The evolution of plant–animal interactions goes back to the Early Archean, when the first signals of photosynthesis may have been detected in the Isua Peninsula in Greenland, a phenomenon that is related to the isotopic anomalies of carbon. The first evidence of reliable fossils of photosynthetic microorganisms has been identified by micropaleontologists in the Late Archean and Early Proterozoic. A closely related topic in this geologic time interval is the evolution of trophic relations and metabolic diversification in the microbial world. In the context of the three domains of life, Archea, Bacteria, and Eucarya, the bifurcation of multicellular organisms into plants and animals becomes evident only during the Paleozoic. Cell evolution also leads up to the unicellular dichotomy of autotrophs and heterotrophs. Symbiosis has a strong role to play in the transition to plants and animals in the Phanerozoic. It is timely to focus on the details of evolution in the Cretaceous and Tertiary, where detailed pathways of evolution have been gathered in many geographical regions, including the Karst region of northern Italy. Various experimental techniques have contributed to elucidate the coevolution of plants and animals. A special case of plant–animal interaction is the evolution and dispersal of hominins, including their impact on the ecosystems. A significant development in understanding the evolution of plant–animal interactions is based on the possibility of identifying reliable biomarkers that can characterize its different stages, from the earliest microbes to the extant plants and animals. Such identification of biomarkers labeling different stages of evolution may orient the search for life in the exploration of the Solar System.
