Science and Socioeconomics: Humans to Hyenas

Generally speaking, cellular biologists tend to ask questions about the ways small (likely microscopic) changes affect the end result of how organisms grow, survive, and adapt; how the “invisible” functions affect the visible. This is important for deepening knowledge of molecular biology, but can also seem pretty abstract or far removed from our daily lives. From a more personal (less science-obsessed) point of view, we may be more interested in the way daily life may be affecting our biology; how the "visible" can alter the "invisible" pieces and processes we are made of.  We all recognize that making the choice to smoke a cigarette can damage your lungs and too much alcohol can damage your liver, but what if something as seemingly passive as your social status could affect the most fundamental building blocks of your biology? 

Let's Start Small.

Blueprint.jpg
Top Image from City-Data.com, Bottom Image from Blick Art Materials

Top Image from City-Data.com, Bottom Image from Blick Art Materials

DNA is what differentiates a rabbit from a rhino. It serves as the coded instructions for what an individual cell becomes, as well as regulating the functions that individual cell will have. Something this important wouldn’t be kept unprotected, so it is compacted nicely into a shape we recognize as chromosomes and kept behind walls of molecules. If DNA is the blueprint, you can think of chromosomes as the cardboard tube it gets safely rolled up into for protection. That protective tube has plastic caps on both ends to prevent the important information inside from becoming frayed, crinkled, or torn. Similarly, DNA has structures called telomeres.

Location of telomeres on the ends of eukaryotic DNA. Image from HudsonAlpha Institute of Biotechnology. 

Location of telomeres on the ends of eukaryotic DNA. Image from HudsonAlpha Institute of Biotechnology. 

A telomere is a really long repeating part of DNA, located at both ends of the DNA strand. Existing in most eukaryotes, telomeres don’t have code to create proteins or other mechanisms but instead serve as a preventative measure against damage to the very precious genes. Nature isn’t perfect and DNA replication is no exception.

 

Whenever DNA needs to be copied in order for a cell to divide and duplicate itself, an enzyme called DNA Polymerase attaches to the DNA, follows along the linear sequence like a train on tracks, and copies all the important genetic information. DNA Polymerase must detach and stop copying information before it runs off the end of the strand and so each successive new copy made becomes just a little bit shorter as a little bit of the DNA is left out.  This might seem like a worrisome situation, but no crucial genetic information is lost because only snippets of the telomeres are neglected! This molecular mechanism ensures that all essential coding information gets copied each time a cell needs to make a new copy of itself. No problem-o. Well, for most of our lives anyway.

Aging isn't just about adding on years to your lifespan. It is itself a complex set of physiological processes generally associated with hindrances on functions of cells and tissues. It’s well established that the length of human telomeres in dividing cells of the body decreases as age increases. Once telomeres are shortened dramatically, or lost completely, signals within that cell tell it not to copy and divide anymore. This means that parts of us that used to be able to replenish and repair by the growth of new cells will slowly lose the ability to do so.

Telomeres and their degradation over time. Image from Reflexions, University of Liège.

Telomeres and their degradation over time. Image from Reflexions, University of Liège.

The Bigger Picture.

As you'd imagine, variation between the ways different individuals age is vast and largely reflective of the individual life history; physical activity, diet, sickness, environmental challenges…basically, the stuff that makes up your day-to-day life. Epidemiological studies, which look at the incidence and patterns of disease and health trends across human populations, have been able to connect the fields of socio-economics and biology. Low socio-economic status is correlated with a higher probability of physical and psychiatric disease, infant mortality, and shortened overall lifespans versus people who have access to more, and higher quality, resources. 

What Telomeres Tell.

People who are ranked as having low socio-economic status are reported to have shorter telomeres than peers within the population who have high social status. Even by examining individual aspects of our social being, such as employment status and education background, a difference in telomere length can be observed between individual people where those employed and more highly educated have longer telomeres. Additionally, it’s suggested that long-term exposure to poor environmental conditions and stressors (both psychological and physical demands) perhaps have the strongest influence on telomere length, driving their degradation and becoming especially apparent in older age. As more scientists keep exploring questions related to social hierarchy and affects on cell biology, longitudinal data can be collected and analyzed to understand what’s happening over time as an individual, its environment, and its class may shift and change.

Spotted hyena in Kenya. Image by Frans Lanting, National Geographic.

Spotted hyena in Kenya. Image by Frans Lanting, National Geographic.

Welfare to Wildlife.

Humans aren’t unique in the fact that we function within a structured social system. Hyenas can’t read Hemingway, but they do live in organized clans of high-ranking and low-ranking animals. Those members who are high up in the social ladder have easier access to more resources (such as space, food, and mates) and force the lower class individuals to travel distances to enter stressful new territories in search of resources. Earlier this year a brief paper was published showing, for the first time in a wild mammalian species, that long telomere length is correlated with high social standing in spotted hyena (Crocuta crocuta) groups. Five separate populations were examined, and despite variations in resource accessibility and environment between the locations of these groups, the correlation of status and telomere length held true; a result not skewed by age because telomere length is not a reflection of age in the spotted hyena. It’s suggested that perhaps this result was seen as a result of the higher costs of living in low-ranking members of the clan, compounded by higher levels of circulating stress-related hormones.  

 

Cartoon from The New Yorker. Kanin. 

Cartoon from The New Yorker. Kanin. 

This is a striking reminder from the animal kingdom that social class is a determinant of more than what one can toss into their grocery cart. In a capitalist world our species is divided largely according to financial status, but this has a large affect on access to a variety of other resources in our social, commercial, and natural environment. We are animals, and we struggle just like other social species to succeed in a harshly competitive world; one which cuts down to the very making of us.

As politics and biology collide, can we control the way that world affects us?

 

"All animals are equal, but some animals are more equal than others." - George Orwell