The genome of the tsetse fly has recently been sequenced and the success has been gaining attention in mainstream media through the New York Times and National Geographic. Why is the tsetse fly important and what’s so special about its genome? The tsetse fly transmits human African trypanosomiasis, commonly known as “sleeping sickness.” Trypanosomiasis is a vector-borne parasitic disease with two main types, depending on the parasite (Tranosoma brucei gabiense causes 98% of cases, trpanosoma brucei rhodesiense causes the other 2%). Trypoanosomiasis occurs in 36 Sub-Saharan African countries where tsetse flies are found. Animals can also be affected by tyrpanosomiasis, and can serve as reservoirs for human pathogen parasites. Thus, animal husbandry is more difficult in areas with tsetse flies, which are mostly rural.
There are many interesting discoveries about tsetse flies that have been made in the process of sequencing its genome. For example, female tsetse flies give birth to one larva at a time and only produce about 8-10 offspring during their life span, unlike mosquitoes that can produce about a thousand offspring. Therefore, eliminating one female tsetse fly can have a big effect on the population, according to Dr. Serap Aksoy of the Yale School of Public Health. Even though tsetse flies feed on blood, females nourish their young in the womb with milk, a surprising characteristic that somewhat resembles mammalian care for offspring.
The Aksoy lab at Yale is responsible for sequencing the tsetse fly genome. They hope that this will aid current control methods and lead to the development of new strategies to reduce or even eliminate the transmission of trypanosomiasis in Sub-Saharan Africa. One line of attack is targeting the single gene that regulates milk production in female flies. The idea is that less milk will cause the flies to be less fertile. Other possibilities are vaccines and/or repellants that target specific aspects of the tsetse fly genome.
A comical article asks, “Are beards about to die out?” in reference to a recent study examining the frequency-dependent selection of bearded men. According to the article, beards have become very popular lately, but their current popularity will soon make them less attractive.
Though beardedness is a physical trait, it is determined by behavior—shaving or not shaving—rather than solely through genes (frequency-dependent selection is usually studied in organisms like guppies and butterflies with polymorphic color variations). Yet, the same fitness concepts may apply to a behavior if it influences the attraction of potential mates.
This study is unique, because it didn’t simply investigate whether or not people found beards attractive; it measured the attractiveness of beards in multiple frequency contexts. In the experiment, 36 men agreed to grow beards and photographs were taken of them at four intervals of the growth period under identical lighting conditions. The photographs were presented to 1453 women (heterosexual or bisexual) and 213 men (heterosexual). The researchers organized the photographs into multiple contexts ranging from mostly bearded to mostly clean-shaven.
The study found that the attractiveness of beards does fit the model of negative frequency-dependent selection: in the mostly clean-shaven groups, beards were rated about 20% more attractive, but when beards were more common, clean-shaven faces were rated with a similar spike.
This research gives an evolutionary explanation for the cycles of popularity for physical features and clothing. It’s not suggesting that beards will disappear forever due to over-popularity, but it does show that traits are likely to be less attractive when they become too common in a population. This article gave me a new perspective for what it means to be “hipster.”
This article explains the findings of a recently published research that found that Europeans inherited three times as many lipid catabolism genes from Neandertals than Asians did. This is a development that has come out of the extensive comparison of Neandertal and modern human DNA that ensued after researchers at the Max Planck Institute sequenced the Neandertal genome. Researchers have found that Neandertals interbred with modern humans at least once in the past 60,000 years, before their extinction 30,000 years ago. This interbreeding occurred after the decent from Africa; so, traces of Neandertal DNA are not found in Africa DNA, but have been detected in European and Asian DNA—an average of about 1-4%. There is even evidence that different populations of living humans inherited Neandertal genes that may cause diseases like diabetes and Crohn’s, alter immune function, and affect the function of keratin.
According to this research, Northern Europeans have differences in fatty acid composition and in enzymes that metabolize fat in the brain that are traced to Neandertal DNA. Kaitovich and other researchers involved with this study are not sure how these differences affect the brain, but they “think it’s a very strong effect with very profound physiological changes. Otherwise, we wouldn’t see it in the brain tissue.”
Since the fatty acid genes are found in a much higher percentage in Northern Europeans than in Asians, Khaitovich hypothesizes that they were advantageous for modern humans in adapting to colder environments. These findings suggest that one type of human could take an “evolutionary shortcut” by inheriting an advantageous gene from another group, such as the Neandertals, through interbreeding. However, now, these genes are thought to be somewhat disadvantageous for contemporary humans as they are associated with obesity, diabetes, high blood pressure, and cardiovascular disease.
I do not have a background in Anthropology, so I was surprised to learn about the interbreeding of Neandertals and modern humans. Others may be able to provide more insight for the background of this research. I am interested to see what other implications about human health arise from further investigation of these ancient genes.
In class we have touched on the issues surrounding research progressing from animal models to human subjects and we have discussed the possibilities that personalized medicine and the human genome project pose for the future of health care. Gene therapy , in which researchers continue to search for effective but safe vectors to introduce the DNA of “healthy” versions of genes into diseased patients, is highly related to these discussion topics. This technique offers a huge range of possibilities for countless genetic disorders, but it has many associated complications as well.
This article (accessible through Emory’s network) outlines the troubled past of gene therapy, its setbacks, current research being conducted in the field, and the future of the therapy. Until reading this article, I was unaware of the rocky history of gene therapy. I deemed this important to share with the class so that we would all have a more holistic view of a this development in medicine that has the potential to be viewed through a singular, highly optimistic lens.
Upon reading the gene therapy article, I investigated the death of Jesse Gelsinger and came across this NY Times article about his death and the research study that caused it. This story is a grave reminder of why there are so many regulations in medical research, and that even when everything seems to have been done properly there are still occasionally unpredictable outcomes.
I am interested in following the advancement of gene therapy in the upcoming years, especially since new techniques are expected to be approved in the U.S. by 2016. Gene therapy has the potential to drastically change the way we treat many diseases, but we must not forget the history behind it.
The other day in class we were introduced to Nikolaas Tinbergen‘s four questions during our discussion of proximate and ultimate causation. Tinbergen is also known for conducting research on “Supernormal Stimuli” in animals. A supernormal stimulus is defined as a stimulus that elicits a response stronger than the stimulus for which the response mechanism evolved. The blog post, Is Your Brain Truly Ready for Junk Food, Porn, or the Internet? connects Tinbergen’s research on supernormal stimuli in animals to that in humans with the help of a comic by Stuart McMillen, a Youtube video about Nicholas Carr’s research on the effect of the Internet on the human brain, and Diedre Barret’s book Supernormal Stimuli: How Primal Urges Overran Their Evolutionary Purpose. Modern day examples of supernormal stimuli for humans are: junk food, the Internet, pornography, TV, and video games.
I found this topic interesting because I am familiar with the tendency of our bodies to crave junk food based on what was evolutionarily valuable for our species to consume in the past, but I had never given much thought about how our minds may develop addictions to technology based on our evolutionary background. Humans have created their own supernormal stimuli by manufacturing foods that are sweeter and more calorically dense than naturally occurring foods, TV shows and video games that provide us with the ability to enter a world that may be deemed “better” than actual reality, pornography that tends to exaggerate sexual acts and the human body (which does not seem to be a new thing for humans based on the discovery of the Venus of Willendorf), and the Internet which provides access to endless information/entertainment/distraction at the tips of our fingers.
The blog post concludes by providing encouragement that humans are not inevitably doomed by our new environment. Unlike the animals in Tinbergen’s research, humans can differentiate between reality and supernormal stimuli. Humans have the ability to take control of their actions and moderate their indulgence in these behaviors. Could the ability to regulate the time and energy invested in surfing the Internet, watching porn, or playing video games serve as a factor of natural selection in present-day humans?