Describe in detail three anatomical features unique to humans that adapts them f
ID: 3481853 • Letter: D
Question
Describe in detail three anatomical features unique to humans that adapts them for endurance running. Describe the specific anatomical features and how is it thought to be an adaptation for endurance running compared to that of other primates. Endurance running and the evolution of Homo Dennis M. Bramble & Daniel E. Lieberman Deparsment of Biolegy, University of Utak Salr Lake City, Uah 84112 USA nabody Alunan, Harward Universit% Gambri ge, Massaduoto 02138, USA Striding bipedalism is a key derived behaviour of hominids that possibly originated soon after the divergence of the chimpanzee and human lineages. Although bipedal gaits include walking and running, running is generally considered to have played no major role in human evolution because humans, like apes, are poor sprinters compared to most quadrupeds. Here we assess how well humans perform at sustained long-distance running, and review the physiological and anatomical bases of endurance running capabilities in humans and other mammals. Judged by several criteria, humans perform remarkably well at endurance running thanks to a diverse array of features, many of which leave traces in the skeleton.The fossil evidence of these features suggests that endurance running is a derived capability of the genus Homo, originating about 2 million years ago, and may have been instrumental in the evolution of the human body form. h endurance running ost research on the evolution of human locomotion How well do humans run long distances? has focused on walking. There are a few indications In considering human running, it helps to start from the perspective that the earliest-known hominids were bipeds of the basic biomechanical differences that distinguish running and and there is abundant fossil evidence that australo walking gaits in all mammals, including human bipeds. Thee pithecines habitually walked by at least 4.4 milion dafferences are well characterized. Walking uses an inverted pen years (Myr) ago Mamy researchers interpret the evolution of an dulam in which the centre of mass vaults over a relatively extended essentially modern human-like body shape, first apparent in carly leg during the stance phase, efficiently exchanging potentiall and Homo erectus, as evidence for improwed walking performance in kinctic energy out-of phase with every step (Fig la, b). The meta more open habitats that came at the expense of retained adaptations boic cost of transport (COT) for humam walking, le that of otho in the australopithecine postcranium for arboreal locomotion (formak, is a U-shaped curve, in which optimal speed, approxi mately 1.3ms ,is largely a function of leg length Most bumans example, refs 58). Although the biomechanics of running, the other human gait, is well studied, only a few researchers (see refs 9, 10 for example) have considered whether running was a mode of locomotion that in uenced human evolution. This lack of attention is largely because humans are mediocre runners in several respects Even elite human sprinters are comparatively slow, capable of very diffierently (Fig. 1b). Collagen-rich tendons and ligaments sustaining maximum speeds of only 10.2ms or less than 15t store clastic strain In contrast, mammalian cursorial specialists such as horses grey thc voluntarily switch to running at approximatcly 23-25ms which corresponds closely to the intersection of the COT curves for walking and running in humans (Fig. 2bAt those higher spends running becomes less costly than walking by exploiting a mass-speing mechanism that exchanges kinetic and potential energy support phase, and then release the emergy through recoil during hounds and pronghorn antelopes can maintain maximum gallop the subsequent propulsive phase.To use these springs effectively ing speeds of 15-20ms for several minutes". Moreover, running the legs flex more in running than in walling fleing and them is more costly for humans than for most mammals, demanding extending at the knee and ankle during the support phase (Fig la) roughly twice as much metabolic energy per distance travelled than Limb stiftness relative to body mass in running humans is similar to Finally, human that of other mammalian cursors is typical for a mammal of equal body mass runners are less manoeuvrable and lack many structural modifi- cations characteristic of most quadrupedall cursors such as elongate digitigrade feet and short peoximal limb segments. Although extensive data on endurance capabilities are not avail able for most quadrupedal mammalls, several lines of evidence indicate that humans, using criteria such as speed and sustainable However, although humans are comparatively poor sprinters, distance, are much better endurance runners than has generally been appreciated. Human ER speeds range from approximately 23 they also engage in a different type of running.endurance running (ER), defined as running many kilometres over extended time to as much as 6.5ms periods using acrobic metabolism Although not extensively studied in elise athletes Average ER speods for (ref.21). Froma ocreational joggers range j between 3.2-4.2ms evolutionary perspective, it is important to note that human ER exceptional compared to non-human primaties. Apes such as chimpannees, and other primates, such as patas monkeys can sprint rapidly, but they do so rarely and only for short in non-humans, ER is unique to humans among primates, and uncommon among quadrupedal mammals other than social carni- vores (such as dogs and hyenas) and migratory ungulates (such as wildebeest and horses), Here, we review the evidence for and impact of ER in human evolution. We begin with a discussion of the mechanical differences between walking and running, and how well humans perform at ER compared to other mammals. We then review what is known about the key structural specializations thought to underlie human ER capabilities, the extent to which they may be features that evolved originally for bipedal walking,and the evidence for their appearance in distances"" No primates other tham homans arne capable of ER Quadrupedal cunsors casily sprint faster than humans over short distances, but sustainable ER speeds of humans are surprisingly comparable to specialized mammalian cursors such as dogs and horses in two respects. The first comparison to trotting, because bipeds are incapable of galloping, but also because human bipedall running and quadrupodal trotting are biomechani- the hominid fossil record. We cally most comparable. Both gaits synchronize contralateral fore- conclude boutlining some hypotheses for hy ER capabilities and hindlimbs, effecti ely reina gaáadesetspt he initially arose in the genus Home and the significance of this steps, and both are inherently bouncy gaits with substantial behaviour for human evolution. vertical displacements of the centre of mass.When compared NATURE I VOL 432 28 NOVEMBER 20al www.ut.ac.iallaanv 2004 Nature Publishing GroupExplanation / Answer
answer: the three antomical features are
specific anatomical features are