How humans and their closest kin perceive the world: The special senses of primates

I suppose that if I were a whale, or a ubiquitous and indefatigable New York cockroach, I would take umbrage to this issue of The Anatomical Record. Indeed, how anthropomorphic—or, more correctly, primatomorphic— could Linnaeus have been when, in 1758, he anointed humans and our closet kin the “Primates” or “Firsts” (Linnaeus, 1758). Paleontology has shown us that we were neither the first mammals to creep out of the Cretaceous nor the most numerous. Similarly, behavioral studies have shown that not all primate species are mammalian summa cum laude graduates, while the advanced communication skills and social complexities of some other mammals, such as cetaceans, put many of our tree-hugging brethren to shame. Nevertheless, we control the press; Moby Dick and Flipper don’t. Hence, we’re the Firsts. With that nod to the perennially jealous nonprimatologist, we can turn to our own ilk. First, scientists and the lay public alike are fascinated by other primates because we are fascinated with ourselves. For most of us, that beautiful face in the mirror every morning is the end product of natural selection. The myriad of anatomical, behavioral, and evolutionary questions on who we are, what is special about humans, and how we came to be cannot be appreciated without a detailed exploration of our closest relatives, the other primates (spelled with a capital P and pronounced “pri-MAY-tees” only when used as the proper noun). For the noncognoscenti, it should be admitted that it is not always clear who actually is a primate; both comparative biologists and paleoprimatologists have had a few good bouts over this question. Generally, however, we have reserved seats at the table for ourselves (and evolutionary parents, grandparents, and relatives, whoever they are), the great and lesser apes, monkeys (both Old World monkeys from Africa and Asia and New World monkeys from the Americas), and the prosimians. This latter group is comprised of an odd mix of tarsiers, Malagasy lemurs, lorises, galagos, tree shrews, and the like, who often seem far removed physically and behaviorally from us. Indeed, many of the scientific arguments over primate origins and systematics have revolved around the position of families such as the rodent-like tree shrews (the Tupaiidae) and their insectivore-like ancestors who may sit at crucial branching points in the emergence of our order [see classic reviews in Szalay and Delson (1979) and Martin (1990)]. Primates are undeniably diverse in their history, appearance, and capabilities. This special issue of The Anatomical Record on the “Evolution of the special senses in primates” presents state-of-the-art research and reviews on central aspects of howmembers of our extended family perceive and interact with the world. The issue has been guest-edited by Timothy Smith, Callum Ross, and Nathaniel Dominy, three functional morphologists who bring to the table not only breadth and depth in their areas of anatomical expertise, but a collective energy to place their, and their colleagues’, studies into an all-important evolutionary context. The focus of these articles—based on a recent symposium of the same name held at the 2004 annual meeting of the American Association of Physical Anthropologists in Tampa, Florida—is the traditionally held “special” senses, i.e., those for sight, hearing, smell, and taste. These senses have commonly been considered together as they employ specialized sensory receptors in the eye, ear, nose, and taste buds to transmit external stimuli via cranial nerves to brain centers wherein they are registered as sensations. While the issue centers on the evolution of the special senses, the larger topic of general somatosensory evolution is covered in some of the articles as well, thus putting the special senses in a broader functional and evolutionary context. This issue represents an excellent collection of anatomical, physiological, paleontological, and behavioral studies on the underpinnings of how our kind interacts with the world. It is an excellent example of how functional morphologists can use the material at hand from both living and fossil material to extract the path of how the special senses evolved and, indeed, what may be special about them in primates. Whether or not we and our hairy clan deserve to be the “Firsts,” the story of how our senses came to be is a crucial one in understanding our history. This special issue of The Anatomical Record will add considerably to that knowledge.