December 19, 2012
One-hundred years ago, on December 18, 1912, British paleontologist Arthur Smith Woodward introduced the world to a tantalizing fossil: England’s most ancient human ancestor, perhaps one of the world’s oldest hominids. Best known as Piltdown Man, the “discovery” turned out to be the biggest hoax in the history of paleoanthropology. It’s a scientific crime that researchers are still trying to solve.
Piltdown Man consists of five skull fragments, a lower jaw with two teeth and an isolated canine. The first fossil fragment was allegedly unearthed by a man digging in gravel beds in Piltdown in East Sussex, England. The man gave the skull fragment to Charles Dawson, an amateur archaeologist and fossil collector. In 1911, Dawson did his own digging in the gravel and found additional skull fragments, as well as stone tools and the bones of extinct animals such as hippos and mastodons, which suggested the human-like skull bones were of a great antiquity. In 1912, Dawson wrote to Smith Woodward about his finds. The two of them—along with Pierre Teilhard de Chardin, a Jesuit priest and paleontologist—returned to the Piltdown gravels to continue excavating. They found additional skull fragments and the lower jaw. The following year Teilhard de Chardin discovered the lone canine tooth.
Smith Woodward reconstructed the Piltdown man skull based on the available fossil evidence. His work indicated the hominid had a human-like skull with a big brain but a very primitive ape-like jaw. Smith Woodward named the species Eoanthropus dawsoni (Dawson’s Dawn Man). It was the first hominid found in England, and other anatomists took Piltdown as evidence that the evolution of a big brain was probably one of the first traits that distinguished hominids from other apes.
At the time of the discoveries, the field of paleoanthropology was still in its infancy. The only other hominid fossils that had been found by 1912 were Neanderthals in continental Europe and the even older Homo erectus of Indonesia. As additional fossils were discovered elsewhere, such as Africa and China, it became harder to see how Piltdown fit with the rest of the fossil record. The growing collection of hominid bones suggested upright walking was the first major adaptation to evolve in hominids with increases in brain size coming millions of years later after the emergence of the genus Homo. Finally, in the 1950s, it became clear why Piltdown was so odd: It was a fake.
In 1949, physical anthropologist Kenneth Oakley conducted fluorine tests on the Piltdown Man bones to estimate how old they were. The test measures how much fluoride bones have absorbed from the soil in which they’re buried. By comparing the fluoride levels to those of other buried objects with known ages, scientists can establish a relative age of the bones. With this method, Oakley determined Piltodwn Man wasn’t so ancient; the fossils were less than 50,000 years old. In 1959, anatomist Wilfrid Le Gros Clark and anthropologist Joseph Weiner took a closer look at Piltdown Man’s anatomy and realized the jaw and skull fragments belonged to two different species. The skull was most likely human while the jaw resembled an orangutan. Microscopic scratches on the jaw’s teeth revealed someone had filed them down to make them appear more like human teeth. And all of the bones had been stained to make them look old.
Since the truth about Piltdown Man was revealed, there have been many suspects implicated in the forgery. Dawson was the prime suspect. But he died in 1916, so scientists never had the chance to question his possible role in the hoax. Teilhard de Chardin, who found the isolated canine tooth on his own, is another possibility. One of Smith Woodward’s colleagues, Martin Hinton, may have also played a role. In 1978, workers found an old trunk of Hinton’s at the Natural History Museum in London. The trunk held teeth and bones stained in a similar way as the Piltodwn Man fossils. Despite much interest and speculation, no one has ever definitively tied any of these men to the hoax.
And now, a century after the announcement of Piltdown Man, scientists are still intrigued by the fake hominid’s origins. A team of 15 British researchers are using new methods to investigate the mystery. Radiocarbon dating and DNA testing will help identify exactly how old the bones are and confirm the jaw belongs to an orangutan. Chemical tests will also help the team pinpoint where the bones came from and whether they were all stained in the same way.
It will be several months before the analyses are complete. But if it turns out all the material was stained in the same way, or came from the same location, then it’s more likely that just one person was responsible for the scientific fraud. And that person is likely to be Dawson. It turns out that Dawson was responsible for at least 38 fake finds during his amateur fossil-hunting career, the Telegraph reports. Chris Stringer, an anthropologist at the Natural History Museum in London and one of the scientists investigating Piltdown, speculates in a commentary in Nature that Dawson may have committed such hoaxes in an effort to achieve scientific glory.
Stringer writes that Piltdown Man serves as a good reminder for scientists to “keep their guard up.” I think it also highlights the importance of open science in the field of paleoanthropology. The hoax wasn’t uncovered until scientists unconnected to the discovery analyzed the evidence. Today, numerous hominid species are known based on just a handful of fossils that only a handful of scientists have ever had the chance to study. In no way do I think some of these fossils might be fake. But giving other scientists greater access to the complete hominid fossil record will not only allow more errors to be detected but will also stimulate new interpretations and explanations of how our ancestors evolved.
And with that sentiment, I end my last Hominid Hunting post as I head off to a new job with Science News. I’ve enjoyed sharing my love of all things hominid with my readers, and I’ve appreciated all of the spirited feedback.
Ed. Note: Thanks, Erin, for all of your blogging the past couple of years! It’s been a thrill and best of luck to you going forward. — BW
December 12, 2012
South Africa plays a central role in the history of paleoanthropology. Anthropologists and other scientists of the 19th and early 20th century balked at the possibility that Africa was humankind’s homeland—until an ancient hominid was unearthed in South Africa in 1924. Since then, Africa has become the center of human evolution fieldwork, and South Africa has produced a number of iconic hominid fossils and artifacts. Here is a totally subjective list of the country’s most important hominid discoveries.
Taung Child: In 1924, anatomist Raymond Dart pried a tiny fossilized partial skull and brain from a lump of rock. The bones were the remains of a child. The youngster looked like an ape, but Dart also recognized some human qualities. He decided he had found a human ancestor that was so ancient it was still ape-like in many ways. (Later, scientists would determine the bones were nearly three million years old). Dart named the hominid Australopithecus africanus. The Taung Child, known by the name of the place where the fossils came from, was the first australopithecine ever discovered—and the first early hominid found in Africa. After the discovery, anthropologists who were searching for humanity’s origins in Europe and Asia switched their attention to Africa.
Mrs. Ples: Throughout the 1930s and 1940s, paleontologist Robert Broom led the efforts to find hominids in South Africa. He scoured the region’s limestone caves and quarries—the Taung Child came from a quarry—and was well rewarded for his efforts. Of the numerous fossils he uncovered (sometimes with the help of dynamite), his most influential find was a roughly 2.5-million-year-old skull of an adult female hominid now known as Mrs. Ples. Unearthed in 1947 at a site called Sterkfontein, the skull was well preserved and displayed the same mix of ape and human features seen in the Taung Child. Finding an adult version of A. africanus helped convince skeptics that the species was an ancient human ancestor. Some anatomists had thought Taung was just an ape and would have developed more pronounced ape-like features, and lost its human-like traits, as it grew up. Instead, Mrs. Ples showed that the species retained its mix of human and ape traits throughout life.
STS 14: Another one of Broom’s key finds is a set of well-preserved post-cranial bones that includes a pelvis, partial spine, ribs and upper thigh. Like Mrs. Ples, these fossils were found in 1947 at Sterkfontein and date to about 2.5 million years ago. The bones are officially known as STS 14 (STS refers to Sterkfontein) and presumably belonged to an A. africanus individual. The shape of the pelvis and spine are remarkably modern, and the find was some of the first evidence that early human ancestors walked upright on two legs.
SK 48: In addition to finding a trove of A. africanus specimens, Broom, along with his many assistants, discovered a new hominid species: Paranthropus robustus. The first hints of the species came in 1938 when Broom acquired a jaw fragment and molar that were much larger and thicker than any fossils belonging to A. africanus. Broom collected more of the unusual fossils and then hit the jackpot in 1950. A quarry worker found a nearly complete skull of an adult hominid that had giant teeth and a flat face. The fossil is officially called SK 48 (SK refers to the cave of Swartkrans where the skull was found). The collection of fossils with big chompers, which the hominids used to chew tough foods, was given the name P. robustus, which lived in South Africa about 1.8 million to 1.2 million years ago.
Little Foot: In the early 1990s, anthropologist Ron Clarke of South Africa’s University of the Witwatersrand found four small australopithecine foot bones at Sterkfontein. Later, Clarke and his colleagues discovered a nearly complete skeleton embedded in limestone that belonged to the foot. The researchers are still carefully chipping away at the rock to release the skeleton, dubbed Little Foot, but they have already noted that the individual has some characteristics not seen in any other known species of Australopithecus. But since the bones haven’t been fully studied and shared with other scientists, it’s hard to know where the hominid sits in the family tree, Science reported last year. It’s also hard to know exactly how old it is. Clarke’s team places the fossils at 3.3 million years old while other groups using different dating methods say Little Foot is more like 2.2 million years old. Science reported that Little Foot was expected to be fully liberated from its rocky enclosure sometime this year. As far as I know, that hasn’t happened yet.
Australopithecus sediba: The most recent major hominid fossil discovery in South Africa occurred in 2010. Lee Berger of the University of the Witwatersrand led a team that found two partial hominid skeletons at Malapa Cave. Dating to nearly two million years ago, the skeletons indicate that these hominids had their own unique style of walking and spent time both on the ground and in trees. X-ray scans of one of the skulls reveals that some aspects of the brain were more modern than in previous species. Berger and his colleagues therefore think the species, which they named A. sediba, could have given rise to the genus Homo.
Origins of Modern Behavior: Fossils aren’t the only major human evolution discoveries from South Africa. Several coastal cave sites have been treasure troves of artifacts that reveal when and how sophisticated behavior and culture emerged in early populations of Homo sapiens. There have been too many of these discoveries to single any one out. Some of these finds—such as red pigments used 164,000 years ago and shell beads dating to 77,000 years ago—are among the earliest evidence for symbolic thinking in our ancestors. Other artifacts, like 71,000-year-old projectile weapons, indicate early humans could construct complicated, multipart tools that require a lot of planning and foresight to make.
December 10, 2012
The Smithsonian Institution’s Human Origins Initiative counts seven species as belonging to the genus Homo. But that’s just a fraction of all the species that scientists have proposed for our genus. Over the years, as researchers have realized fossils from different groupings actually come from the same species, anthropologists have tossed out the names that are no longer valid. Last spring, I highlighted several of these now-obscure names, as well as some recently proposed species that are not universally accepted. Here’s a look at four more proposed species of Homo that you probably won’t find in human evolution text books or museum exhibits.
Homo antiquus: In 1984, Walter Ferguson of Israel’s Tel Aviv University declared that Australopithecus afarensis wasn’t a real species (PDF). At the time, the known fossils of A. afarensis came from the site of Hadar in Ethiopia and Laetoli in Tanzania. There was a lot of physical variation among the bones in this combined collection, but many anthropologists thought the diversity was simply due to size differences between male and female members of the species. Ferguson, however, believed the bones actually represented more than one species. Based on the size and shape of the molars, Ferguson concluded that some of the larger jaws at Hadar matched those of Australopithecus africanus, a species that had only been found in South Africa. Other jaws in the collection had smaller, narrower Homo-like teeth, he said. The roughly three-million-year-old fossils were too ancient to fit with any of the previously described members of the genus Homo, so Ferguson created a new species name—H. antiquus. Ferguson’s species splitting had a larger implication: If Australopithecus and Homo had lived side by side for hundreds of thousands of years, it was unlikely that australopithecines were the direct ancestors of Homo. Ferguson’s work must not have been convincing. Almost 30 years later, A. afarensis is still around and few people have ever heard of H. antiquus.
Homo kanamensis: Many of Louis Leakey’s discoveries have stood the test of time. H. kanamensis is not one of them. In the early 1930s, Leakey unearthed a hominid lower jaw at the site of Kanam, Kenya. The jaw resembled those of modern people in many ways, but was thicker in some places. Leakey determined the jaw should have its own name: H. kanamensis. At about half a million years old, the species was the oldest member of Homo yet found—except, the fossil wasn’t really that ancient. Subsequent geological studies at Kanam revealed that the jaw was only a few tens of thousands of years old. And the jaw’s unusual thickness was due to an abnormal growth, suggesting H. kanamensis was nothing more than a diseased Homo sapiens.
Homo capensis: In the early 1910s, two farmers stumbled across hominid fossils, including bits of a skull, near Boskop, South Africa. The bones were passed around to many anatomists—including Raymond Dart, who later discovered the first Australopithecus fossil—before ending up in the hands of paleontologist Robert Broom. Broom estimated the brain size of the skull (PDF): a whopping 1,980 cubic centimeters (the typical modern person’s brain is around 1,400 cubic centimeters). Broom determined that the skull should be called H. capensis, also known as Boskop Man. Other specimens from South Africa were added to the species, and some scientists became convinced southern Africa was once home to a race of big-brained, small-faced people. But by the 1950s, scientists were questioning the legitimacy of H. capensis. One problem was that the thickness of the original skull made it difficult to estimate the true brain size. And even if it were 1,980 cubic centimeters, that’s still within the normal range of variation for modern people’s brains, anthropologist and blogger John Hawks explained in 2008. Another problem, Hawks pointed out, was that scientists were preferentially choosing larger skulls to include in H. capensis while ignoring smaller skulls that were found in association with the bigger specimens. Today, fossils once classified as H. capensis are considered members of H. sapiens.
Homo rhodesiensis: If you have heard of any of the species on this list, it’s probably this one. Paleontologist Arthur Smith Woodward created the name H. rhodesiensis for a skull discovered in 1921 at Broken Hill, or Kabwe, in Zambia (once part of Northern Rhodesia). The fossil’s thick skull, sloped forehead and giant brow ridges made the species distinct from living people. Other robust African fossils dating to around 300,000 to 125,000 years ago were added to the species. However, this group of fossils has been known by many other names. Some anthropologists, for example, think the bones belong to early, more archaic members of our own species, H. sapiens. However, most researchers today lump H. rhodesiensis fossils with the more widespread species Homo heidelbergensis, which lived in Africa and Eurasia starting roughly half a million years ago and may have been the common ancestor of modern humans and Neanderthals.
November 26, 2012
Humans and Neanderthals split from a common ancestor roughly half a million years ago. While many anthropologists will tell you we don’t really know who that common ancestor was, others will say we do: the species Homo heidelbergensis, or something very much like it. An even smaller portion will point to another possibility: a controversial species called Homo antecessor.
H. antecessor, which first came to light in the 1990s, is known almost entirely from one cave in northern Spain’s Atapuerca Mountains. While working at the Gran Dolina site from 1994 to 1996, a team of Spanish researchers found 80 fossils belonging to six hominid individuals that lived roughly 800,000 years ago. The hominids’ teeth were primitive like those of Homo erectus, but aspects of the hominid’s face—particularly the shape of the nasal region and the presence of a facial depression above the canine tooth called the canine fossa—were modern, resembling features of modern people. The unique mix of modern and primitive traits led the researchers to deem the fossils a new species, H. antecessor, in 1997.
In 2008, the researchers expanded the timeline of the species . At another cave site in Atapuerca, Sima del Elefante, scientists unearthed a partial lower jaw, as well as a few dozen stone tools, dating to about 1.2 million years ago. Outside of Spain, the only other potential evidence of H. antessor
fossils are stone tools found at a nearly 800,000-year-old English archaeological site named Happisburgh that might have been made by the species.
H. antessor‘s discoverers—including José Bermúdez de Castro of Spain’s National Museum of Natural Sciences, Juan Luis Arsuaga of the Universidad Complutense in Madrid and Eudald Carbonell of the University of Tarragona—say the species’ similarities with modern people, and its age, make it the best known candidate for the common ancestor of Neanderthals and Homo sapiens. They suggest H. antecessor may have evolved from a population of H. erectus living in Africa more than 1.5 million years ago and then migrated to Europe, journalist Ann Gibbons reported in Science when H. antecessor was first announced. Although the species has yet to be discovered in Africa, an African origin for H. antecessor may be necessary if it was indeed the direct ancestor of modern humans, which all fossil evidence suggests originated in Africa. Furthermore, the researchers say H. heidelbergensis is too similar to Neanderthals to be a direct ancestor of modern humans. Instead, H. antecessor gave rise to H. heidelbergensis, which then gave rise to Neanderthals.
But many anthropologists are not on board with this scenario. One problem is that most of the known H. antecessor specimens represent children, Gibbons reported. Only two of the six individuals found at Gran Dolina are thought to be adults, about 20 years old. Since most of the features tying H. antecessor to modern people were found in juveniles—whose bodies and physical features change as they grow up and go through puberty—it’s possible that H. antecessor adults didn’t really look much like H. sapiens at all. And if that’s the case, then it’s hard to argue the species had an ancestor-descendent relationship with us. The issue won’t be settled until researchers find good examples of complete adult H. antecessor fossils.
September 19, 2012
I was intrigued when I saw this headline over at NPR’s 13.7 blog earlier this week: “A Neanderthal-Themed Park for Gibraltar?“ As it turns out, no one’s planning a human evolution Disney World along Gibraltar’s cliffs. Instead, government officials are hoping one of the area’s caves will become a Unesco World Heritage site. Gibraltar certainly deserves that distinction. The southwestern tip of Europe’s Iberian Peninsula, Gibraltar was home to the last-surviving Neanderthals. And then tens of thousands of years later, it became the site of one of the first Neanderthal fossil discoveries.
That discovery occurred at Forbes’ Quarry in 1848. During mining operations, an officer in the British Royal Navy, Captain Edmund Flint, uncovered an adult female skull (called Gibraltar 1). At the time, Neanderthals were not yet known to science, and the skull was given to the Gibraltar Scientific Society. Although Neanderthals were recognized by the 1860s, it wasn’t until the the first decade of the 20th century that anatomists realized Gibraltar 1 was indeed a Neanderthal. Additional Neanderthal discoveries came in the 1910s and 1920s at the Devil’s Tower rock shelter, which appeared to be a Neanderthal occupation site. In 1926, archaeologist Dorothy Garrod unearthed the skull of a Neanderthal child near flaked stone tools from the Mousterian industry. In all, archaeologists have found eight Neanderthal sites at Gibraltar.
Today, excavations continue at Gorham’s Cave and Vanguard Cave, where scientists have learned about the life and times of the most recent populations of Neanderthals. In 2006, researchers radiocarbon dated charcoal to estimate that the youngest Neanderthal populations lived at Gibraltar as recently as 24,000 to 28,000 years before the present. Clive Finlayson, director of the Gibraltar Museum’s Heritage Division, has suggested that Neanderthals persisted so late at Gibraltar because the region stayed a warm Mediterranean refuge while glacial conditions set in across more northern Europe. Ancient pollen data and animal remains recovered from Gibraltar indicate Neanderthals had access to a variety of habitats—woodlands, savannah, salt marshes and scrub land—that provided a wealth of food options. In addition to hunting deer, rabbits and birds, these Neanderthals enjoyed eating monk seals, fish, mussels and even dolphins on a seasonal basis.
As with most things in paleoanthropology, the Neanderthal history at Gibraltar is not settled. Some anthropologists have questioned the validity of the very young radiocarbon dates. Why the Neanderthals eventually died out is also a matter of debate. Further climate change in Europe, competition with modern humans or some mix of both are all possible explanations.