Evidence of nonrandom positioning among adult males is crucial for a protection theory of the spatial organization of baboon progressions. In a recent study it was suggested that systematic positioning of troop members other than mothers and infants is so slight and rare that progressions may be regarded as essentially random. This suggestion depends upon debatable methodological points presumably downgrading previous findings of nonrandom order. Reanalysis of data from this study revealed numerous analytical and statistical problems, as well as serious calculation and other errors, and showed that the findings are consistent with results of the present and previous research. Adult males tended toward the front or back of progressions, a tendency which was intensified in potentially dangerous situations. Dominant males were disproportionately more often frontward and subordinate males rearward. Nonrandom order, which was found for a variety of circumstances at high levels of statistical significance, was unusually general in that it occurred in 6 studies, 7 troops, 2 species, and 5 locations. Such generality is consistent with a protection theory postulating phylogenetic underpinnings of a sociospatial organization which allows an advanced primate to adapt to terrestrial coexistence with predators.

Two feeding habits of 30 baboons selected equally from five age-sex classes were studied at Mikumi National Park, Tanzania. The finding, gathering, and preparing of sedge corms and of seeds of tamarind fruit were described in detail. Adults obtained these foods faster than younger animals, although even small juveniles and weaned infants were efficient in gathering and preparing them. While gathering sedges or tamarinds, adult males sat in one place longer than others and obtained more food per sitting. Adults ate more pieces of food per minute than juveniles, but adult rates of eating did not differ by sex. The adult rate of food intake was inconsistent with the assumption of different food requirements for males and females of a species with pronounced sexual dimorphism.

According to DeVore and Washburn's protection theory of the spatial organization of moving baboon troops, walking infants, which are among the most vulnerable and least self-sufficient of all troop members, should tend to occupy the troop's center. The protection theory is an ultimate hypothesis from which persistently recurring behavior is expected. Two troops living in Mikumi National Park, Tanzania, were compared with troops studied at other locations. Walking infants tended to occupy the center of their troop and to be underrepresented primarily in the frontal portion of progressions and secondarily in the rear. The lead position of progressions was analyzed using 82 walking infants, 11 troops, three locations, two species, and three studies involving eight or more observers employing somewhat different procedures at the different study sites.

Development toward independence during the early years of baboon life is reflected in the infant's transition from riding on its mother to walking on its own during progressions from one location to another. This transition was studied during the first year of life in 55 infants from two differently sized troops living in Mikumi National Park, Tanzania. There was a nearly linear transition in the first year from almost 100% ventral riding to almost 100%walking. The amount of dorsal riding started near zero, reached a plateau lasting from about the 15th to the 26th wk of life, and then gradually declined to zero. Dorsal riding did not replace ventral; rather, dorsal riding increased in frequency until it occurred about as often as ventral riding. Prolonged ventral riding by infants of the smaller of the two troops may have been due to spacing differences or to greater nervousness among members of the smaller troop. There were no significant differences in riding or walking associated with the time of day or the infant's sex. The rate of transition from riding to walking was greatest from about the fifth to the seventh months, which may be especially significant time in the early development of independence.

Age-sex differences in the sociospatial positioning of progressing baboon troops have been postulated as an important, protective aspect of baboon adaptation to a terrestrial existence. The protection theory is an ultimate hypothesis which can be disproven by showing that the postulated age-sex positioning fails to occur. Alternatively, confidence in the protection theory can be increased if the postulated positioning persists across several troops despite significant opportunities for variation, and if progression order is shown to be linked to biological phenomena such as sex differences in physical maturation. Data from 73 individually identified, free-ranging juveniles of both sexes were compared with previous findings. Small juveniles of several troops were more centrally located than large juveniles. Large juveniles males were more toward the front than were large juvenile females. As male walking infants and juveniles aged, a change in positioning (i.e., location) occurred: males were located increasingly toward the front of progressions. Comparable data from females suggest that the adult female pattern had begun to form among large juveniles. Data are consistent with an ultimate protection theory.An early form of a protection theory of sociospatial organization of moving troops was proposed by DeVore and Washburn (1963) to explain in part baboon adaptation to a terrestrial existence among predators. The central tenet of the protection theory is that progression order of moving troops should take a nonrandom form in which vulnerable animals are less exposed to danger than more selfsufficient troop members. DeVore and Washburn proposed an order in which dominant adult males, infants, and small juveniles were central, and subordinate adult males were peripheral. In a modified version of the theory (Rhine, 1975;Rhine and Westlund, 1981), to which the present paper is addressed, walking but not riding young are considered the most vulnerable animals, and any large males, dominant or otherwise, are expected under most conditions to occupy the exposed positions to the front or rear during progressions more often than are other animals.As an ultimate hypothesis, the protection theory will neither be proven in the laboratory nor fully tested by a single field study. Rather, like other hypotheses about the natural social behavior of highly intelligent animals, it can be repeatedly investigated under a variety of relevant free-ranging conditions. If accumulating data from such investigations tend to contradict the theory, then it must be either plausibly modified or discarded. As long as the data are reasonably consistent with the theory, it is likely to remain the prevailing explanation until a better alternative is proposed.The protection theory implies a significant phylogenetic basis of progression order; therefore, the postulated order should be