical role (in Newton’s list) are: H1N1 and emerging diseases, HIV, vaccines, antibiotic resistance, and drug development. While the notion of evolution may conjure an image of a slow process, this article demonstrates otherwise. Four of the five topics that Newton mentions emphasize how rapidly evolution can occur and how it mandates the development of new treatments, vaccines, and antibiotics.
On a deeper level, however, this article is particularly relevant to this course as many seemingly ‘obvious’ statements that Newton mentions now carry a deeper evolutionary meaning and context with them. For example, when Newton mentions how ‘rapid evolution combined with rapid travel’ can lead to the spread of a disease, I am reminded of our class discussion on how human behavior and rapid transportation have facilitated the transmission of many infectious diseases. Furthermore, Newton’s reference to how a ‘multi-drug’ approach is better suited for HIV treatment (due to the virus’ rapid evolution) reminds me of Dr. Goldberg’s lecture on cystic fibrosis (CF) and how drug cocktails have been used to treat patients with CF. The article’s discussion of the importance of vaccines and the mechanisms behind how they work serves as a reminder of Dr. Mina’s lecture on LAIVs and the common misconceptions associated with vaccines. Additionally, Newton’s discussion of how antibiotics can “[wipe] out almost all [of an individual’s] bacteria” reminds me of Justine Garcia’s lecture on the critical role that the microbiome plays in health and disease outcomes. And lastly, Newton’s reference to drug development and the use of animal models serves as a reminder of our discussion on personalized medicine and the inaccuracies associated with animal model testing. Thus, by fortifying our understanding of fundamental evolutionary principles and by providing us with a plethora of examples of how evolution shapes modern medicine, this class has equipped us with a deeper insight and appreciation for Evolutionary Medicine and its wide applicability to the past, present, and future of medicine.