Tejada et al., 2015. Life in proto‐Amazonia: Middle Miocene mammals from the Fitzcarrald Arch (Peruvian Amazonia)
Terrestrial vertebrates of the Pebas megawetland system, middle Miocene of Peruvian Amazonia. Depicted in the image (clockwise from bottom left): glyptodont Boreostemma, astrapothere Granastrapotherium snorkii , ground sloth Pseudoprepoterium, rodents Neoepiblema, Toxodon Pericotoxodon, and terrestrial crocodile Sebecus huilensis.

Isotopically speaking we are what we eat because the elements that we use to synthesize our tissues (e.g., carbon or nitrogen) come primarily from food we eat and the waters we drink. Consequently, dietary isotopic signals get recorded in organismal tissues.

Five million years ago, in the Pliocene, the South American Andean mountains were inhabited by megamammals with no close relatives or ecological equivalents in the present, such as giant ground sloths, glyptodonts -heavily armored armadillos- and a variety of native hoofed herbivores. These animals resulted from a 60-million-year evolutionary process that occurred when South America was an island continent. This reconstruction depicts a new rich Pliocene fossiliferous site in Espinar (Cusco Department), in the Peruvian Andean Plateau (~3900 of altitude). The fossil mammals discovered include (clockwise from bottom left corner): a medium-sized glyptodontine new to science, Andinoglyptodon mollohuancai, three species of large ground sloths (up to 1800 kg), and one rhino-like ungulate (center of image). These fossils from the Peruvian Andes reveal details of life in the Pliocene, just before the arrival of the immigrant mammals that characterize South American ecosystems today. Reference: Salas-Gismondi et al., 2023. Pliocene Pre-GABI herbivorous mammals from Espinar, Peruvian Andean Plateau. Journal of Vertebrate Paleontology, e2237079.

When it comes to survival of the fittest, change is the only constant
In 1973 the evolutionary biologist Leigh Van Valen quoted Lewis Carroll’s Red Queen as a metaphor to explain what he viewed as the main driver of the diversification and extinction of species: the struggle of life itself. The Red Queen hypothesis argues that species must constantly adapt—or “run” in the queen’s words—as a survival mechanism. The constant competition for resources is what keeps us running. When one species becomes better at acquiring resources, the other species must adapt to keep up—“to keep in the same place.” This cancels out the long-term advantage of the adaptation in a single species. The Red Queen hypothesis relies on the understanding that biotic interactions underlie the evolution and extinction of species. Although Red Queen dynamics seem to be mostly limited to short timescales (less than one hundred thousand years), there are examples attesting to the role of biotic forces as an evolutionary driver over long timescales.
While in the Red Queen hypothesis, intrinsic traits pertaining to or originating from inside an organism or cell are the major drivers of biodiversity, in the Court Jester theory, extrinsic abiotic factors—things related to the physical environment, like climate change, tectonics, or extraterrestrial impacts—play a more important role in shaping the diversity of life. Court Jester hypotheses imply that shifts in the physical environment can change the rules imposed by biotic interactions. Thus an important difference between the Red Queen and Court Jester models of evolution is the timescale in which they seem to happen. Court Jester processes are known to prevail at longer timescales than the Red Queen dynamic, at over one hundred thousand years...
Extract of article by Julia Tejada for the Spiral Magazine, Rubin Museum of Art (Impermanence issue)
Complete article at https://rubinmuseum.org/spiral/a-royal-duel-in-the-natural-world/

Artistic reconstruction of Pebanista yacuruna, a new species of river dolphin from the Miocene (~15 Myr) of proto-Amazonia. Pebanista was found in an expedition carried out in 2018 along the Napo River, in Peru, and represents the largest known river dolphin, with an estimated length of 3 meters (almost 10 feet). Pebanista is the closest known relative of the extant South-Asian river dolphin Platanista and attests to the later independent colonization of South American freshwater environments by the extant South Amercan river dolphin Inia. Reference: Benites-Palomino et al. 2024. The largest freshwater odontocete: A South Asian river dolphin relative from the proto-Amazonia. Science Advances 10, eadk6320.