Evolution of hallucial grasping in the primates

The hands and feet of Archaeolemur: metrical affinities and their functional significance

“…The hallux of Archaeolemur is reduced and less prehensile; this is decidedly unlike all other living strepsirrhines and some subfossil species (e.g., Megaladapis has a massive, pincerlike hallux; Wunderlich et al, 1996). Szalay and Dagosto (1988) noted that the entocuneiform of Archaeolemur bears a reduced and mediolaterally compressed articular facet for the hallucal metatarsal (see also Lamberton, 1938). This implies a reduction in its range of abduction, but ''there is nothing in the joint, however, which would have prevented the hallux from performing grasping while climbing'' (Szalay and Dagosto, 1988: 17).…”

“…Because forces pass to the animal from the substrate and from the animal back to the substrate via the hands and feet, the anatomy and shape of these organs reflect locomotor and postural biomechanics more faithfully than perhaps any other parts of the musculoskeletal system (Jouffroy and Lessertisseur, 1979;Susman, 1979;Gebo and Dagosto, 1988;Szalay and Dagosto, 1988;Lewis, 1989;Lemelin, 1996;Wunderlich et al, 1996;Jungers et al, 2002). Opportunities to examine this informative formefunction relationship in the fossil record are rare but invaluable (Stern and Susman, 1983;Godinot and Beard, 1991;Gebo, 1993;Wunderlich et al, 1996).…”

“…The indices for our three specimens (mean Z 56.5%) fall below those of all taxa included in this study and below all mean values for the same index reported by Strasser (1994: table 1 therein). Compared to other living strepsirrhines and subfossil species such as Megaladapis , hallucal reduction in Archaeolemur is especially marked, suggesting reduced and/or different (i.e., non-strepsirrhine) grasping capabilities in this subfossil genus (Lamberton, 1938;Dagosto, 1986;Szalay and Dagosto, 1988). Megaladapis is considerably larger than Archaeolemur, so hallucal reduction in the latter is clearly not a size-required adaptation of all extinct giant lemurs.…”

“…To this end, we compare here the proportions of the various elements of the hands and feet of Archaeolemur to those of living Malagasy lemurs, Old World monkeys, and selected nonprimate mammals. The functional anatomy of the hands and feet is especially closely linked to posture and locomotion because these organs contact the structural environment directly and form the biomechanical link through which forces are transferred to the postcranium, an opinion we share with many others (e.g., Lessertisseur and Jouffroy, 1973;Etter, 1973;Jouffroy andLessertisseur, 1978, 1979;Gebo and Dagosto, 1988;Szalay and Dagosto, 1988;Latimer and Lovejoy, 1989;Lewis, 1989;Strasser, 1994;Hamrick, 1995Hamrick, , 1996aLemelin, 1996Lemelin, , 1999Wunderlich et al, 1996).…”

Primate origins, human origins, and the end of higher taxa

“…Textbooks of physical anthropology will tell you that there are three or four theories of primate origins: the old arboreal theory, which describes the euprimate traits (or trends) as the inevitable outcome of life in the trees; the similar ''grasp-leaping'' theory of F. S. Szalay, who sees the euprimate traits as having originated as adaptations to acrobatic leaping in trees; 39,40 my ''visual-predation'' theory; [35][36][37][38] and R. W. Sussman's thesis that the euprimate traits originated in connection with the exploitation of fruit and nectar. 41,42 But this narrative of conflicting theories falls apart on closer examination.…”