To explore diets in the past we focused on the analysis of dental calculus, or mineralized plaque. As it forms in the mouth over the lifetime of the individual, dental calculus traps markers of diet and behavior, including starch grains, proteins, lipids and DNA. It has proven to be a vital resource of dietary information, but it wasn’t clear how best to use this rare and limited archaeological material. Our early analysis proved it wasn’t possible to combine all the various analyses (e.g. starches and proteins and DNA) into one single “pipeline”. We therefore developed a lab-grown dental calculus that allowed us to test the effects of burial, changes in pH and other factors on the survival of starch grains. This new experimental system can provide other researchers a means to test the incorporation of various residues, and to see what methods are best adapted to extracting that information. Insights from these experiments allowed us to more carefully explore archaeological dental calculus samples, resulting in several high profile articles about, among others, the diets of the eastern-most Neanderthals.
To better understand the relative costs and benefits of consuming plant foods, we have pursued three areas of study: 1) Assessing variation in intrinsic nutritional properties to allow better predictions of past food choices, 2) exploring the factors that help determine food choices among a present-day hunter-gatherer group, and 3) accounting for the costs of cooking foods.
Many studies exploring the foods that our ancestors would have eaten in the deep past rely on previously published commercial literature, or on estimations for entire categories of foods based on single items. However, wild plants vary significantly between individuals, among habitats, seasonally, and from year to year in terms of their availability and nutritional properties. We have therefore collected better data on the nutritional and antifeedant properties of plants in several African environments that are similar to those used by our earliest ancestors. In contrast to expectations from previous studies, our results suggest that grasses were likely far more valuable, while plants growing in or near water were less nutritionally rich.
It often assumed in studies of human evolution that foragers choose the food that provides the greatest caloric benefit at the lowest cost. However, many other factors such as preferences and accessibility of food may also play a role. We have studied food decisions, energetics, and microbiome composition among the Baka forager/horticulturalists of Cameroon. During three field seasons, we collected a large variety of data using a novel combination of methods, including interview, observation, use of GPS and heart rate trackers. Our results suggest that this community considers both social influences and the energetic costs and benefits when choosing foods. Furthermore, gathering and agricultural work are the most energetically costly subsistence-related activities, but that the cost of gathering varies widely depending on the plant that is collected.
The benefits of fire for processing food have been well documented. However, the costs of fire have been largely ignored, despite the potential that they may have influenced when and how humans adopted fire use. We collected energetics data from three volunteers collecting firewood in three different habitats similar to those used by early European hominins. Fuel collecting in all three habitats was very energetically costly, and far outweighed the caloric benefit gained from cooking foods on those fires.
