Was Australopithecus afarensis the first bipedal hominin?

Was Australopithecus afarensis the first bipedal hominin?

Introduction

Australopithecus afarensis is one of the best known early human species which is recognized for its extended living of more than a million years. A. Afarensis is from the genus of Australopithecus, which was composed of a collection of hominin species. It is also referred to as southern ape from afar. The word afarensis is centered on the location where the first fossils of the species were found in the Afar depression in Ethiopia. This species was named in 1978 by T. White and Dr. Johanson. It is a notable species due to the famous lucy specimen, which got its genus name, southern ape, from the discovery of the first fossils. This species is categorized as a glacial form of australopith in the changing east African landscape, which covered a wide geographic area. The species was found between 3.9 and 2.9 million years ago in Ethiopia, Kenya, and Tanzania.

Discovery of Australopithecus afarensis

In 1970, fossil hunting teams were looking for evidence of ancient human ancestors in Africa. One of the groups was led by Donald Johanson was located in Ethiopia while the other group headed by mary Leakey was about 1500 kilometers away at laetoli in Tanzania. The first species was discovered from a specimen called lucy, which was approximately 3.2 million years old. These fossils were found in the afar triangle region in Ethiopia. The two teams discovered fossils that had similar characteristics and ages, but they did not match any of the findings which had been made previously. The species was therefore given its specific name A. Afarensis. Other regions with afarensis remains were Omo, Fejej, and Maka in Ethiopia and lothagam and Koobi fora in Kenya.

The footprints of afarensis were discovered in Tanzania in 1974 by mary Leakey. The fossils of the species were also found a few meters away, and it was therefore presumed that they had left the prints. The prints were made after a volcanic eruption and later covered by a subsequent eruption that preserved the footprints until they were discovered. They appeared like those of two people walking side by side with a pair of the prints looking more massive than the others. The footprints not only indicated that the a. Afarensis was bipedal, walking upright, but also that the species did not have divergent toes that were associated with apes. The footprints were the most significant evidence that the species were walking upright. Just like in modern humans, the prints illustrated that the heel was the first part to hit the ground. The big toe was also aligned with the other toes and marked a deep impression representing how each step ended with the toes being pushed downwards.

Characteristics of Australopithecus afarensis

The southern ape had both human as well as ape characteristics. The members of this species had face proportions similar to those of an ape, approximately a third of human braincase and long, hairy, and healthy arms with curved fingers adapted for climbing trees. The pelvis and lower limb of this species indicated that they were fully bipedal. This species also had small canine teeth just like other early humans, and they stood on two legs, making it possible for them to walk in upright. The species had replaced the opposable big toe with an arched foot, which made it possible for them to walk in nearly the same manner as the modern humans. Based on the analysis of fossilized laetoli footprints and metatarsals, the afarensis feet must have had human like-arch feet. The lucy specimen represents a gradual bipedal transition between the chimpanzees and modern humans. However, the forearms were longer with long curved fingers and toes, which indicated that the species used to climb trees for forage or refugee from predators at night. According to, their adaptations for living on the ground and trees enabled them to survive longer as they could quickly adapt to the changes in climate and environment.

Just like chimpanzees, the offsprings of the A. Afarensis grew rapidly after birth and reached adulthood faster than modern humans. The A. Afarensis, therefore, had a shorter period growing up and thus having less time to socialize or acquire parental guidance while growing up. The cognitive ability of this species was similar to that of other apes. Its distinct characteristics included a bony ridge over the eyes, low forehead, flat nose with no chin, teeth resembling those of a human being, pelvis, and leg bones, which are similar to those of the modern human and females who were smaller in size than the males. Australopithecus were the immediate ancestors of humans and were both categorized as members of the same biological tribe referred to as the hominin. They were both habitually bipedal, walking upright with two lower limbs. This species emerged immediately after the divergence from the common hominid ancestors with bonobos and chimpanzees. The species is considered as a direct ancestor of humans as well as that of later species of Australopithecus and all species in the genus of Paranthropus.

First bipedal hominin

The first bipedal hominin was Australopithecus anamensis. They are believed to have lived 4.2 to3.9 million years ago. Even though little is known about this species due to the scarcity of their fossils, it was discovered that the species were bipedal. The shapes of the limbs indicated that it was bipedal even though it was efficient in climbing trees. The Australopithecus afarensis were believed to have lived after the anamensis evolving from the earlier apes species. The excellent traits in afarensis indicated bipedalism suggests that bipedality was present in the species that evolved to become afarensis. The characteristics attributed to locomotion were more human than ape-like, which stated that they were in a more advanced stage.

How Australopithecus afarensis changed our understanding of human evolution

1. Afarensis was not the first species to e discovered that was from southern Africa, but its discovery confirmed that they were our ancestors as they walked upright using two lower limbs. This feature, which is common to modern humans, occurred before the evolution of the brains of the species.

The discovery of this species in the 1970s, including lucy, was proved that the ancient ancestors began walking in two legs even before their brains evolved. The skeletal features from the species indicated that it moved on two legs regularly. The anatomical features which stated that the species walked upright were present in the pelvis, feet, legs, and spine. The pelvis was broad, and femur angled inwards towards the knee such that the center of gravity was directly above the foot.

Au. Afarensis ate a different diet from that of the earlier hominins. The carbon isotopes values present in the tooth enamel of the species indicated that afarenisis were the earliest hominin species that took a different diet, which included grasses and sedges as well as fruits and leaves from shrubs and trees. Unlike the small canine teeth, the molars were more extensive than those of earlier hominin and had thicker enamel. Over time, the species changed its diet into other foods, which were harder and more robust. This is evident from the adaptations discovered in the species for heavy chewing. The species is believed to have used simple tools which included sticks and other non-durable materials which were found near the fossils. They might have also used stones even though there is no proof of shaped stones or any modified rocks. Based on the evidence collected, it is believed that the species lived in small social groups, which consisted of a mixture of males, females, and children.

Conclusion

Australopithecus Afarensis is regarded as the direct ancestor of modern humans. It is also considered as a direct ancestor of the other species of Australopithecus. The footprints of the species were the first evidence that illustrated that the afarensis walked upright. The fossils also indicated that the species were bipedal. The species was not the first bipedal hominin as the amenisis, which existed before the afarenisis were also bipedal. Besides waling like the modern human, the afarensis had features that resembled that of an ape, including a small brain, long jaw, and the adaptation of limbs for climbing trees.

References

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Raichlen, D.A., Gordon, A.D., Harcourt-Smith, W.E., Foster, A.D., and Haas Jr, W.R., 2010. Laetoli footprints preserve earliest direct evidence of human-like bipedal biomechanics. PLoS One, 5(3), p.e9769.

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Harcourt-Smith, W.E., 2007. Origin of bipedal locomotion. Handbook of Paleoanthropology, pp.1919-1959

Lovejoy, C.O., Suwa, G., Spurlock, L., Asfaw, B., and White, T.D., 2009. The pelvis and femur of Ardipithecus ramidus: the emergence of upright walking. Science, 326(5949), pp.71-71e6.