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Australopithecus: Definition, Characteristics & Evolution

Australopithecus: Definition, Characteristics & Evolution
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  • 0:01 Who Was Australopithecus?
  • 0:39 Evolution
  • 1:39 Australopithecine…
  • 2:17 The Genus Australopithecus
  • 6:38 Lesson Summary
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Lesson Transcript
Instructor: Nicholas Gauthier
Our recent ancestry includes a variety of upright-walking apes that have mastered fire, tools, and the beginnings of language. Peer back into the mists of time to uncover the secrets of our earliest walking ancestors.

Who Was Australopithecus?

Australopithecus literally means 'southern ape.' It is an extinct genus of members of the human family tree. Scientists generally accept five species: A. afarensus, A. africanus, A. anamensis, A. garhi, and A. sediba, as belonging to the genus.

We'll take a look at each of the Australopithecine species in turn, covering their time of emergence in the fossil record, probable place in our family tree, and overall traits. But first, let's look at an overview of the human family tree.

Evolution

Humans are just one ape on the primate family tree. We, along with the other apes, split off from chimps around six or seven million years ago. After that, various upright walking apes from several genera evolved. All of the upright-walking species, including us, are called hominids, from family Hominidae.

We are Homo sapiens, belonging to the genus Homo. There are at least several extinct members of the genus Homo. One is Homo neanderthalensis, with whom we have interbred, while another is Homo habilis, which is known for being one of the early stone tool users.

Australopithecus is another hominid genus that evolved earlier than Homo. In fact, genus Homo appears to have evolved from genus Australopithecus. The hominid family tree is grouped by genus, or by related genera in the case of the earliest grouping. The exact relationships between these species are not well understood and doubtless many more are waiting to be discovered.

Australopithecine Characteristics

The Australopithecus species, referred to as Australopithecines, had features that were both human-like and ape-like. Their brains were smaller and more in the range of the brains of modern apes. They tended to have longer arms that seemed well-suited to climbing. In general, their facial features looked more ape-like than human, with sloping faces and jutting jaws.

However, their skeletons show that they walked upright. Furthermore, the teeth of some species were more like human teeth. Perhaps more importantly, they showed that our ancestors started walking upright before the evolution of larger brains.

The Genus Australopithecus

Living some 4.2 to 3.9 million years ago, A. anamensis is the oldest known Australopithecine. A. anamensis had a jaw like a chimp, but teeth that were clearly hominid. While little of its skeleton has been found, it is thought to have climbed trees like other Australopithecines, as well as walked upright.

Originally discovered in 1965 by a Harvard team, more fossils were found in the decades since. The finds range from Lake Turkana in Kenya to Northeast Ethiopia. Anthropologist Meave Leakey was responsible for officially naming the species in 1995.

Known affectionately to the public as the Lucy fossil, A. afarensis ranged through Ethiopia, Kenya, and Tanzania from 3.85 to 2.95 million years ago. The species is thought to be either a direct ancestor of genus Homo or a close relative of such an ancestor. It is also the first species that made scientists realize that upright walking evolved before large brains.

A. afarensis walked on two legs but still had the long arms for climbing trees. Its brain size was about a third of human brain size. Its teeth were larger than human teeth, but smaller than ape teeth, and it had a protruding ape-like jaw. Afarensis matured at a faster rate than humans.

Famous footprints in fossilized volcanic ash at the Laetoli site in Tanzania are thought by many scientists to have been made by A. afarensis. There are over 900 fossils representing this species, making it one of the best-known hominid species.

Discovered in 1924, the Taung Child was the first evidence of early human species in Africa. The name Australopithecus africanus literally means 'southern ape of Africa.' It was named for the fact that it lived in modern-day South Africa. It was the first of many hominid species to be discovered on the African continent. While not immediately accepted as part of the human family tree, A. africanus is one of the most talked-about species, particularly because of the way that the Taung Child is thought to have died.

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