All posts by Grace Yang

Are we forcing animals and plants to evolve with us ?

Evolution is a dynamic, interactive process that occurs constantly in nature, however, in a sense, humans have had disproportionate influence on evolution of other species thanks to the development of technology that allows us to achieve effects that animals in nature could not have accomplished. I think this is a very interesting article because we have read about how human interactions with the environment have changed pathogen transmission patterns in class, and this article provides more evidence that we might not be aware of.

12,000 years ago, domestication of wolves into dogs. Humans have domesticated all kinds of animals. Now days, the industrial, massive way humans fish is causing marine species to evolve to reproduce at younger ages and smaller sizes in order to keep passing on their genes. More specifically, cod, which have been overfished for decades off New England and the Canadian Maritime Provinces, have begun reproducing at younger ages and smaller sizes. Other species that have been observed to shower similar changes are bighorn sheep, caribou and ginseng plants. The shift in reproductive pattern improves the chances of reproducing before being killed, which gives those animals a short-term survival advantage. But it is harmful for the them in the long run, according to Paul Paquet, an environmental scientist at the University of Calgary, because the smaller, younger offsprings are not as strong and healthy as the older and bigger ones. Consequently, they are less likely to survive on their own. He refers to this phenomenon as “forced evolution”. As a result, Maine has passed legislation to protect lobsters and other common fish species from being hunted at a young age.

In addition, climate and landscape change have altered animal and plantation’s living environment beyond our estimation. For example, the development of highways and deforestation have physically limited the habitats of many wild animals and decreased their offsping’s diversity, which is detrimental for them in the long run. Furthermore, as a result of climate change, plantations shift their timing of bloom or move to a higher altitude in order to survive and reproduce.

The introduction of apples to North America in the 17th century led some fruit flies that had specialized on hawthorn fruit to branch out to apples instead. By the mid-1800s, the branched out flies have completely separated to form its own species. Further down the stream, that has encouraged modification of parasitic wasps that feed on those flies.

When we read about a specific study on a specific pathogen, the human impact on nature does not seem to be too detrimental. However, when we look at the bigger picture that include all aspects of ecosystem, humans have greatly altered the way animals and plants survive and reproduce in nature.


Dean, C. (2009, February 10). Seeing the Risks of Humanity’s Hand in Species Evolution. The New York Times. Retrieved from



A Second Look at Depression

The evolution of mental illness has always interested me, after our discussion in class about Schizophrenia, I became interested in the evolution of depression. Unlike Schizophrenia, depression is a common mental disorder, it is estimated to affect 121 million people all over the world and the number of people who have been diagnosed is increasing at a 20% rate per year. This phenomenon puzzles evolutionary biologists and psychiatrists because the alleles that are responsible for depression should be selected against over time according to the four postulates of evolution. This paradox is examined in this NYTimes article. 

The proximate cause of depression is rumination, which means that people fixate on their flaws and problems, and extending their negative moods, rumination decrease a person’s functionality in daily life and it is considered useless, waste of mental energy. Rumination is associated with ventrolateral prefrontal cortex (VLPFC), which is located a few inches behind the forehead. Interestingly, VLPFC is also responsible for intense focus which is necessary to produce meaningful work. Therefore, it is hypothesized that depression has the benefit to allow the individual to have an increased brain activity that normal people cannot achieve. In another word, depression is an extreme end at the spectrum of ordinary thought process, and the inability to engage in pleasant activities help the depressed person focus better on their work

The question is, does depression and sadness indeed make people more productive for being more attentive? Psychiatrists and researchers has argued that many patients who have suffered from depression have a hard time performing daily functions such as bathe or eat, not to mention work and solve problems. These counter arguments suggest that the benefit theory of depression is a stretch.

Another school of psychiatrists suggest that depression could be a warning sign like chronic pain. Only by seeing a therapists and walk through the rumination process, can patients who suffer from depression find out the fundamental cause of depression.

This leads to the conclusion from the author which I think perfectly describes the relationship between emotions and consciousness, “ This is the paradox of evolution: even if our pain is useful, the urge to escape from the pain remains the most powerful instinct of all.”

Synopsis (Greenspan)

The Greenspan paper sheds light on a topic that we have been focusing on since the beginning of class: how has modern medicine changed the evolution of human diseases? This author suggests that the development of modern medical technologies and vaccines has enabled human with rare diseases to live beyond reproductive age and pass on their genes; also, the improvement of living conditions has sustained tremendous population growth that gives rise to a larger gene pool that allows for possibilities of new mutations.Essentially, the cultural evolution has relaxed natural selection on humans.

 By using the example of Cystic Fibrosis, the author provides evidence that survival rate for the once-lethal disease has dramatically increased over the years and patients with CF can easily live up to reproductive age. In addition, the author uses empirical evidence to support the idea that a small mutation could easily be magnified into deleterious conditions.

 The authors distinguishes between culture evolution, which is the development of medical care and public health interventions; and biological evolution, which is the traditionally defined “survive of the fittest”. I think it is important to note that culture evolution is unique to human, so it is difficult to fit cultural evolution into the frame of traditional evolution theories. Also, I think the author brings up a great point that “personalized medicine” might be more challenging than we have expected due to the expanding population size and the weakened elimination on deleterious alleles.

Have Farm Animals Evolved with Us?

At the very beginning of class, we read an article by Wang that talked about how dogs have evolved with human as they are domesticated early on in their evolutionary history. In a recent class, we also discussed the differences in nutrition content between the meat we consume today and meat we used to consume decades ago. I was wondering if farm animals have also evolved with us as the domestication of chicken, cows, and pigs have definitely changed their physiology over the years.

In a NYTimes article, author pointed out that animals that are raised in modern industrial farms are bred to produce the most amount of edible meat. For example, chickens are bred to have gigantic, disproportionate breast because human like to consume chicken breasts. It is a desirable trait for human as meat consumers, however, it is detrimental to chicken’s health because large breast in no way benefit chicken’s survival or reproduction in their natural habitant. Human have genetically changed the way animals are raised in industrial farms, as a result, chicken eat less while grow bigger. However, physiology is not the only thing that has changed in modern farm animal population. Due to the highly regulated farm industry, farm animals tend to become more and more homogenized and loaded with antibiotics, consequently, they are a lot more vulnerable to diseases compared to their wild counterparts. Tyson Foods, which is called “America’s meat factory” that monopolizes the production of chicken, is able to bring chicken’s retail price from $6.48 per pond to $1.57 per pound, as a result of the mass production.

I think this phenomenon is best summarized by the author’s comment that industrialized faring “privatizes gains but socializes the health and environmental cost”.

Are Antibiotics Making Us Obese?

In the Scientific America article we read for class: Swapping Germs: Should Fecal Transplants ecome Routine for Debilitating Diarrhea, we learned about the importance of maintaining a healthy population of microorganisms in our gut. In previous classes, we also talked about the increasing health threat created by the overuse of antibiotics: the emerging new generation of bacteria that are resistant to all existing antibiotics.

I came across this NYTimes article that discusses the correlation between antibiotics abuse, obesity and microbiome in human gut. Essentially, it was discovered in 1948 that antibiotics makes young animals pack on weight easily. Since then, antibiotics have been used unethically as superfood to produce cheap meat. Another favor that antibiotics did for mass produced farm animals is that, they are able to stay inside for their entire life because they can now resist the terrible living conditions in animal farms while packing on more meat. The questions is, can antibiotics do the same thing to us? Could the American obesity epidemic be the result of our high consumption of antibiotics from both meat products and prescription pills?Despite of ethical limitations, an experiment was done on a group of children from Guatemala, while a doctor in Florida conducted similar experiment on a group of mentally challenged children. And just like they have expected, the children indeed grow larger just like farm animals. Although the exact causation of the weight gain from antibiotics is unknown, it is hypothezed that antibiotics can change the population of microorganisms in the gut and therefore change the metabolism of nutrients. As more studies are done on this particular subject, the correlation between microorganism population and human’s health and growth becomes more clearer.

Examining the history of antibiotics abuse not only reveals the health complications, but also sheds light on related ethical issues. While terminating the use of antibiotics from our lives all together is not realistic, we can choose to purchase farm raised, antibiotic-free meat product and try to find alternatives to all-purpose antibiotics in our prescription drugs.