Daily Archives: April 22, 2014

Hamiltonian Medicine Discussion

This article talks about Hamiltonian Medicine, which centers on the roles of genetic relatedness in human health and disease and represents the application of basic social-evolution theory, from interactions involving kinship, to core issues in medicine such as pathogens, cancer, optimal growth and mental illness. The 3 domains it incorporates are microbes or cancer cells within humans, genes expressed in humans, and human individuals. I feel that Hamiltonian Medicine is a great way to see and understand how evolution and medicine can work hand-in-hand. I enjoyed how they included that human social interactions, especially among relatives while individuals are young, appear to represent among the most potent and pervasive determinants of mental health throughout the lifespan, both directly and through gene-by-environment interactions. Sometimes I think people assume social interaction and mental health fall strictly under psychology, and I know some people who don’t think there’s any connection between psychology and biology, when this this is not true. Mental health can also be affected by genes and brain function, while social interaction with others has evolved into our society. Humans have not evolved to be solitary creatures. We require interactions with other people to remain healthy. Therefore, the relationships with people who are close to us, especially while young, can have a big impact on our health.

A Selective Look at Beards

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.”

Fat in Europeans Related to that of Neandertals

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.