Presentation Information
[O01-01]The Science of “Eating” Revealed by Isotopes: From Food Webs to Human Evolution★Invited Papers
*Naohiko Ohkouchi1 (1.Japan Agency for Marine-Earth Science and Technology)
Keywords:
Isotopes,Food web,Diet reconstruction
A portion of the solar energy reaching Earth’s surface is converted into biological energy through photosynthesis. Starting from plants, this energy is transferred to herbivores and then to carnivores through the act of “eating.” In this way, living organisms are interconnected through the flow of energy and matter, and their activities shape the surface environment of our planet. But how can we determine what organisms eat and how they are connected within ecosystems? In this lecture, I focus on isotopes—atoms of the same element with slightly different masses—and introduce methods for quantitatively analyzing food-web structures using nitrogen isotope ratios (15N/14N). Nitrogen isotope ratios serve as indicators of trophic level (an organism’s position in the food chain, from plants to higher-level consumers), and I will explain their basic principles and applications. These approaches allow us to investigate food-web structures in marine and lake ecosystems, assess the impacts of eutrophication on fish feeding habits, estimate fish migration routes, and even reconstruct the diets of modern and ancient humans. In fact, each of our bodies carries an “atomic record” of what we have eaten. Differences in diet are closely linked not only to ecosystem structure but also to human evolution. Variations at the atomic level can reveal how organisms live and how their histories have unfolded. Through the familiar act of eating, this lecture will explore the scientific fascination of connecting organisms, environments, and human society.