15 Feb 2019

We have become less dense: Osteoporosis Prevalence from Past to Present

Liz Ronald '19

Osteoporosis is a worldwide disease that affects millions of people. The present statistics of osteoporosis are enormous compared to the prevalence of the disease in the past. Most of the archaeological record contains individuals with low bone density but not the diagnosis of osteoporosis, which can lead to life-threatening fractures. The Industrial Revolution marks an important turning point in which osteoporosis begins to become more prevalent. Reasons for this change include nutritional stressors, physical activity inefficiencies, and other socio-cultural tendencies that influence the probability of an individual developing the disease based off of genetic characteristics the individual may already have. Other factors that are associated with an increased prevalence of osteoporosis in the present population include longer life expectancies as well as pregnancy and lactation stress that occur when women are able to have more children. Aspects of people's lives changed due to the transition from hunter gatherer and paleolithic lifestyles of food production and high activity levels to agriculturalist lifestyles of sedentary living and mass food production which is fundamental in the prevalence of osteoporosis. These changes, instigated by the Industrial Revolution, most likely caused the cultural and societal shifts that led the disease of osteoporosis to physically portray more often in the present than in the past displayed in the archaeological record.

Correlation between Aggression and Persistence in Eastern Grey Squirrels (Sciurus carolinensis)

Sydney Elwood '19

Many animal species exhibit behavior variants at an individual level that differs from their other conspecifics, such as in boldness, exploratory nature, risk-taking, persistence, and aggression. The accepted definition of personality in the animal kingdom is when an individual behaves in a consistent, repeated way that is different from other individuals. The possibility of a correlation between two personality traits, such as boldness and aggression, is a less explored area. Personality has been observed in many species, from mollusks to mammals to birds, but it has not been thoroughly studied in eastern grey squirrels (Sciurus carolinensis). Via informal observations at the Wildlife Rehabilitation Center of Minnesota, individual squirrels have exhibited unique behavioral variations in aggression, boldness, and persistence. In this field study, the possible correlation between persistence and aggression in wild eastern grey squirrels was investigated. The aggressive trait was hypothesized to be correlated with high persistence and the non-aggressive trait with low persistence. In Minnehaha Park of Minneapolis, Minnesota, seven wild squirrels’ personalities were observed. Aggression levels were tested by observing an individual's behavior and reaction to a perceived conspecific by placing a mirror under a baited tree. An individual’s persistence levels were assessed by the time spent obtaining food from a challenging container or an easier opened container of food, which was placed under another baited tree with a mirror as a control. The aggression levels unique to each individual’s personality could not be accurately measured in this study, but the squirrels exhibited a correlation to persistence and risk assessment. Squirrels perceived the mirror conspecific as a risk when food was present, and the amount of time spent obtaining hard to access food varied between each individual. Future research is necessary to establish if a correlation between low persistence and low-risk taking and high persistence and high-risk taking behavior. This is a promising new area of research in the personality of mammals.