Manual dexterity of 44 wild gorillas of all ages and both sexes was investigated on six naturally acquired feeding tasks of varied logical structure, which included multi-stage and bimanually coordinated procedures. At least 400 min observation of feeding per animal, and analysis at the level of bouts rather than individual actions, can be expected to produce statistically robust results; 22 years background data allowed effects of genealogy and injury to be investigated. Five tasks elicited very strong hand preferences in most animals (weakest on the simplest task), while one was usually performed with a strategy in which left and right hands were used symmetrically; the preferences were fully established at 3 years old. Preferences were highly correlated within each of two sets of tasks, but between the two sets there was no correlation across animals in direction or strength of preference. No population trends towards left or right handers were found in either set of tasks, or both sets pooled; distributions were U-shaped and approximately symmetric, with a slight bias towards right-handed fine manipulation in one set of tasks. Processing efficiency was only slightly greater with the preferred hand, and similar in left- and right-handed animals. Neither direction nor strength of hand preference showed a tendency to run in families, but females showed greater strength of preference. Major injury masked strong hand preference, but injuries could not account for the overall distribution of preference; instead this may reflect inbreeding. Feedback acting on initially random hand choices, and imitation at the "program" level rather than slavish copying of acts, are proposed to account for the results.

The skills that mountain gorillas use to deal with the stings, tiny hooks, and spines protecting common plant leaves in their diet were examined for variation within and between animals. Many elements of uni-and bimanual performance were identified, often involving delicate precision and coordination, and varying idiosyncratically, each individual having a different set of preferred elements. Many of these elements are functionally equivalent, and all but one weaned animals showed full processing capability; the history of the one exception suggests that early experience with the task may be important. Gorillas' idiosyncrasy in manual skill elements is entirely consistent with trial-and-error learning a t this level. By contrast, each individual uses very few techniques (structured sequences of elements) for most processing, and these techniques are the same across the population. Where animals deviate from this generalization, they largely employ the simpler technique normally used for undefended leaves. Lateralization increases from start to finish, consistent with a logical structure in which each stage has a laterality bias and each stage is sequentially dependent on the last. Variations from their commonest techniques occur in all animals (on average, about nine variant techniques were recorded from each animal). The repertoire of techniques increases significantly with age, whereas the repertoire of elements does not. This points to an initial reliance on a single logical structuring that is well established by weaning (about 3.5 years), with subsequent development of the ability to vary the technique used so as to take advantage of variations in the environment. Standardization of logical organization, despite variability between different animals in individual elements and behavioral laterality, suggests that the logical ordering of elements and the interrelationships of processing stages is copied by program-level imitation.0 1993 Wiley-Liss, Inc.

The manipulative actions of mountain gorillas Gorilla g. beringei were examined in the context of foraging on hard-to-process plant foods in the field, in particular those used in tackling thistle Carduus nyassanus. A repertoire of 72 functionally distinct manipulative actions was recorded. Many of these actions were used in several variants of grip, finger(s) and movement path, both by different individuals and by the same individual at different times. The repertoire appears somewhat greater than that observed in comparable studies of monkeys, but a far more striking difference is found in the use of differentiated actions in concert. Mountain gorillas routinely and frequently deal with problems that involve: (1) bimanual role differentiation, with the two hands taking different roles but synchronized in time and space, and (2) digit role differentiation, with independent control of parts of the same hand used for separate purposes at the same time. The independent control that allows these abilities, so crucial to human manual constructional ability, is apparently general in African great apes. Role differentiation, between and within the hand, is evidently a primitive characteristic in the human arsenal of skills.

In the Mahale Mountains National Park of Tanzania, a group of about 33 chimpanzees were observed to surround a leopard den containing a mother and at least one cub and to drag out and kill the cub. This is the first report of chimpanzees or any other primate species killing their potential predator’s offspring. The incident suggests that chimpanzees, without any weapons, can manage to defend themselves against a carnivore of at least up to leopard size, and implicates how the early hominids may have reacted against their potential predators.

Human 6-phosphofructokinase (EC 2.7.1.11) exists in tetrameric isoenzymic forms composed of muscle (M), liver (L) and platelet (P) subunits, which are under separate genetic control. In the adult, the proportion of these subunits in different organs reflects the relative activity of glycolysis versus gluconeogenesis. To elucidate the developmental basis for the observed distribution, we investigated the isoenzymic transitions of phosphofructokinase in human foetuses (12-40 weeks' gestation) by using high-resolution chromatography and monoclonal antibodies. We studied skeletal muscle, heart, liver and brain because these organs show very different glycolytic fluxes and isoenzymic patterns in adult individuals. Our results demonstrate that there is no unique 'foetal' form of phosphofructokinase in humans, but all three loci are variably expressed in all foetal organs during early gestation. As development proceeds, muscle and liver isoenzyme patterns show dramatic changes, with disappearance of P and L subunits in muscle and transient reappearance of M and P subunits in liver; in contrast, phosphofructokinase isoenzymes change little in brain and heart. Most changes occur at mid-gestation and near term, and adult isoenzyme patterns are expressed at birth, indicating that organ differentiation is complete. These studies show that phosphofructokinase undergoes changes of isoenzyme patterns similar to, but not identical with, those of other multilocus isoenzyme systems of glycolysis. The observed changes probably reflect changing patterns of gene expression, with repression of some loci and activation of others.