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Some of the oldest human remains ever unearthed are the Omo One bones found in Ethiopia. For decades, their precise age has been debated, but a new study argues they're around 233,000 years old.
ARI SHAPIRO, HOST:
In the late 1960s archaeologists discovered a set of familiar bones in Ethiopia - a skull bone, a lower jaw, parts of a torso. These were remains of Homo sapiens, early humans. That collection is known as Omo 1.
AILSA CHANG, HOST:
The contents of Omo 1 were initially thought to be around 200,000 years old, already some of the oldest human bones ever unearthed. But scientists have debated their precise age.
TIM WHITE: To understand how humans evolved in Africa, you need a time frame. And to construct that time frame, one needs to have accurate dating techniques. Unfortunately, we are just beyond the range of radiocarbon or C-14 dating. So you have to employ other techniques to determine the true age of these fossils.
CHANG: That's Tim White, professor of integrative biology at UC Berkeley. One of those techniques involves determining the age of the environment where the bones were found - in the case of Oma 1, a layer of volcanic ash.
CELINE VIDAL: There was a bit of controversy because the way Oma 1 was first dated was using an ash layer that was supposedly found just below. But it wasn't found where the fossils were actually found. It was found a bit further away.
SHAPIRO: Celine Vidal is a volcanologist at the University of Cambridge, and she says that the ash layer above Oma 1 was fine like flour. That's hard for scientists to date.
CHANG: But in a new analysis, Vidal and her colleagues found that the volcanic ash had the same chemical fingerprint as a massive volcanic eruption over 233,000 years ago.
VIDAL: That relies on the principle that every eruption has a unique chemical fingerprint, a unique chemical signature. So when it's possible to analyze a signature of an ash layer and if it correlates with the signature of an ash layer somewhere else and we know the age of one of the deposits, then we can guess indirectly the age of the deposits it's correlated with.
CHANG: Since Oma 1 was under that ash, Vidal thinks the bones are at least 33,000 years older than previously thought. The study was published in the journal Nature. Here's Tim White again.
WHITE: At what point did these people expand from Africa? What is their technology? What was the environment that they occupied? What was Africa like in those days? All of that depends on a strong geological framework but especially on a chronological framework. And that is what this new work has provided for one of the more complete skeletons from this time period.
SHAPIRO: In other words, if these human remains are much older than we thought, the story of humanity might be, too.
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The first discoveries of ancient human fossils. Neanderthals were the first ancient humans to gain scientific and popular recognition. Their fossils began to be found in Europe in the 1800s but scientists had no perspective or evolutionary framework by which to explain them. Decades passed before they were recognised as being a different and extinct form of ancient human. Opinions about the relationship between our own species and Neanderthals have continually changed. The early 1900s saw them as sub-humans, a stereotype that didn’t change until the 1950s when it was widely considered that they may be the ancestors of modern Europeans. New research in the 1980s led many to move them to a side branch of our family tree, a decision supported by the comparisons of the mitochondrial DNA of modern humans and Neanderthals in the 1990s and 2000s.
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1848
Gibraltar skull - Homo neanderthalensis. Discovered in 1848 in Forbe’s Quarry, Rock of Gibraltar
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1856
Neanderthal 1 skullcap - type specimen for Homo neanderthalensis. Discovered in 1856 in the Neander Valley, Germany. Although originally presented as an inferior human that inhabited Europe before modern people, some felt that the differences between Neanderthals and modern humans were due to pathology and disease. This marked the effective beginning of Palaeoanthropology as a science.
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1868
The remains of early modern humans found at Cro-Magnon in France.
These remains were the first firm evidence of the antiquity of our species, Homo sapiens.
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1886
Neanderthal skulls found in Spy, Belgium.
These finds supported the idea that Neanderthals were an ancient and distinct type of human, but exactly how they fit into our family tree was still debated.
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1891
Homo erectus skullcap found in Trinil, Java by Eugene Dubois, and described as a new species in 1894.
This specimen was originally named Pithecanthropus erectus as it was considered different enough from humans to be placed into a new genus. It was renamed Homo erectus in the 1940s, a species name that, in the opinion of most researchers, includes specimens from Java and China.
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1908
Homo heidelbergensis named as a new species after the discovery of a jaw in Mauer, Germany in 1907.
This species was originally dismissed as being too apelike for human ancestry, particularly after the Piltdown Man find. In the 1960s it was grouped with other similar skulls and called archaic Homo sapiens, but today the preference is to use the original scientific name and to give this species an ancestral position on the human family tree.
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1912
In a gravel-pit at Piltdown Common, Southern England, in 1912, amateur collector Charles Dawson ‘discovered’ what appeared to be the long-sought ‘missing link’ between apes and humans. This fortuitous find – nine pieces of a large-brained human skull and an ape-like lower jaw with two teeth – was readily accepted by the British establishment due to their belief that a large brain was one of the first human features to evolve. Although inconsistent with later discoveries, ‘Piltdown Man’s’ authenticity remained virtually unchallenged for 41 years.
In 1953, advanced analytical and dating techniques proved Piltdown Man to be a fake. The mandible was stained with potassium bichromate and the teeth had been filed down. Fluorine testing proved that the pieces of the skull were of different ages. This was confirmed in 1959 by carbon dating, which provided a date of about 600 years for the skull!
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1924
Discovery of the ‘Taung skull’ in South Africa, classified as Australopithecus africanus in 1925.
This fossil was clearly more ancient than earlier finds and anatomist Raymond Dart, who first analysed it, claimed it was a human ancestor. He was criticised very strongly by English scientists who believed in ‘Piltdown Man’. It was not until the 1950s that this species was fully acknowledged as belonging on the human family tree.
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1929
The first remains of Homo erectus found in China.
Chinese specimens were discovered in a cave at Zhoukoudian near Peking and named Sinanthropus pekinensis (‘Chinese man of Peking’). In the 1950s these specimens, and the ones from Java, were placed in the one species, Homo erectus.
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1938
Paranthropus robustus remains first discovered in South Africa.
Many of these fossils were originally given different names, which led to a confusing family tree. In the 1950s they were reclassified into the one species, Paranthropus robustus.
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1959
Remains of Paranthropus boisei found by the Leakeys in Olduvai Gorge.
This specimen OH5 (originally called Zinjanthropus boisei) was the first of our fossil ancestors to be given an accurate date with the new technique of radiometric dating. The date of 1.8 million years, obtained by potassium-argon dating, was announced in 1961.
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1964
Homo habilis announced as a new species after remains were discovered in Olduvai Gorge in 1960.
Although controversial, this fossil was the most primitive human to be classified into our genus. The family tree was still in a linear shape, with this species at the base
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1972
Originally thought to be Homo habilis, this specimen was reclassified as Homo rudolfensis in 1986 and made the type specimen of that species.
This specimen and another attributed to Homo habilis, KNM-ER 1813, are at the centre of the debate regarding which remains are attributed to that species. Homo habilis is a well-known but poorly defined species and scientific opinions about the attributed specimens vary widely. Scientists often disagree about naming fossil specimens as scientific names may be changed following new discoveries or there are different interpretations or new lines of investigation.
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1974
In 1978 this specimen, and a number of other remains from Laetoli, Tanzania, and Hadar, Ethiopia, was classified as a new species, Australopithecus afarensis.
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1975
This specimen was initially considered to be an African Homo erectus, but many now classify it as Homo ergaster.
This fossil was found in the same layer as a specimen of Paranthropus boisei, finally disproving the ‘single species’ theory that was popular at this time. Followers of this theory believed that only one hominin species could occupy an area at the one time and that the family tree was a single, evolving line moving through phases to modern humans. This find proved that the human family tree was more like a branching bush and that evolution was not linear.
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1984
Discovery in Kenya of an almost complete Homo ergaster skeleton, nicknamed the ‘Turkana Boy’.
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1996
Australopithecus bahreghazali described as a new species after remains were discovered in Chad.
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1995
Announcement of a new species Australopithecus anamensis after remains were discovered in Kenya.
It was not until 2016 that the public would see the face of this species with the discovery of the first and almost complete skull of A. anamensis, nicknamed MRD. Features suggest it was a separate species from A. afarensis and not a chronospecies as was previously believed.
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1995
Ardipithecus ramidus announced as a new species after fossil remains were found in Ethiopia.
At 4.4 million years old this species was the oldest of our ancestors found to date.
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1997
Homo antecessor announced as a new species after remains were found in Gran Dolina, Spain.
The remains are the oldest humans (genus Homo) found in Western Europe (dated to 800,000 years old) and may be the ancestors of modern humans and the Neanderthals. Their species designation is debated as many consider them Euopean H. heidelbergensis.
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1999
Australopithecus garhi announced as a new species after parts of a skull were discovered in Bouri, Ethiopia in 1997.
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2001
Kenyanthropus platyops announced as a new species after the discovery of a skull in Kenya in 1999.
There is some debate about the validity of this species. In 2003, scientist Tim White argued that the reconstructed skull of K. platyops may be a misreconstructed skull of Australopithecus afarensis.
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2001
Announcement of a new species, Orrorin tugenensis, after fossils were discovered in Kenya in 2000.
This is the earliest dated fossil (6 million years old) that may be an ancestor of humans. Its position on our family tree is still hotly debated.
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2001
Ardipithecus kadabba announced as a new species.
Remains of this species were found in Ethiopia over a number of seasons from 1997-2000.
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2002
Sahelanthropus tchadensis announced as a new species.
It was discovered in Chad in 2001 and dates to about 6-7 million years old. Scientists consider the find to be of major significance but debate its relationship to humans. It is very possible that it comes before the split between the human and chimp line, making it an ancestor of both branches.
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2004
Homo floresiensis, a type of dwarf human discovered on the Indonesian island of Flores, is announced as a new species. Fossils date from about 12,000 to 100,000 years old, making this a contemporary of modern humans. This species was not ancestral to modern humans and may be a descendant of Asian Homo erectus or a yet to be discovered Homo species.
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2009
Publication of study of Ardipithicus ramidus skeleton, first found in 1994. The skeleton provides the first substantial fossil evidence about the appearance of the last human-chimp common ancestor and confirms that living African apes do not much resemble this ancestor, as was commonly thought.
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2010
Publication of a new species Australopithecus sediba.
The first specimen was discovered in 2008 at Malapa in South Africa. Remains date to about 1.8 million years old. There is much debate about these remains and the species designation, with many considering them to be late A. africanus rather than a new species.
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2010
Discovery of the 'Denisovans'
Release of nuclear DNA analysis carried out on a finger bone and tooth from Denisova cave, Russia (found in 2008) reveals the remains come from a species that is neither Homo sapiens or Homo neanderthalensis. This suggests a third human species was still in existence between 48,000 and 30,000 years ago.
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2015
Homo naledi announced as a new species after the remains of at least 15 individuals were found in the Rising Star cave system in South Africa.
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2015
Fossil jawbones discovered in the Afar Region of Ethiopia in 2011 were announced as belong to a new species Australopithecus deyiremeda. Many consider these part of a variable population of A. afarensis.
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2016
Announcement that jawbone and teeth found in 2014 at Mata Menge in Flores are the ancestors, or early forms, of Homo floresiensis. The fosssils are about 700,000 years old.
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2018
Scientists identify, for the first time, an ancient individual that was a first-generation hybrid. DNA studies showed that a 90,000-year-old bone fragment found in the Altai Mountains, Russia, came from a female who had a Neanderthal mother and Denisovan father.