Bipedalism Standing or moving on two appendages is one of the defining characteristics of being human.
Genetic data based on molecular clock estimates support a Late Miocene ancestry. Various Eurasian and African Miocene primates have been advocated as possible ancestors to the early hominins, which came on the scene during the Pliocene Epoch 5.
Though there is no consensus among experts, the primates suggested include Kenyapithecus, Griphopithecus, DryopithecusGraecopithecus OuranopithecusSamburupithecus, Sahelanthropus, and Orrorin. Kenyapithecus inhabited Kenya and Griphopithecus lived in central Europe and Turkey from about 16 to 14 mya.
Dryopithecus is best known from western and central Europe, where it lived from 13 to possibly 8 mya.
Graecopithecus lived in northern and southern Greece about 9 mya, at roughly the same time as Samburupithecus in northern Kenya. Sahelanthropus inhabited Chad between 7 and 6 million years ago. Orrorin was from central Kenya 6 mya. Among these, the most likely ancestor of great apes and humans may be either Kenyapithecus or Griphopithecus.
Among evolutionary models that stress the Eurasian species, some consider Graecopithecus to be ancestral only to the human lineage, containing AustralopithecusParanthropus, and Homowhereas others entertain the possibility that Graecopithecus is close to the great-ape ancestry of Pan chimpanzees and bonobos and Gorilla as well.
In the former model, Dryopithecus is ancestral to Pan and Gorilla. On the other hand, others would have Dryopithecus ancestral to Pan and Australopithecus on the way to Homo, with Graecopithecus ancestral to Gorilla.
This morphology-based model mirrors results of some molecular studies, which show chimpanzees, bonobos, and humans to be more closely related to one another than any of Bipedalism the path to the future is to gorillas; orangutans are more distantly related.
In a phylogenetic model that emphasizes African Miocene species, Samburupithecus is ancestral to Australopithecus, Paranthropus, and Orrorin, and Orrorin begets Australopithecus afarensis, which is ancestral to Homo. The Miocene Epoch was characterized by major global climatic changes that led to more seasonal conditions with increasingly colder winters north of the Equator.
By the Late Miocene, in many regions inhabited by apelike primates, evergreen broad-leaved forests were replaced by open woodlands, shrublands, grasslands, and mosaic habitats, sometimes with denser-canopied forests bordering lakes, rivers, and streams. Such diverse environments stimulated novel adaptations involving locomotion in many types of animals, including primates.
In addition, there were a larger variety and greater numbers of antelope, pigs, monkeys, giraffes, elephants, and other animals for adventurous hominins to scavenge and perhaps kill. But large cats, dogs, and hyenas also flourished in the new environments; they not only would provide meat for scavenging hominins but also would compete with and probably prey upon them.
In any case, our ancestors were not strictly or even heavily carnivorous. Instead, a diet that relied on tough, abrasive vegetation, including seeds, stems, nuts, fruits, leaves, and tubers, is suggested by primate remains bearing large premolar and molar teeth with thick enamel.
Behaviour and morphology associated with locomotion also responded to the shift from arboreal to terrestrial life. The development of bipedalism enabled hominins to establish new niche s in forests, closed woodlands, open woodlands, and even more open areas over a span of at least 4.
Indeed, obligate terrestrial bipedalism that is, the ability and necessity of walking only on the lower limbs is the defining trait required for classification in the human tribe, Hominini. Striding through the Pliocene The anatomy of bipedalism Bipedalism is not unique to humans, though our particular form of it is.
Whereas most other mammalian bipeds hop or waddle, we stride. Homo sapiens is the only mammal that is adapted exclusively to bipedal striding. Unlike most other mammalian orders, the primates have hind- limb -dominated locomotion.
Accordingly, human bipedalism is a natural development from the basic arboreal primate body plan, in which the hind limbs are used to move about and sitting upright is common during feeding and rest.
Skeletal and muscular structures of a human leg left and a gorilla leg right. The initial changes toward an upright posture were probably related more to standing, reaching, and squatting than to extended periods of walking and running. Human beings stand with fully extended hip and knee joints, such that the thighbones are aligned with their respective leg bones to form continuous vertical columns.
To walk, one simply tilts forward slightly and then keeps up with the displaced centre of mass, which is located within the pelvis. The large muscle masses of the human lower limbs power our locomotion and enable a person to rise from squatting and sitting postures.
Body mass is transferred through the pelvis, thighs, and legs to the heels, balls of the feet, and toes. Remarkably little muscular effort is expended to stand in place. Indeed, our large buttock, anterior thigh, and calf muscles are virtually unused when we stand still.
Instead of muscular contraction, the human bipedal stance depends more on the way in which joints are constructed and on strategically located ligaments that hold the joints in position. Fortunately for paleoanthropologists, some bones show dramatic signs of how a given hominin carried itself, and the adaptation to obligate terrestrial bipedalism led to notable anatomic differences between hominins and great apes.
These differences are readily identified in fossils, particularly those of the pelvis and lower limbs. Although we are bipedal, our pelvis is oriented like that of quadrupedal primates.
The early bipedal hominins assumed erect trunk posture by bending the spine upward, particularly in the lower back lumbar region.Other characteristics indicative of bipedalism in Ardipithecus include an increased tarsal region in each foot and a pelvic structure with muscle-to-bone attachment sites comparable to later, bipedal hominins.
In addition, the leg bone of Australopithecus anamensis from northern Kenya (– mya) attests to . Bipedalism: The Path to the Future. words.
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Human evolution Human evolution is the lengthy process of change by which people originated from apelike ancestors. Scientific evidence shows that the physical and behavioral traits shared by all people originated from apelike ancestors and evolved over a period of approximately six million years.
Human evolution is the evolutionary process that led to the suggests that the developmental and social adaptations evident in bonobos may be of assistance in future reconstructions of early hominin but split from the modern human lineage and followed a distinct evolutionary path.
The main find was a skeleton believed to be a woman of. Depending on the interpretation, this most probably suggests a spectrum of hominin bipedal adaptation from species incorporating a greater or lesser degree of arboreal climbing behaviour with terrestrial bipedalism, to full obligate bipedalism.
NARRATOR: According to Lieberman, small anatomical differences created large energy savings, setting our ancestors on the path to bipedalism, a path that would eventually lead to us.