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22 “I Know Who You Are; I Know Where You Live” Judith Masters If we can reasonably speculate that consciousness as we experience it in ourselves is at least partially, if not entirely, the emergent result of the aggregate feelings and interactions of post-bacterial cells, it behooves us to turn our attention to the “mental capacities” of groups of animals— behaving, solving problems, and setting and accomplishing goals as collectives. Here Masters follows jungle primates that keep track of one another in dispersed social networks. Living primates are classified into two suborders: the Haplorhini (literally , simple nostrils), which includes tarsiers, monkeys, and apes, and the Strepsirhini (twisted nostrils), which includes the lemurs of Madagascar (see chapter 15) and the lorises and galagos of Africa and Asia. All haplorhine primates, with the exception of Southeast Asian tarsiers and South American owl monkeys, are diurnal and gregarious. They have well-developed visual systems with binocular (stereoscopic) vision and notable visual acuity. The foveas in their retinas have a high percentage of cones (modified cilia, see chapter 13), which allow color discrimination . All African and Asian monkeys and some New World monkeys have trichromatic vision: they have three kinds of photopigments with peak wavelength sensitivities in the blue, green, and red regions of the color spectrum (see chapter 11). Thus, their communication repertoires often include striking visual signals. For example, the callitrichines of South America and the cercopithecoids of Africa and Asia use strongly contrasted color patterns to signal their species identity. Our own diurnal habits and visual sensitivities generate instant color skin recognition and pelage (fur) differences. They are signals of taxonomical significance. Some of the lemurs on the island of Madagascar (e.g., Varecia variegata, Hapalemur aureus, Eulemur coronatus, and members of the 252 Chapter 22 E. fulvus species group; see chapter 15) have incorporated color into their signaling systems, and this too correlates with diurnal activity. Although most of the larger lemurs have been described as diurnal, closer study has shown that many are active both by day and by night, an activity pattern we call cathemeral (Tattersall 2006; chapter 15 above). These lemurs may lack a typical tapetum or any tapetum at all (e.g., those in the genera Varecia and Eulemur). Lemur catta and Hapalemur griseus have rudimentary foveas with both cone and rod receptor cells (Pariente 1975). The cones are much sparser than in haplorhine primate retinas, and color discrimination in lemurs ranges from exceedingly poor to fair. The quality of the sensitivity and the response to color depend on light intensity. Trichromatic vision may exist in Propithecus and Varecia (both diurnal) and in the nocturnal Cheirogaleus. The majority of lemurs, however, like their relatives on mainland Africa and Asia, are active only at night. In a dense forest, the canopy filters 99 percent of ambient light (Charles-Dominique 1977). The visual systems of nocturnal strepsirhines have evolved to detect this paucity of light by hypertrophy of the eyeball and the development of a reflective tapetum behind the retina that amplifies whatever incident light impinges on the retinal rod cells. The absence of a fovea and the virtual absence of cones do not preclude the use of vision in the perception of the nocturnal environment of these primates. They move around in relative darkness, some by rapid, almost ricochetal locomotion; they leap from one vertical support to another with great accuracy. However, the primary senses used in nocturnal foraging are olfaction (chemosensory) and hearing (mechanosensory) via kinocilia and stereocilia of the inner ear and balance organ (see chapter 13). They are crucial, too, for intraspeci fic communication. Body odor is extremely important to the strepsirhine way of life, and strepsirhines are distinguished from the haplorhine primates by the development of two adaptive features used in the grooming and maintenance of the fur. Living strepsirhines (with the exception of Daubentonia, the aye-aye) share a modification of their lower anterior dentition: the toothcomb . The long, attenuated canines and incisors are rotated horizontally. The absence of functional canines has led to the evolution of caniniform anterior premolars. Under the tongue is a cartilaginous sublingua with fringed edges or lappets that are inserted between the tines of the comb to dislodge detritus that collects there. Additionally, the nail of the second toe is modified as a grooming claw, used to remove debris from the fur. By grooming themselves and their neighbors, strepsirhine [3.145.23.123] Project MUSE (2024-04-19 01...

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