How Did Scientiats Iniltially Know Lucys Baby Was a Hominin

When this minor-bodied, small-brained hominin was discovered, information technology proved that our early human being relatives habitually walked on two legs.

Its story began to take shape in late November 1974 in Ethiopia, with the discovery of the skeleton of a pocket-sized female, nicknamed Lucy.

More than than xl years later, Australopithecus afarensis is one of the best-represented species in the hominin fossil tape.

How Australopithecus afarensis changed our understanding of human evolution

Au. afarensis belongs to the genus Australopithecus, a grouping of minor-bodied and small-brained early hominin species (human being relatives) that were capable of upright walking simply not well adapted for travelling long distances on the ground.

Species in the australopith group - which likewise includes Au. africanus, Au. sediba, Au. anamensis and Kenyanthropus platyops - probably gave rise to ii more than recent hominin groups, Man and Paranthropus, earlier 2.5 one thousand thousand years ago.

Au. afarensis wasn't the first member of the group discovered - that was the Au. africanus from Due south Africa - merely its discovery confirmed our ancient relatives habitually walked upright, and that this characteristic of the human lineage occurred long before the development of bigger brains.

Australopithecus afarensis discoveries in the 1970s, including Lucy and the Laetoli fooprints, confirmed our aboriginal relatives were bipedal - walking upright on 2 legs - before big brains evolved. Replicas are on display in the Museum's Human Evolution gallery, aslope the skull of Kenyanthropus platyops, another hominin species that lived in East Africa during the same period.

The power to walk upright may take offered survival benefits, such as the power to spot dangerous predators earlier. Perhaps crucially, it left the hands free to do other tasks, such as carry food and use tools.

When did Australopithecus afarensis live?

According to the fossils recovered to date, Au. afarensis lived between 3.7 and three million years ago. This means the species survived for at least 700,000 years, more than twice every bit long as our own species, Homo sapiens, has been effectually.

Where did Australopithecus afarensis live?

Au. afarensis fossils have been unearthed in Ethiopia, Kenya and Tanzania.

Map showing sites in Tanzania and Ethiopia where Australopithecus afarensis fossils have been establish at Laetoli, Omo, Hadar, Woranso-Mille and Dikika. They have as well been institute at Lake Turkana in Republic of kenya.

Who is Lucy the Australopithecus?

Lucy was one of the get-go hominin fossils to get a household name. Her skeleton is effectually 40% consummate - at the time of her discovery, she was by far the virtually complete early hominin known.

On 24 November 1974, palaeoanthropologist Donald Johanson was exploring the ravines and valleys of the Hadar river in the Afar region of northeastern Ethiopia when he spotted an arm bone fragment poking out of a slope.

Johanson later recounted that his pulse quickened as he realised information technology belonged not to a monkey merely a hominin. As the squad found more and more fragments, they began to capeesh that they were uncovering an extraordinary skeleton. The full excavation took iii weeks.

Lucy'south skeleton consists of 47 out of 207 bones, including parts of the arms, legs, spine, ribs and pelvis, too as the lower jaw and several other skull fragments. Even so, virtually of the mitt and foot bones are missing.

A cast of Lucy, the fractional skeleton of an Australopithecus afarensis female found at Hadar, in the Afar region of Ethiopia. The fossil is slightly less than 3.eighteen million years old.

None of the bones were duplicates, supporting the determination that they came from a single individual.

The shape of the pelvic basic revealed the individual was female.

Lucy measured just i.05 metres tall and would take weighed around 28kg. Yet an erupted wisdom tooth and the fact that certain bones were fused suggested Lucy was a immature adult.

Reconstruction of Lucy'southward skull at the Naturhistorisches Museum Basel, based on a lower jaw bone and several other skull fragments. An erupted wisdom molar provided testify that Lucy was a immature adult when she died. © Pbuergler [CC Past-SA 3.0], from Wikimedia Commons

The affectionate nickname comes from the Beatles' song Lucy in the Heaven with Diamonds, which was ofttimes playing from the team'due south tape recorder back at campsite.

The formal attribution AL 288-1 is rarely used across academic journals. The skeleton is slightly less than 3.18 one thousand thousand years sometime.

A cast of Lucy on brandish in the Museum'south Human Evolution gallery. Her pocket-sized skull, long arms and conical rib muzzle are like an ape's, but she has a more human-like spine, pelvis and human knee due to walking upright.

Johanson thought Lucy was either a minor member of the genus Homo or a small australopithecine. Just after analysing other fossils subsequently uncovered nearby and at Laetoli in Kenya did scientists establish a new species, Australopithecus afarensis, four years after Lucy'southward discovery.

At the time, Au. afarensis was the oldest hominin species known, although far older species have since been found.

How did Lucy dice?

Researchers studied injuries to Lucy's bones to see whether they offered insights into how she died, publishing their findings in 2016.

CT scans revealed fractures in her shoulder joint and arms similar to those observed in people who fall from a swell tiptop, as if she reached out to break her autumn. They besides indicated that many of the breaks occurred perimortem, around the fourth dimension of death, rather than over time as the bones became fossilised.

The researchers believe the injuries observed were severe enough that internal organs could also have been damaged. Based on their bear witness, the team propose that Lucy died falling out of a tree.

Still, this conclusion is controversial and many scientists, including Johanson, say in that location are other plausible explanations for the breakages, such as being trampled by stampeding animals later decease.

Prof Donald Johanson, discoverer of Lucy and other Australopithecus afarensis fossils, contiguous with the skull of another early hominin. Image courtesy of Julesasu [CC0], from Wikimedia Eatables

Australopithecus afarensis characteristics

Au. afarensis possessed both ape-similar and human-like characteristics. The tiptop of its skull (the cranial vault) was slightly domed and its brain was comparable in size to a chimpanzee's. Its face projected outwards, less so in females than in males.

Some Au. afarensis skull specimens prove show this species possessed powerful chewing muscles.

Australopithecus afarensis skulls prove the species had a brain the size of a chimpanzee'due south, a projecting face up and powerful jaw muscles, used for chewing hard or tough institute cloth. This replica is on display at Cleveland Museum of Natural History. © James St John [CC Past 2.0], from Flickr

The small skull, long arms and conical ribcage were like an ape's, while the spine, pelvis and knees were more human-similar.

The smallest Au. afarensis adults weighed an estimated 25 kilograms, while the largest weighed well-nigh 64 kilograms.

This is a broad range, pointing to high sexual dimorphism - the difference in size and shape between males and females. Modern humans have a low level of sexual dimorphism and the ii sexes look very similar, whereas gorillas are very sexually dimorphic. The departure between Au. afarensis males and females is similar to the latter.

Model of a male person Australopithecus afarensis in the Vienna Natural History Museum showing the ape-similar long arms and the more man-like feet and upright stance © Wolfgang Sauber [CC Past-SA 4.0], from Wikimedia Commons

Au. afarensis is mostly depicted with torso hair as information technology was likely lost later in human development.

Australopithecus teeth

Au. afarensis has a number of distinctive dental features.

In some members of the species the tooth rows diverge slightly towards the back, forming a dental arcade (the office of the mouth where teeth sit down) that is neither parallel-sided as in modern apes nor more than rounded as in humans.

Australopithecus afarensis jaw replica. Exhibit in the Arppeanum, Helsinki. Image courtesy of Daderot [CC0 1.0], from Wikipedia Commons

The canine teeth of Au. afarensis are much smaller than those of chimpanzees, and they are narrower and differently shaped to those of the before Au. anamensis. The canine premolar honing complex has been completely lost - this is a feature present in chimpanzees and other apes outside of the hominin lineage, where the large and projecting upper canine teeth are sharpened against the lower third premolars. All known mod and fossil apes have this honing complex. Its absence, along with the presence of bipedalism, is idea to be characteristic of species on the hominin lineage.

The 3.v-million-twelvemonth-old Laetoli canine belonging to Australopithecus afarensis is the oldest hominin fossil in the Museum's drove. You lot can meet it in the Human being Evolution gallery.

How did Australopithecus afarensis move around?

Au. afarensis was competent at walking upright on ii legs, and skeletal features indicate information technology did so regularly. However, it may not accept walked in exactly the same way every bit we exercise or been able to walk long distances efficiently.

Anatomical features associated with upright walking are present in the spine, pelvis, legs and feet. These include a broad pelvis and a femur that is angled inward towards the articulatio genus so that the middle of gravity lies directly above the foot.

Reconstruction of Lucy's pelvis in the National Museum of Federal democratic republic of ethiopia. The broad pelvis of Australopithecus afarensis is an accommodation to upright walking. © Ji-Elle [CC By-SA 3.0], from Wikimedia Commons

Lucy and her species also retained some adaptations for climbing and hanging from copse. These features are seen in the shoulders, arms, wrists and hands.

It is likely that the species, particularly the smaller females, spent a significant amount of time moving around in trees. The larger males were probably less arboreal.

Au. afarensis may have foraged in the tree canopy equally well as on the ground, and probably retreated to the trees at night to avoid predators and for a good night's sleep. Chimpanzees and other apes are known to build nesting platforms in tree canopies.

Australopithecus afarensis probably slept in trees for safe, similar chimpanzees and orang-utans that build nesting platforms © Torsten Pursche/Shutterstock.com

Laetoli footprints - a snapshot in time

The site of Laetoli in Tanzania preserves the oldest known hominin footprints. Nearly 3.7 million years ago, a volcanic eruption covered the landscape with a layer of fine ash. Rain created a surface like moisture cement and, before it hardened, a diversity of animals wandered across it. Further eruptions covered the footprints they left backside, preserving them for posterity.

More than than 20 species left tracks, including rhinoceroses, giraffes and baboons.

In 1978, two years after the starting time animal prints were uncovered, palaeoanthropologist Mary Leakey excavated a 27-metre-long trail made past hominins, consisting of about 70 footprints. They were attributed to Au. afarensis, to this 24-hour interval the virtually likely candidate as merely this species has been constitute at Laetoli.

Replica in the Museum'southward Homo Evolution gallery of some of the footprints preserved at Laetoli, Tanzania, thought to be made by Australopithecus afarensis. The tracks bear witness two individuals walked side by side and a third followed behind. Their toes and manner of walking were more human than ape-like.

According to the close spacing of the footprints, the hominins who made them had brusque legs. The prints resemble those of modern humans, with an arch and a big toe aligned with the other toes. Their steps were likewise similar to those of modern humans, with the heel touching the ground commencement and weight transferring to the brawl of the foot before the toes button the foot off the ground. Biomechanical assay suggests the bipedal gait was non entirely modernistic though, and that the leg may take been slightly more bent at the genu as the human foot hit the floor.

The impressions left in the ash reveal that a pocket-sized group - with different sized feet - were walking from south to northward. At least one smaller individual was walking behind and stepping into the footprints made past a larger individual.

Near forty years subsequently, another set of footprints was found 150 metres from the original trail. These were fabricated by 2 individuals, 1 of whom was much taller and heavier, walking in the same management every bit the original group. Perhaps a unmarried social group made the two trails, peradventure a large male person walking with females and children.

A second gear up of footprints, as well most 3.seven 1000000 years erstwhile, were uncovered at Laetoli in 2015. It's quite rare to find footprints of hominins, the grouping to which humans and our ancestors and close relatives belong. The footprints at Laetoli are the only ones attributed to a species not in the genus Homo. © Masao et al (2016) eLife DOI: x.7554/eLife.19568, licensed under CC BY iv.0

What didAustralopithecus afarensis swallow?

Various lines of evidence suggest thatAu. afarensis ate a slightly different diet to that of earlier hominins.

Carbon isotope values in tooth enamel reveal thatAu. afarensis is currently the earliest hominin species showing bear witness for a more various diet that included savannah-based foods such as sedges or grasses, as well equally a more than traditional diet based on fruits and leaves from trees and shrubs.

Some of the anatomical changes compared to the before speciesAu. anamensis propose at that place was a modify in diet towards foods that were harder or tougher over time, asAu. afarensis has adaptations for heavy chewing.

Illustration by Maurice Wilson of the extinct hominin Australopithecus afarensis. This species walked upright simply retained the ability to climb trees. Information technology may have searched for food there, as well as on the ground.

DidAustralopithecus afarensis use tools?

Since our closest living relatives, chimpanzees, equally well as other apes and monkeys, have been observed making and using simple tools, it is likely that all hominins fabricated utilize of tools to some extent.

No tools accept yet been directly associated with Au. afarensis. All the same, Australopithecus species had hands that were well suited for the controlled manipulation of objects, and they probably did utilize tools.

The oldest known stone tools are around 3.3 million years old and were unearthed in Republic of kenya. These Lomekwian tools were made from volcanic rock and crafted into cores, flakes and potential anvils. AlthoughAu. afarensis is known from Kenya around this time, the near likely candidate for the toolmaker is another species called Kenyanthropus platyops, every bit specimens of this hominin have been institute close to where the tools were excavated.

A small number of brute basic plant at Dikika in Federal democratic republic of ethiopia, accept been reported as showing cut marks made by stone tools. They have been dated to about 3.4 million years ago and the team involved attribute the slaughter-house toAu. afarensis,as this is the only species known to live in the area at this fourth dimension. Even so, the conclusions are contentious. If they withstand scrutiny, this would be the earliest evidence of meat-eating behaviour past a hominin.

Important Australopithecus afarensis fossils

A number of other significant Au. afarensis finds have been fabricated in add-on to Lucy and the Laetoli footprints.

• Articulatio genus, AL 129 1a + 1b
  Uncovered in 1973, this was the commencement hominin fossil institute at Hadar in Ethiopia. The anatomy of the knee joint indicated it belonged to a species that walked on 2 legs and, at the time, information technology was the oldest bear witness of a biped. It encouraged Johanson'due south squad to return to the area, where they found Lucy the following year.

• Lower jaw, LH 4
  This jaw bone containing nine teeth was discovered in 1974 past Mary Leakey at Laetoli in Tanzania. Information technology was designated the type specimen for Au. afarensis, making it the specimen that officially represents the species and to which other potential Au. afarensis fossils need to be compared.

The Australopithecus afarensis type specimen - the LH 4 jaw bone from Laetoli, Tanzania, that officially represents the species. Credit: photo past F Spoor, courtesy of the National Museum of Tanzania.

• The commencement family, AL 333
  In 1975, more than 200 hominin fossils were unearthed from Hadar. They stand for at least 13 individuals, including 4 children. Scientists recall they were probably related. The specimens support the notion that Au. afarensis was significantly sexually dimorphic. Other than their size, the group showed nearly identical anatomical features, showing they were however species. Whatever disaster befell the group, it happened around 3.2 meg years ago.

• Kadanuumuu, KSD-VP-1/1
  Unearthed in Ethiopia between 2005 and 2009, this partial skeleton is similarly complete to Lucy just much older, dating to about iii.6 meg years ago. It belonged to a male person that was most 1.6 metres tall, about 30% bigger than Lucy. The nickname Kadanuumuu means 'Big Human being' in the Afar linguistic communication.

  Due to the lack of skull or dental parts to compare with the Au. afarensis type specimen, some scientists question whether Kadanuumuu tin can be assigned to this species.

Ethiopian palaeontologist Zeresenay Alemseged property the skull of Selam © Andrew Heavens [CC By-NC-ND 2.0], from Flickr

• Selam, an Australopithecus afarensis kid, DIK-ane-1
  An almost complete skeleton of a tiny Au. afarensis kid was found at Dikika in Ethiopia in 2006. More than five years of painstaking excavation revealed previously unknown aspects of the species. CT scans of the skull showed the kid's dental development was similar to a three-yr-old chimpanzee. From the lack of marks from predators or scavengers, it appears the child died naturally or in an blow and was quickly buried, perhaps by a flash flood.

This commodity includes information from Our Human Story by Dr Louise Humphrey and Prof Chris Stringer.

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Source: https://www.nhm.ac.uk/discover/australopithecus-afarensis-lucy-species.html

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