AUSTRALOPITHECINES: CHARACTERISTICS, POSSIBLE TOOL USE AND DIVERSITY

AUSTRALOPITHECUS

Australopithecus couple The earliest known hominins were for a long time were thought to come from the genus “Australopithecus” , which first appeared between 3 million and 4 million years ago. But now, after discoveries made in the 1990s and early 2000s, many scientists think the oldest hominins belong to another genus, “Ardipithecus”, that first appeared at least 4 million years ago and may be as old as six million years old. Some even older creatures that have been discovered may be hominins. A genus is a class of animals or plants that usually consist of more than one species.

There are many out there that still believe Australopithecus is the oldest hominin. They don’t regard Ardipithecus as a hominin. There are also some who don’t regard Australopithecus as a hominin either. Australopithecus means "southern ape" a reference to the fact that the first Australopithecus fossils were found in southern Africa. [Sources: Australopithecus, Rick Gore, National Geographic, February 1997; Australopithecus, Donald Johanson, National Geographic, March 1996]

Australopithecus mostly lived between two million and four million years. Some have said the genus may be as old as 7.5 million years. In February 1984 an Australopithecine jawbone with two molars — dated at 4 million years ago by nearby fossils and 5.4-5.6 million years ago by rocks — was found near Lake Baringo, Kenya.

The genus Australopithecus is considered the likely precursor of the genus Homo, to which modern humans belong. Though its cranium is comparable to a chimpanzee's, Australopithecus walked upright, as humans do. This was a surprise to anthropologists when the first Australopithecines were discovered because it had been assumed that big-brain of Homo was preceded by a big-brain ancestor, and having a big brain and walking upright evolved together. [Source: Wikipedia]

Australopithecus afarensis

Scientists have different theories about which hominins evolved into more developed species and which hominins lead to evolutionary dead ends. Some scientists believed that the “Homo” genus evolved from “Australopithecus afarensis” . Others believe it developed from “Australopithecus afarensis” . “Australopithecus Bosei” and “Australopithecus robustus” are believed to be evolutionary dead ends because they lived at the same time as “Homo” species. The various theories are difficult to prove.

Websites and Resources on Hominins and Human Origins: Smithsonian Human Origins Program humanorigins.si.edu ; Institute of Human Origins iho.asu.edu ; Becoming Human University of Arizona site becominghuman.org ; Hall of Human Origins American Museum of Natural History amnh.org/exhibitions ; The Bradshaw Foundation bradshawfoundation.com ; Britannica Human Evolution britannica.com ; Human Evolution handprint.com ; University of California Museum of Anthropology ucmp.berkeley.edu; John Hawks' Anthropology Weblog johnhawks.net/ ; New Scientist: Human Evolution newscientist.com/article-topic/human-evolution

Australopithecus Body Features, Size and Sex

Australopithecines (plural of Australopithecus) were short and stocky with apelike features such as long arms, thick waistlines and chimpanzee-like faces. They had short and stocky apelike bodies, and brains closer in size to a chimpanzee than a modern human. Males were about 1.37 meters tall and females 1.14 meters.

Judging from the well developed eye sockets and short nasal clefts of skulls, Australopithecines probably had keen eyesight but a poor sense of smell. It is believed they avoided danger by looking above the grasses for potential predators such as hyenas, lions and leopards.

Australopithecines appeared to sexually dimorphic, meaning that males were significantly larger than females, a trait shared by gorillas and orangutans. It is difficult to determine their age and lifespan because the rate in which they matured is not known.

In a study published in December 2007 in the journal Science, a team led Charles Lockwood of University College London theorized that dominant male “Australopithecus robustus” may have had large harems like modern gorillas do today. Based on the study of 35 fossilized A. robustus” remains, researchers found that adult males were considerably larger than adult females, a relationship usually associated with a dominate male and harem relationship in other animals. As it true with dominant males in other animal species male “A. robustus” kept on growing even after reaching adulthood while females stopped growing when they reached breeding age.

Australopithecus discovery sites

Australopithecines

At least eight species of Australopithecus (collectively known as Australopithecines) have been identified. It is not clear how they were related. Some are called robust australopithecines (australopiths) because they had heavy features and large jaws with powerful muscles for smashing and grinding tough food. The other species had heavy jaws but were more slightly built.

Lucy — of the species Australopithecus afarensis (which lived about 3.9 million to 2.9 million years ago at several sites in Ethiopia and Kenya) — and the Taung Child — of the species Australopithecus africanus (lived about 3.3 million to 2.1 million years ago in southern Africa) — are the most famous Australopithecus fossils. Catharine Paddock wrote in Medical News Today: “For a long time, it was thought that humans descended in a straight line from one pre-human species living 3 million to 4 million years ago. This theory was backed up by the fossil record - including the discovery of Lucy - until the end of the 20th century. [Source: Catharine Paddock PhD, Medical News Today, May 28, 2015]

“But then, the new century brought some surprises - researchers discovered Kenyanthropus platyops in Kenya and Australopithecus bahrelghazali in Chad. Both these species date from Lucy's period - challenging the idea that humans descended from a single hominin species. At first, scientists were highly sceptical following the discoveries in Kenya and Chad. But some started to change their view when in 2012, Dr. Haile-Selassie announced the discovery of the 3.4 million-year-old Burtele partial foot fossil, confirming the likelihood of multiple hominin species living at the same time 3 million to 4 million years ago.”

Different Australopithecines

Australopithecus
1) Australopithecus africanus
a) A. africanus (lived about 3.3 million to 2.1 million years ago in southern Africa)
b) A. deyiremeda (lived about 3.5 -3.3 million years ago in northern Ethiopia)
c) A. garhi (lived about 2.5 million years ago in Ethiopia)
d) A. sediba (lived about 2 million years ago in southern Africa)

2) Also called Paranthropus (lived about 2.6 million to 1.1 million years ago)
a) P. aethiopicus (lived about 2.5 million years ago in southern Ethiopia)
b) P. robustus (lived about 2 million to 1.2 million years ago in southern Africa)
c) P. boisei (lived about 2.4 million to 1.4 million years ago in Olduvai Gorge in Tanzania)

3) Also called Praeanthropus
a) A. afarensis (lived about 3.9 million to 2.9 million years ago at several sites in Ethiopia and Kenya)
b) A. anamensis (lived about 4.2 million to 3.9 million years ago at several sites in Ethiopia and Kenya)
c) A. bahrelghazali (lived about 3.6 million years ago in Chad)

Australopithecines

Complexity of the Hominid Scene 3 Million Years Ago

Pete Spotts wrote in Christian Science Monitor: “New fossils from Ethiopia are providing fresh evidence that some 3 million to 4 million years ago, ancestors to modern humans may have been more diverse than previously thought. That diversity would have led to an inadvertent test to see which species was best able to weather changes in climate and habitat during that period, some researchers suggest. So far, that would appear to be Australopithecus afarensis, represented by its most famous example, Lucy, discovered in 1974 by Donald Johanson and Tom Gray. [Source: Pete Spotts, Christian Science Monitor, May 27, 2015]

“But Lucy and her species were not the only Australopithecine on the block. Over the years, researchers have reported uncovering two additional species from this period. If this latest discovery holds up, it would bring to four the number of known Australopithecus species living within this million-year span. These species range from Ethiopia to Chad. The research team that found the new fossils – upper and lower jaws that included teeth – have classified the find as belonging to a new species of hominin, a subset of hominids that includes modern humans and our direct ancestors. The researchers suggest that the new species, which they have dubbed Australopithecus deyiremeda, was a close relative to A. afarensis. The team's analysis appeared the journal Nature.

“A. deyiremeda's remains were found at a site in Ethiopia's Afar region known as Woranso-Mille, about 22 miles north of another site rich in A. afarensis fossils – pointing to the possibility that the two species roamed the same general region at about the same time. With several Australopithecus species living in eastern and central Africa in the same general period, "we're looking at hominins who are potential candidates as human ancestors," says Henry Bunn, a paleoanthropologist at the University of Wisconsin at Madison. During this period, known as the middle Pliocene, the climate was getting cooler and drier. Vegetation and food resources were changing.

bones with tool marks from Dikika Ethiopia

“Looking at these Australopithecines, "you could almost think of them as ecological experiments as populations try to exploit new habitats and new resources successfully," says Dr. Bunn, who was not a member of the research team. "Most of those species went extinct."

In the past, researchers had broken the last 5 million years of hominin evolution into blocks of 1 million to 2 million years, he explains. Based on the fossil evidence available at the time, "you only had one species per block of time," he says. At about 2 million years ago, with the emergence of the genus Homo, hominins became more diverse.

With Lucy and subsequent discoveries, it now appears that the middle Pliocene also hosted a diverse array of hominins that included at least one additional group beyond Australopithecines – a group represented by Kenyanthropus platyops. The newly discovered jawbones and teeth – dated to between 3.5 and 3.3 million years ago – shared some characteristics with A. afarensis and others with K. platyops. This period also coincides with the appearance of the earliest stone tools yet found, a discovery announced last week in another paper in Nature.

“The new species is yet another confirmation that Lucy’s species, Australopithecus afarensis, was not the only potential human ancestor species," according to Yohannes Haile-Selassie, curator of physical anthropology at The Cleveland Museum of Natural History who headed the team making the discovery. “Current fossil evidence from the Woranso-Mille study area clearly shows that there were at least two, if not three, early human species living at the same time and in close geographic proximity,” he said in a prepared statement.

Laetoli Footprints

A series of 3.6 million-year-old footprints left in volcanic ash by an early hominin were discovered in Laetoli, Tanzania. The 69 prints were made by two adults that appear to have walked side by side. The two sets of prints parallel each other, about a foot apart. The Laetoli footprints were likely made by Australopithecus afarensis individuals. They made headlines in the 1970s as the earliest clear evidence of upright walking by our ancestors.

Laetoli footprints One set seems to be made by a large male, and the other by a smaller female. Inside the larger prints are prints from a third individual, possible a child. At one point the prints are so close together the hominins could have been holding hands. At another place the small one seems to be walking behind the large one. At another point the smaller one halted in mid stride, perhaps to turned around and look at something.

The Laetoli prints provides the best evidence that early hominin walked like modern humans — body upright, legs striding side by side. Unlike the feet of chimpanzee, which have a splayed toe that separates from the foot like a thumb, the Laetoli tracks are made by feet with all the toes parallel to the axis of the foot (the same as humans).

The large gap between the large toe and the rest of the toe meant the Laetoli creature no longer spent much time climbing trees. There was also no evidence of knuckle walking of any kind. Little Foot, a 3- to 3.5- million-year-old fossil foot from a “ Australopithecus africanus” foot found in South Africa, has an ape-like splayed toe and humanlike ankle which shows that feet ideal of bipedalism evolved slowly.

Oldest Stone Tools

In 2009, 3.4-million-year-old bones — found in Dikika, Ethiopia, near site where a Lucy-like hominin was discovered — with slashes, parallel marks and other cut marks that appear to have been made with stone tools, was presented as evidence that stone tools were produced more than 800,000 years than earlier thought and they could have been made by a possible human ancestor such as Lucy (Australopithecus afarenis). Unlike 2.5-million-year-old stone flakes found Ethiopia in 1997, which were mostly sharp cutting edges or the remains of the tool-making process, the stone tools that made the marks in Dikika were likely used as they were found. Detailed analysis of the cut marks on the bones seemed to indicate they were significantly different from tooth and claw marks made by predators. One of the marks was embedded with a small fragment of stone, according to a report in the journal, Nature.

Stone tools found from 2011 to 2014 at Lake Turkana in Kenya have been dated to be 3.3 million years old, and predate the genus Homo by half million years (the oldest known Homo fossil is 2.8 million years old). The stone tools may have been made by Australopithecus afarensis who lived 3.9 to 2.9 million years ago. The dest known example of this species is Lucy, which inhabited Ethiopia around the same time as the date of the oldest stone tools. The tools were dated based on the volcanic ash layers near the sediments they were found in. The volcanic layers are dated based on their magnetic signature (whether they pointed north or south due, calibrated using the reversal of the magnetic poles). [Source: Wikipedia]

Charles Q. Choi of Live Science wrote: “Researchers tried using stones to knock off and shape so-called flakes or bladesto better understand how these stone artifacts might have been made. They concluded the techniques used may represent a stage between the pounding used by earlier hominins and the knapping of later toolmakers. "This is a momentous and well-researched discovery," paleoanthropologist Bernard Wood, a professor of human origins at George Washington University, "I have seen some of these artifacts in the flesh, and I am convinced they were fashioned deliberately." Analysis of carbon isotopes in the soil and animal fossils at the site allowed the scientists to reconstruct what the vegetation there used to be like. This led to another surprise — back then, the area was a partially wooded, shrubby environment.” [Source: Charles Q. Choi, Live Science, May 20, 2015 ]

Are Hobbits Evidence That Australopithecus Left Africa?

The origin of Homo floresiensis (the hobbits of Indonesia) raises some interesting questions, one being that they could be descendants of predecessor of homo erectus —homo habalis or even a Australopithecus species — and this in turn could mean homo habalis or Australopithecus species could have emerged from Africa before Homo erectus.

Oldawan chopper

Deborah Netburn wrote in the Los Angeles Times: “One hypothesis posits that Homo floresiensis descended from the large-bodied hominin Homo erectus that lived between 1.89 million and 143,000 years ago. Scientists say it is possible that Homo erectus may have arrived on Flores from Java, perhaps after being washed out to sea by a tsunami. Over time, this species began to shrink on its new island home – a relatively common phenomenon known as island dwarfism. “Lots of animals that end up on islands get smaller for a variety of reasons like limited food sources, or because there are no large predators to stay big for,” said Karen Baab, a paleoanthropologist at Midwestern University in Glendale, Ariz., who was not involved in the study. “We even see it in modern humans in certain environments that are home to pygmy populations.” [Source: Deborah Netburn, Los Angeles Times, June 8, 2016 */]

“The other hypothesis states that Hobbits descended from smaller and more ancient hominins like Australopithecus africanus or Homo habilis that were already diminutive at the time they reached the island. Both theories have challenges. One might accept that Homo erectus grew smaller in stature by two-thirds over time. After all, a smaller body is easier to feed. But for some scientists, it is hard to believe that it made evolutionary sense for its brain to shrink by half. Losing brain power doesn’t seem like a likely evolutionary development. On the other hand, if you buy that Homo floresiensis was descended from Australopithecus or Homo habilis, then you have to explain how either of these species made their way to Indonesia when their remains have never been found outside of Africa. */.

A bone study published in 2017 in the Journal of Human Evolution showed there was nothing to support claims that Homo floresiensis evolved from Homo erectus, which scientists say was an ancestor of modern humans, and thus did not have any direct links modern humans. Teeth similarities had been suggested as evidence that homo erectus and hobbits were linked.

Melissa Davey wrote in The Guardian: “The study, led by the Australian National University researcher Dr Debbie Argue from the school of archaeology and anthropology, found there was no evidence Homo floresiensis evolved from the much larger Homo erectus, the only other early hominin known to have lived in the region. It was one of several theories about the origins of the “hobbit” species. Since it was discovered, researchers have tried to determine whether Homo floresiensis was a species distinct from humans. [Source: Melissa Davey, The Guardian, April 21, 2017]

“The findings add support to the theory that the species evolved from one in Africa, most likely Homo habilis, and that the two species shared a common ancestor. It was possible that Homo floresiensis evolved in Africa and migrated, or the common ancestor moved from Africa and then evolved into Homo floresiensis somewhere, the researchers concluded. Prof Mike Lee of Flinders University and the South Australian Museum used statistical modelling to analyse the data collected by the researchers. He said the findings were clear. Homo floresiensis occupied a very primitive position on the human evolutionary tree,” Lee said. “We can be 99 percent sure it’s not related to Homo erectus and nearly 100 percent it isn’t a malformed Homo sapiens.” |=|

There is a good evidence that a relatively large human that lived 700,000 years ago and shrunk quickly and stayed that size ago is an ancestor of Homo floresiensis according to two studies published in Nature in June 2016. Marlowe Hood of AFP wrote: “A modest haul of teeth and bones from an adult and two children has bolstered the theory that Homo floresiensis arrived on Flores island as a different, larger species of hominin, or early man, probably about a million years ago. And then, something very strange happened. These upright, tool-wielding humans shrank, generation after generation, until they were barely half their original weight and height. [Source: Marlowe Hood, AFP, June 9, 2016 \^/]

Image Sources: Wikimedia Commons except Laetoli footprints from Sciencephoto and Dikika bones from Wired

Text Sources: National Geographic, New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Nature, Scientific American. Live Science, Discover magazine, Discovery News, Times of London, Natural History magazine, Archaeology magazine, The New Yorker, Time, Newsweek, BBC, The Guardian, Reuters, AP, AFP and various books and other publications.

Last updated April 2024