Evolution Driven by Organismal Behavior by Rui Diogo

Author:Rui Diogo
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

In summary, the empirical examples reviewed in this chapter show that phylogenetic relationships are often a better predictor of morphology—particularly of more “internal” anatomical traits such as details about the specific attachments of muscles, number of musculoskeletal structures, and so on—than are behavioral and/or ecological traits. Because one of the main fields of my research is biological anthropology, I will further illustrate this point by referring to an subject that was briefly discussed in previous chapters and to which readers can easily relate, because it concerns human evolution : the behavioral choice made by our ancestors a few million years ago to walk bipedally. In a very simplified way, it can be said that when the environment in East Africa became drier, our ancestors could no longer find food, such as fruits, by moving from tree to tree as they had done in the dense tropical forests and as many other primates still do in other parts of Africa and in other continents. In the new savannah environment, they had to come down from the trees and move along the ground to find other trees with fruits available. In response to that environmental change, humans could have behaved in many different ways: among all animals that lived in that area at that time, including other primates, humans were the only ones that became “fully bipedal ” since then, after all. Apart from having the needed behavioral, physiological, and anatomical plasticity to be able to walk bipedally, organisms also need to make an active choice to do so. During the millions of years that have passed since that initial behavioral choice, we have occupied many different habitats, from northern icy regions near the poles to high mountains, from islands to deserts, and even regions with very dense tropical forests in which our closest relatives (the apes) continue to live. Still, due to our behavioral persistence, we continue to walk bipedally, even when we go into those dense forests to observe some of those apes and various other species of primates, despite the fact that it would probably be more “efficient”—at least for certain moments—to move in the trees in such dense forests. I can attest this myself because when I went to observe the locomotion and tool use of wild chimpanzees in Uganda’s Kidale forest, it was particularly difficult to follow these apes when they were moving on trees. Our bipedal walking was completely inefficient in such dense forests, and the only way we were able to follow these apes in a not completely unsuccessful way was due to the help of the local guides who were continuously cutting through the dense vegetation with machetes. That is, bipedalism is surely not the most optimal type of locomotion that an animal could undertake for every environment we inhabit within the context all of the possible theoretical biomechanical options available.

Therefore, if one were to study the correlations between, for example, the type of locomotion, the musculoskeletal morphology, the phylogeny, and the different habitats of humans (e.

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