Evolutionary fitness is based on an organism’s ability to adapt rapidly to changing environmental circumstances. Large-bodied mammals have been equipped with large brains (and hence a high information storage and transfer capacity, Tehovnik and Chen 2015), so that they can readily adjust their behavior to change. Now that the planet is heating up because of CO2 emissions caused by that large-brained species, Homo sapiens (Hansen et al. 1981), it is up to them to adjust their behavior from an economic growth-to-bust model (which is the model used by ant colonies, Wilson 2012) to a sustainability model which is in keeping with the way the indigenous tribes of the Amazon, for example, have subsisted for millennia (Everett 2016). Most who are in love with the HBO series ‘Succession’ and who have been indoctrinated by Milton Friedman and the Austrian School of Economics consider ‘Sustainability’ a code word for ‘Communism’. But nature does not care what one calls it (see Jeffrey Sachs 2024 on sustainability/YouTube).
Here are some facts about fitness according to the evolutionary behaviorist, Barbara Finlay, summarized. The smallest and largest primates differ by a thousand-fold in body size. This translates from three to nine orders of magnitude in potential population growth rate: “A female mouse lemur (Microcebus murinus) born at the same time as a female gorilla (Gorillas gorilla) could leave 10 million descendants before the gorilla becomes sexually mature.” (Harvey, Finlay et al. 1989, p. 14) Nevertheless (despite the reduced fecundity), large animals typically have fewer predators thereby increasing the chances of survival; but on the other hand, an natural disaster that damages the food chain will be most devastating to large animals as happened to the dinosaurs 65 million years ago (Alverez et al. 1979). The longest a human can live without food and water is about one week, which means that being confronted with such a condition it is impossible for a newborn human to reach sexual maturity. In short, the larger the organism the more devastating a natural disaster (note the infant deaths in current-day Gaza). Animals with a short reproductive cycle have an advantage here, and it is this advantage that allowed small mammals to replace dinosaurs (and evolve into large-brain mammals), as the earth recovered from its fifth extinction.
Not all dinosaurs were big - birds are dinosaurs, and they survived. Also non-dinosaurian reptiles crocodiles, turtles . . . also many microorganisms had huge diversity losses. You might also ask why did small amphibians rise to dominance in the stead of mammals? It all depends on the environment and (pre)adaptations - its a numbers game: game theory.
Dear Leslie F. Noè:
Thank you for your informed comments.
Ed Tehovnik
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