วันจันทร์ที่ 22 กุมภาพันธ์ พ.ศ. 2559

We might finally know why the Maya abandoned their impressive limestone cities about 1,000 years ago
When the Spanish conquistadores sailed for Central America in 1517, their goal was to vanquish the resident Maya civilisation. But the colonists arrived to find that much of their work had been done for them.
By the time the Spanish made landfall, the Maya’s political and economic powerhouse has vanished
The Maya’s towering limestone cities – a classic feature of one of the ancient world’s most advanced societies – were already being reclaimed by the jungle.
The question of how the Maya met their end is one of history's most enduring mysteries. The Mayapeople survived; they even managed to stage a long resistance to European rule. But by the time the Spanish made landfall, the political and economic power which had erected the region's iconic pyramids, and had at one time sustained a population of some two million people, had vanished.
El Castillo at the Mayan ruins at Tulum Quintana Roo Mexico
El Castillo at the Mayan ruins at Tulum Quintana Roo, Mexico (Credit: 24BY36/Alamy)
The first Maya sites were built during the first millennium BC, and the civilisation reached its height around AD600. (In the chronology of Mesoamerica, the Maya sit between the earlier Olmec and later Aztec civilisations). Archaeologists have uncovered thousands of ancient Maya cities, most of which are spread across southern Mexico's Yucatan peninsula, Belize and Guatemala. 
It’s likely that still more Maya ruins lie hidden beneath the region’s thick tropical forest.
The Maya had a strong grasp of mathematics and astronomy and used the only known written script in Mesoamerica
After about 200 years of serious archaeological study, we know enough about the Maya to be suitably impressed. Their distinctive art and architecture prove that these were master craftspeople.
The Maya were also intellectually advanced. They had a strong grasp of mathematics and astronomy, which they used to align their pyramids and temples with the precession of planets and the solar equinoxes. And they used the only known written script in Mesoamerica, a bizarre-looking set of characters known as Maya hieroglyphs.
The marvels the Maya left behind have earned them an enduring mystique. But the way the civilisation met its end is every bit as curious.
Let’s start with what we know. Around AD850, after centuries of prosperity and dominance, the Maya began to abandon their great cities, one after another. In less than 200 years, the civilisation had slumped to a fraction of its former glory. There would be later isolated resurgences, but the grandeur of the Maya’s heyday was gone forever.   
Apart from its dramatic scale, what makes the Maya collapse so striking is that, despite decades of study, archaeologists still cannot agree on what caused it. As with the Roman Empire, there probably wasn’t one single culprit for the Maya’s downfall. But the nature of their decline leads some researchers to believe that the Maya civilisation fell victim to a major catastrophe – one able to topple city after city in its wake.
Archaeologists still cannot agree on what caused the Maya collapse
Archaeologists still cannot agree on what caused the Maya collapse (Credit: Travelstock44/Alamy)
There are abundant theories about what finished off the Maya. There are the old favourites – invasion, civil war, collapsing trade routes – but ever since the first Central American ancient climate records were pieced together in the early 1990s, one theory has become particularly popular: that the Maya civilisation was ultimately doomed by a period of severe climate change.
In the centuries immediately before the Maya collapse – the so-called “Classical Age” between about AD250 and 800 – the civilisation boomed. Cities flourished and harvests were good. Climate records (which mostly come from the analysis of cave formations) show that during this time the Maya area had received relatively high rainfall. But the same records show that, starting in about AD820, the region was ravaged by 95 years of punctuated droughts, some of which lasted for decades.
Most of the Classic Maya cities fell between AD850 and 925 – largely coincident with a century of drought
Ever since these droughts were first identified, researchers have noticed a striking correlation between their timing and that of the Maya collapse: most of the Classic Maya cities fell between AD850 and 925 – largely coincident with the century of drought. And while a simple correlation isn’t enough to close the case, the tight fit between the droughts and the downfall leads many experts to believe that the 9th Century climate shift might somehow have caused the Maya’s demise. 
But attractive as the drought explanation is, one piece of evidence has been standing in its way. Because, while most Maya cities declined as the climate dried, not all did. 
This northern resurgence flies against the drought theory of the Maya’s demise
The Maya cities which fell during the 9th Century droughts were mostly located in the southern portion of their territory, in modern day Guatemala and Belize. In the Yucatan peninsula to the north, however, the Maya civilisation not only survived through these droughts, it then began to flourish. 
While the southern Maya civilisation began to disintegrate, the north enjoyed relative prosperity, with the rise of a number of thriving urban centres. These included one of the greatest of all Maya cities, Chichen Itza (one of the world’s “New Seven Wonders”). This northern resurgence flies against the drought theory of the Maya’s demise: if the south was permanently crippled by the climate shift, critics argue, then why wasn’t the north?
Researchers have proposed various explanations for this north-south discrepancy, but so far no one theory has won out. Recently, however, a new discovery has gone some way towards resolving this enduring paradox.
Chichen Itza was one of the greatest Mayan cities (Credit: AGF Srl /Alamy)
Chichen Itza was one of the greatest Mayan cities (Credit: AGF Srl/Alamy)
Maya archaeologists find dating difficult. Almost none of the Maya’s written records, which once numbered in the thousands, survived past colonial times (on the order of Catholic priests, the Spanish burned Maya books wholesale - only four are now known to exist). Instead, to determine the times that ancient Maya cities thrived, researchers rely on calendar inscriptions on stone monuments, stylistic analysis of the Maya’s ornate ceramics, and radiocarbon dates from organic materials.
Evidently the north didn’t come through these droughts unscathed after all
Earlier studies had already determined the approximate ages of the main urban centres in the northern Maya civilisation; it was these that had revealed that the north had endured the 9th Century droughts. However until recently this haul of data had never been gathered together in a single study. Doing so is important, because it allows the northern Maya region to be viewed as a whole, helping researchers to identify overarching trends in its rise and fall.
Now, in a study published in December, archaeologists from the US and the UK have brought together for the first time all of the calculated ages for urban centres in the northern Maya lands. These comprise about 200 dates from sites across the Yucatan peninsula, half obtained from stone calendar inscriptions and half from radiocarbon dating. The researchers could then construct a broad picture of what times the northern Maya cities had been active, and the times when they each might have fallen into decline.
What the team found significantly changes our understanding of when, and perhaps even how the Maya civilisation met its end. Contrary to previous belief, the north had suffered a decline during a time of drought - in fact, it had suffered two of them.
Calendar inscriptions declined in times of drought (Credit:  Image Source/Alamy)
The number of stone calendar inscriptions declined in times of drought (Credit: Image Source/Alamy)
 
There was a 70% decline in stone calendar inscriptions in the second half of the 9th Century. This same pattern of decline is also echoed in radiocarbon dates across the northern Maya region, which indicate that wooden construction also dwindled during the same time period. Importantly, this is the time that the droughts are believed to have caused the collapse of the Maya civilisation in the south – evidently the north didn’t come through these droughts unscathed after all.
The north certainly fared better than the south, but the region nevertheless suffered a significant decline  
The researchers believe that this waning of creative activity shows that political and societal collapse was underway in the north. The north certainly fared better than the south during the 9th Century, but these new findings suggest that the region nevertheless suffered a significant decline. This northern decline had previously escaped detection mostly due to the subtle nature of the evidence: a decline in construction, even one as large as this, is hard to spot without the comprehensive, region-wide analysis provided by the new study.
The northern decline of the 9th Century is an intriguing new detail in the Maya’s story, but it doesn’t fundamentally alter it - after all, we already knew that the northern Maya had survived past the 9th Century droughts (Chichen Itza and other centres thrived until well into the 10th Century).
But the second decline the team identified does change our understanding of the Maya’s story. After a short recovery during the 10th Century (which, interestingly, was coincident with an increase in rainfall), the researchers noticed another slump in construction at numerous sites across the northern Maya territory: stone carving and other building activity seems to have fallen by almost half between AD1000 and 1075. What’s more, just like the crisis 200 years earlier, the researchers discovered that this 11th Century Maya decline also took place against a backdrop of severe drought.
And not just any drought. The ones in the 9th Century had certainly been severe. But the 11th Century brought the worst drought that the region had seen for fully 2,000 years - a “megadrought”.
Severe drought affected the Maya (Credit: YAY Media AS/Alamy)
The 11th Century Maya decline occurred during a period of severe drought (Credit: YAY Media AS/Alamy)
After a short recovery there was another slump in construction in the north – against a backdrop of severe drought. Climate records show that rainfall diminished dramatically for the best part of a century, between around AD1020 and 1100 - a snug fit with the archaeologically derived dates for the collapse of the northern Maya. One correlation doesn’t mean much on its own. But find two, and even sceptics might start to whisper “causation”.
After this second wave of droughts there was to be no real recovery for the Maya
The 11th Century megadrought had been implicated in the fall of the northern Maya before, but the dating techniques used had given ambiguous ages, making it hard to tell if the timings of the two events really did overlap. The comprehensive analysis published in the December study lets us say with much greater certainty that climate change was contemporaneous with not one, but two devastating periods of Maya decline. 
If the first wave of droughts had finished off the Maya in the south, it looks like the second wave may have brought on their demise in the north. 
After this second wave of droughts there was to be no real recovery for the Maya. Chichen Itza and most of the other important centres in the north would never rise again. There would be small but noteworthy exceptions - such as the northern city of Mayapan which flourished from the 13th to 15th centuries - but these would never rival the size and complexity of the Classic Maya cities. In many ways, the 11th Century was the Maya’s last gasp.
With these findings, it looks even more likely that climate change played a significant role in the Maya’s downfall. But how?
The Maya were heavily dependent on crops (Credit: Robertharding/Alamy)
Most archaeological explanations for the collapse involve agriculture. The Maya, like all large civilisations, were heavily dependent on crops for their economic might - and of course to sustain their vast workforce. The simplest explanation for the Maya’s fall is that year-upon-year of low crop yields, brought on by the droughts, may have gradually diminished the Maya’s political influence, eventually leading to full-on societal disintegration.
Year-upon-year of low crop yields, brought on by the droughts, may have gradually diminished the Maya’s political influence
But even advocates of the drought hypothesis admit that the picture is bound to be more nuanced than that.
“We know that there was already increased warfare and socio-political instability throughout the Maya area prior to the 9th Century droughts,” says Julie Hoggarth at Baylor University in Waco, Texas, who co-led December’s climate analysis.
Inter-city conflict is a pretty good way to break up a civilisation too; it’s possible that the Maya just fought themselves apart. But that still leaves the question of the droughts, and those well fitting dates. Perhaps, then, it was a mixture of the two. As food stocks shrank during the dry decades, competition for resources would probably have become even more intense, perhaps eventually reaching a tipping point which caused the ancient Maya civilisation to fracture irreparably.
It's possible that the Maya just fought themselves apart (Credit: JORDI CAMÍ/Alamy)
It's possible that the Maya just fought themselves apart (Credit: JORDI CAMÍ/Alamy)
But there’s at least one other explanation that doesn’t require any warfare. It may not have been the Maya’s dark side that doomed them, but their talents. Because, while the Maya were famously great craftsmen, but they were also environmental sculptors.
To grow enough food to feed their millions, the Maya dug huge systems of canals, sometimes hundreds of miles across, which allowed them to drain and elevate the infertile wetlands which cover much of the Maya heartland, producing new arable land (some archaeologists call these “floating gardens”). The Maya also cleared huge tracts of forest, both for agriculture and to make room for their cities.
Deforestation to clear land for agriculture might have exacerbated localised drying effects
Some scholars think that the Maya’s skilled manipulation of their environment could have had a hand in their eventual collapse, by somehow worsening the impacts of natural climate change. For example, some scholars think that deforestation to clear land for agriculture might have exacerbated localised drying effects, leading to more significant agricultural losses during drought.
A more indirect consequence of their agricultural prowess might simply have been that it allowed the population to grow too large, which might have increased their vulnerability to an extended food shortage, and therefore reduced their resistance to a drier climate. 
(Credit: Age fotostock/Alamy)
Mesoamerica’s famous civilisation mysteriously fell about 1,000 years ago (Credit: Age fotostock/Alamy)
Whatever the reason – or reasons – for the Maya’s collapse, we do know something about the fate of the people who were left to face its aftermath. Starting around AD1050, the Maya took to the road. They abandoned the inland regions where their ancestors had thrived, and made their way in droves towards the Caribbean coast, or to other sources of water, such as the lakes and sinkholes which occasionally punctuate the dense green of the Maya’s former territory. 
The exodus of the Maya people may have been motivated by hunger. If the crops had indeed failed following the 9th and 11th Century droughts, relocating nearer water might have made sense, either to access seafood or to take advantage of the wetter land near the sea. Whatever the reason, moisture was clearly on their minds.
But then again, that had always been the case. One of the duties of a Maya ruler was to commune with the gods to ensure a wet year and good harvests. At sites across the Maya world, archaeologists have dredged up human bones from the bottom of lakes and sinkholes - thought to be doorways to the underworld: grim evidence that the people resorted to sacrifice to appease their deities. When the rains were good, and the civilisation blossomed, it must have seemed like their prayers were being answered. 

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วันจันทร์ที่ 15 กุมภาพันธ์ พ.ศ. 2559

John Paul letters reveal 'intense' friendship with woman


  • rom the sectio
Outside camping tent in Poland in the summer of 1978Image copyrightPhotograph provided by Bill and Jadwiga Smith
Image captionCardinal Wojtyla and Anna-Teresa Tymieniecka on a camping trip in 1978
Hundreds of letters and photographs that tell the story of Pope John Paul II's close relationship with a married woman, which lasted more than 30 years, have been shown to the BBC.
The letters to Polish-born American philosopher Anna-Teresa Tymieniecka had been kept away from public view in the National Library of Poland for years.
The documents reveal a rarely seen side of the pontiff, who died in 2005.
There is no suggestion the Pope broke his vow of celibacy.
The friendship began in 1973 when Ms Tymieniecka contacted the future Pope, Cardinal Karol Wojtyla, then Archbishop of Krakow, about a book on philosophy that he had written.
The then 50-year-old travelled from the US to Poland to discuss the work.
Anna-Teresa Tymieniecka in 1973Image copyrightPhotograph provided by Bill and Jadwiga Smith
Image captionAnna-Teresa Tymieniecka at the time she met Cardinal Wojtyla
Shortly afterwards, the pair began to correspond. At first the cardinal's letters were formal, but as their friendship grew, they become more intimate.
The pair decided to work on an expanded version of the cardinal's book, The Acting Person. They met many times - sometimes with his secretary present, sometimes alone - and corresponded frequently.
In 1974, he wrote that he was re-reading four of Ms Tymieniecka's letters written in one month because they were "so meaningful and deeply personal".
Photographs which have never been seen before by the public reveal Karol Wojtyla at his most relaxed. He invited Ms Tymieniecka to join him on country walks and skiing holidays - she even joined him on a group camping trip. The pictures also show her visiting him at the Vatican.
"Here is one of the handful of transcendentally great figures in public life in the 20th Century, the head of the Catholic Church, in an intense relationship with an attractive woman," says Eamon Duffy, Professor of the History of Christianity at Cambridge University.



In 1976, Cardinal Wojtyla attended a Catholic conference in the US. Ms Tymieniecka invited him to stay with her family at their country home in New England.
She appeared to have revealed intense feelings for him because his letters immediately afterwards suggest a man struggling to make sense of their friendship in Christian terms.
In one, dated September 1976, he writes: "My dear Teresa, I have received all three letters. You write about being torn apart, but I could find no answer to these words."
He describes her as a "gift from God".
The BBC has not seen any of Ms Tymieniecka's letters. It is believed copies of them were included in the archive that was sold to the Polish National Library by Ms Tymieniecka in 2008, six years before she died. But they were not with the Pope's letters when the BBC was shown them. The National Library of Poland has not confirmed that they have Ms Tymieniecka's letters.
Marsha Malinowski, a rare manuscripts dealer who negotiated the sale of the letters, says she believes Ms Tymieniecka fell in love with Cardinal Wojtyla in the early days of their relationship. "I think that it's completely reflected in the correspondence," she told the BBC.
The letters reveal that Cardinal Wojtyla gave Ms Tymieniecka one of his most treasured possessions, an item known as a scapular - a small devotional necklace worn around the shoulders.
The scapular given to Ms Tymieniecka
Image captionThe scapular given to Ms Tymieniecka
In a letter dated 10 September 1976 he wrote: "Already last year I was looking for an answer to these words, 'I belong to you', and finally, before leaving Poland, I found a way - a scapular. The dimension in which I accept and feel you everywhere in all kinds of situations, when you are close, and when you are far away."
After becoming Pope he wrote: "I am writing after the event, so that the correspondence between us should continue. I promise I will remember everything at this new stage of my journey."
Cardinal Wojtyla had a number of female friends, including Wanda Poltawska, a psychiatrist with whom he also corresponded for decades.
But his letters to Ms Tymieniecka are at times more intensely emotional, sometimes wrestling with the meaning of their relationship.
Pope John Paul II died in 2005, after an almost 27-year reign. In 2014 he was declared a saint.
The Pope at the Vatican with Anna-Teresa TymienieckaImage copyrightPhotograph provided by Bill and Jadwiga Smith
Image captionThe Pope at the Vatican with Anna-Teresa Tymieniecka
The process of saint-making is usually long and very costly, but John Paul II was fast-tracked to sainthood in just nine years.
Normally the Vatican asks to see all public and private writings when considering a candidate for sainthood, but the BBC has not been able to confirm whether the letters were seen.
The Congregation for the Causes of Saints said it is up to individual Catholics to decide whether to send in documents.
"All our duties were done," it told the BBC in a statement. "All private documents, sent by faithful as a response to the edict, and documents found in important archives were studied."
The National Library of Poland disputes that this was a unique relationship. It says it was one of many warm friendships the Pope enjoyed throughout his life.

วันเสาร์ที่ 13 กุมภาพันธ์ พ.ศ. 2559


Gravitational Waves Were the Worst-Kept Secret in Science

Two merging black holes produced gravitational waves that swept through Earth, exciting not only scientists but a frenzied rumor mill. (SXS Collaboration)
Two merging black holes produced gravitational waves that swept through Earth, exciting not only scientists but a frenzied rumor mill. (SXS Collaboration)
Now that we know the big news—scientists have observed gravitational waves, produced by a pair of merging black holes—let’s revisit the clustercuss of a quagmire in which it was announced. While the scientists kept quiet about their discovery, it quickly became one of worst-kept secrets in the scientific world.
That’s because rumor-hungry scientists and journalists refused to let the scientists looking for gravitational waves, the LIGO team, drive its own train. Given the rigor with which a breakthrough of this magnitude is evaluated, not only do these premature disclosures not serve readers, they’re irresponsible, arguably unprofessional, and potentially harmful.
It started way back in September, when physicist Lawrence Krauss sent out this tweet:
Krauss then doubled down on that rumor in mid-January, tweeting that his earlier statement had been confirmed. The disclosure primed a rumor mill that churned nearly nonstop for weeks, adding unnecessary chatter to a universe that’s already overwhelmed with sound. For a month, blog after blog after news story after tweet reported an evolving set of rumors about how, where, and what the LIGO team would announce. Earlier this week, when an upcoming LIGO press conference was announced, coverage dialed up to 11 — but at least there was something tangible to hang speculation on.
As a science journalist, I found the spectacle enormously frustrating to observe, and the coverage seemed eerily ignorant of the disaster that unfolded two years ago when a different team claimed to have detected a different species of gravitational waves.
In 2014, the team running the BICEP2 experiment at the South Pole announced the discovery of primordial gravitational waves, or imprints left over from a rapid period of cosmic expansion just after the Big Bang. But the BICEP2 team hadn’t yet submitted their results to a peer-reviewed journal; in the aftermath of the announcement, it became clear that the team’s analysis contained serious flaws, and when scientists examined the data further, the detection disappeared.
Perhaps learning from the mistakes of others, LIGO scientists have said they wouldn’t make an announcement before their paper passed peer review and was on its way to publication in an academic journal. Given that the team didn’t even submit its paper to Physical Review Letters until January 21, at the time Krauss was tweeting and reporters were writing, nobody was ready to announce anything. Nobody was going to confirm those swirling rumors, no matter how good the information we had was.
Suppose rumors of the LIGO team’s discovery were premature, and the signal fizzled beneath the weight of peer review or the scientific process. The damage – to the LIGO team, to the field of gravitational wave astronomy (especially given both historical and recent high-profile SNAFUS), to sources, to your own credibility – that could have been done by spreading these rumors vastly outweighed what little could be gained from a premature disclosure. The LIGO team would have appeared to fail at something it had never publicly promised to deliver at this point.
Conversely, to state the obvious, except for the potential loss of clicks on your page, there is no harm in waiting for the LIGO team to make their announcement.
Now, I have to wonder, is there value in reporting a rumor you can’t confirm? It’s reckless journalism. Sure, entertainment and political reporters do this kind of thing all the time, but that doesn’t make it right. How does it benefit your readers? Maybe, if you write for a publication that’s geared toward scientists, there’s merit in letting them know what their peers may or may not be up to, in lifting the curtain and taking a glimpse behind the scenes. But a general audience? I’d argue there isn’t much of a reason to jump into the fray, and many reasons to stay out of it.
With a discovery this significant, it is irresponsible to abandon professional decorum and get swept up in excitement. That’s not our job as journalists, and I’m quite sure it’s not great behavior for scientists, either. I’m not arguing that we all need to abide by a flawed and archaic embargo system, where we all agree not to publish something until an agreed-upon time, or that we need to align ourselves with scientific interests rather than doing our jobs of being objective and holding truth to power. I’m just suggesting that we hold ourselves and our motivations to higher standards and consider our decisions in the context of the audience we serve and the potential consequences.

วันจันทร์ที่ 8 กุมภาพันธ์ พ.ศ. 2559

The lost giants that prowled the Australian wilderness

If you think modern Australian animals are scary, spare a thought for the country's earliest human inhabitants. They had to contend with huge kangaroos and 5-metre carnivorous lizards
Australia's wildlife is unique. The vast majority of the animals that live there are not found anywhere else – and things were no different 1 million years ago during the Pleistocene: the age of the super-sized mammal.
Before humanity became Earth's undisputed superpower, giant beasts of all shapes and sizes dominated every continent, from the mammoths of Siberia to the ground sloths of South America.
In typical Antipodean fashion, the Pleistocene mammals of Australia were different. On most of the continents it is placental mammals that dominate, but Australia was (and still is) the heartland of the marsupials.
Australia's Pleistocene marsupials were closely related to the pouched, fluffy creatures that still hop and scurry around the outback today. But some of them could grow to the size of small cars, or possessed teeth longer than knife blades.
These monster marsupials were not the only giants. Their numbers were swelled by 5m-long lizards, half-tonne birds and giant, dinosaur-like tortoises. The result was a truly nightmarish biological assemblage.
None of these animals survive today – although exactly why that's the case is a mystery. Humans, with their advanced hunting techniques and use of fire to modify the landscape, may have played a central role in the megafauna's disappearance, but this idea is still a matter of heated debate.
Even if we cannot be sure that the arrival of Australian Aboriginals on the continent had catastrophic effects on its native animals, it seems that the animals had a rather spiritual effect on the humans. The Aboriginal mythological "Dreamtime" includes a cast of monstrous creatures, many of which bear a close resemblance to some of the real-life monsters that once stalked Australia's plains. Are the myths based in fact? Perhaps: after all, these creatures are far stranger than anything dreamed up by humans.
Diprotodon octatum: largest marsupial (Credit: Stocktrek Images Inc/Alamy Stock Photo)
Diprotodon octatum was the largest ever marsupial (Credit: Stocktrek Images Inc/Alamy Stock Photo)
Diprotodon
Weighing two tonnes, the Diprotodon comfortably holds the title of largest marsupial ever. In size and appearance it looked superficially like a modern rhinoceros, but the Diprotodonseems to have had a social lifestyle more like that of an elephant, another mammal with which it shares anatomical similarities.
What the Diprotodon most resembles, however, is exactly what it is: an enormous wombat.
Early European colonists searched feverishly for a living specimen of this fabulous creature
Like its modern counterpart,Diprotodon possessed powerful, clawed feet that were most likely used to tear at vegetation and dig for roots. Unlike modern wombats,Diprotodon would have had no need to extend its digging operations further underground for shelter, as only the hardiest of predators would have targeted it.
Hundreds of Diprotodon skeletons have been unearthed in Lake Callabonna, a dry salt lake in which multiple family groups seemingly wandered in search of food during the dry season, only to fall through the brittle surface and become trapped in mud.
The bunyip, a lake monster that drags unsuspecting passers-by into its watery lair, may be a cultural Aboriginal memory from the days when many Diprotodon wandered the swamps of Australia. This popular idea was first suggested in the mid-19th Century.
Certainly there have been incidences of Aboriginal Australians identifying Diprotodon bones as belonging to bunyips. Early European colonists searched feverishly for a living specimen of this fabulous creature – but without success.
Procoptodon (Credit: Natural History Museum, London/Science Photo Library)
Giant prehistoric kangaroos (Procoptodon) (Credit: Natural History Museum, London/Science Photo Library)
Giant short-faced kangaroo
Procoptodon goliah, the largest of the so-called short-faced kangaroos, is also the largest kangaroo known to science. Standing 2m tall and weighing almost three times as much as a red kangaroo, these hulking marsupials were a walking contradiction – a kangaroo that could not hop.
They possessed "short faces" with eyes that were almost forward-facing, like our own
Analysis of extinct and extant species has suggested that the Achilles tendons of these monster 'roos would not have withstood the impact of the hopping motion – unlike the kangaroos we know and love today.
Instead, they probably shuffled around on large, one-toed feet, in a bipedal fashion that is very unusual in the mammal world – even though it is the way we humans get around, of course.
And just like humans, these kangaroos possessed a key adaptation for such a lifestyle: a well-developed set of buttocks. Such musculature is absolutely key if an animal is to balance while lifting one leg at a time off the ground.
Intriguingly, their walking style is not the only thing connecting these kangaroos with humans. As their name suggests, they possessed "short faces" with eyes that were almost forward-facing, like our own. This, combined with the kangaroos' primate-like teeth, gave them uncannily simian features, although it is fair to say any confusion with modern apes or indeed humans is unlikely.
The skull of a marsupial lion (Credit: National Geographic Creative/Alamy Stock Photo)
The skull of a marsupial lion (Credit: National Geographic Creative/Alamy Stock Photo)
Marsupial lion
With all of these big juicy slabs of marsupial meat wandering around, it is little wonder that enormous predators evolved.
Elsewhere in the world this niche would have been occupied by dogs or big cats, but not in Australia. Enter top Pleistocene predator Thylacoleo carnifex to banish any remaining thoughts that marsupials are cute and cuddly.
The marsupial lion had the most powerful bite force for its size of any known mammal species
The 1m-long marsupial lion was not a true lion, of course. This creature was in fact closely related to theDiprotodon, but at some point in its evolutionary history, it took a drastically different course from its herbivorous cousin.
In fact, the marsupial lion is a true testament to the power of evolution to "make do" with the raw materials at its disposal.
The group that Diprotodon belongs to is not blessed with scary canines of the type seen in most predatory mammals. What they do have, however, is large, forward facing incisors that allow them to slice through tough plant matter. In the marsupial lion, these incisors developed into huge, pointed weapons that were perfect for taking down large prey.
Thylacoleo also possessed oversized premolars with slicing edges that would have allowed it to butcher a carcass with ease.
In fact, simulations have indicated the marsupial lion had the most powerful bite force for its size of any known mammal species, living or dead. It might have had unpromising evolutionary roots for a predator, but this beast really was a force to be reckoned with in the ancient outback.
A pair of Palorchestes (Credit: Natural History Museum, London/Science Photo Library)
A pair of Palorchestes (Credit: Natural History Museum, London/Science Photo Library)
Palorchestes
Initially characterised as another giant kangaroo species, thePalorchestes genus has undergone several major makeovers since its initial description in 1873. As more fragments of skeleton have emerged, new theories have been profferedby palaeontologists as to what these creatures looked like.
Deep lower jaws would have been the perfect anchor for a long, prehensile tongue similar to that of the giraffe, while a recessed nasal cavity suggested the presence of a small trunk, which has given rise to the common depiction of Palorchestesas a group of marsupial tapirs – some of which grew to 2.5m in length.
But they are also clearly close relatives of the Diprotodon, based on anatomical similarities such as powerful claws. This creates the impression that Palorchestes could be sizeable, rotund creatures something like trunked ground sloths.
Intriguingly, Aboriginal rock art dating from the time thatPalorchestes was still alive lends weight to this depiction. Paintings of creatures that look remarkably like the scientific reconstruction of Palorchestes suggest not only that those reconstructions are accurate, but also that these animals bore some significance to the early settlers of Australia.
This is not the first time insights have been gained from studies of ancient Aboriginal rock art. Paintings of animals resembling marsupial lions indicate that, like modern tigers, they had striped markings, lending support to the theory that they too were camouflaged ambush predators.
Artist's impression of Dromornis stirtoni (Credit: Jaime Chirinos/Science Photo Library)
Artist's impression of Dromornis stirtoni, with its chicks (Credit: Jaime Chirinos/Science Photo Library)
Dromornis
Not all of the Australian megafauna were marsupials. The continent was also once home to large birds, some growing to 3m tall. Enter Dromornis stirtoni, a bird that looked superficially like an ostrich or an emu – but that was actually more closely related to ducks and geese.
Both Dromornis and Bullockornis disappeared from the continent long before humans arrived
This has earned one related species, the 2.5m-tall Bullockornis planei, the fanciful nickname "Demon Duck of Doom".
Whether that nickname is appropriate or not is unclear. These birds possessed enormous beaks that would be just as capable of crushing seed pods as skulls. On the one hand, the lack of predatory hooks on their bills or talons on their feet suggest a herbivorous lifestyle, but on the other hand the sheer power and offensive capability of their heads hints they showed at least some degree of predatory behaviour.
Both Dromornis and Bullockornis disappeared from the continent long before humans arrived. But some of their relatives – including the 2m-tall Genyornis – were very much a part of the Pleistocene megafauna that greeted the first Australians. They, too, were captured for posterity in Aboriginal rock art.
As the eggshells of these giant birds are surprisingly well preserved across Australia's fossil beds, they have served as a useful proxy for extinction dates in different regions. These shells have helped to implicate humans in the extinction of the Australian megafauna.
Varanus priscus was a huge lizard (Credit: Stocktrek Images Inc/Alamy Stock Photo)
Varanus priscus was the largest land-living lizard in history (Credit: Stocktrek Images Inc/Alamy Stock Photo)
Megalania
Another record breaker, this time a world champion; Varanus priscus, commonly known by its antiquated genus nameMegalania – was the largest terrestrial lizard the world has ever known.
Megalania was a goanna lizard, a relative of today's infamous Komodo dragon, and conservative estimates have predicted that it was at least 5.5m long.
This would make Megalania the largest venomous animal ever to have lived
Early descriptions of Megalaniafossils by the likes of palaeontology superstar Sir Richard Owen described a truly monstrous creature, more like 7m in length, which sat unchallenged at the top of the food chain. As understanding of ancient Australian ecosystems has increased, and the importance of mammalian predators such as the marsupial lion appreciated more fully, Megalania's status has shrunk, along with its projected size.
However, even at "just" 5.5m, this giant lizard would have been one formidable predator.
Like its relative, the Komodo dragon, Megalania was armed with a lethal arsenal of curved teeth. A 2009 investigation into the poorly understood predatory ecology of Komodo dragons, which also incorporated some comparative anatomy ofMegalania teeth, indicated that the dragons possess a venom delivery system. By association, Megalania may well have done so too.
If so, this would make Megalania the largest venomous animal ever to have lived.
Meiolania platyceps was a monster tortoise (Credit: Smokeybjb, CC by 3.0)
Meiolania platyceps was a monster tortoise (Credit: Smokeybjb, CC by 3.0)
Meiolania
Like Megalania and other pumped-up reptiles from Pleistocene (including the 9m-long Bluff Downs Giant Python), Meiolania platyceps was certainly big enough, at 2.5m, to hold its own in the company of Australia's giant marsupials.
Crafty humans were not intimidated by these walking tortoise fortresses
This massive tortoise not only dwarfed any modern specimens, it also possessed a pair of impressive horns on top of its head. Such devilish appendages would have prevented these reptiles from withdrawing their heads into their shells, as most modern tortoises do when faced with a threat.
However it's fair to assume that Meiolania platyceps was not one to run away from a fight.
In addition to a heavily armoured front end and a large, domed shell, these tortoises possessed spiked tails that would have made potential aggressors think twice before taking a bite out of them. The combination of features means Meiolaniaplatyceps superficially resembles a group of armoured dinosaurs called the ankylosaurs, which could hold their own against Tyrannosaurus.
Unfortunately, crafty humans were not intimidated by these walking tortoise fortresses. While the fate of Meiolania platyceps remains unknown, a clue is offered by some bones unearthed on the Pacific island of Vanuatu belonging to a close relative, M. damelipi.
Unlike their larger cousins, who went extinct during the Pleistocene, these tortoises survived well into the age of humans, only to be exterminated by a seafaring people called the Lapita around 2,000 years ago.
Remains of butchered leg bones found in rubbish pits give an indication as to the gastronomic fate that might also have befallen Australia's giant tortoises.
The last known thylacine (Thylacinus cynocephalus) (Credit: Dave Watts/naturepl.com)
The last known thylacine (Thylacinus cynocephalus) (Credit: Dave Watts/naturepl.com)
Tasmanian Tiger
The Thylacine serves as a cautionary tale for anyone who doubts humanity's ability to annihilate species. Unlike most of Australia's megafauna, which went extinct tens of thousands of years ago, these wolf-like marsupials survived on the island of Tasmania well into the 20th Century; long enough, even, forfilm footage of them in captivity to exist.
It seems unlikely that thylacines will ever rise from the ashes
Though not as "mega" as most megafauna, thylacines were powerful apex predators capable of hunting other sizeable marsupials such as kangaroos and wallabies. This, ultimately, was their downfall, as European settlers in Tasmania inferred from their predatory appearance that they were responsible for attacks on sheep.
The local government placed a bounty of £1 per thylacine head, and this, combined with increased habitat degradation by humans and competition with settlers' dogs, led to total extinction by 1936.
Though unconfirmed sightings continue to this day, and Tasmania's landscape is both inaccessible and theoretically amenable to supporting such creatures, it seems unlikely that thylacines will ever rise from the ashes.
It is a reminder that, while we may lack scimitar-like teeth, crushing beaks or horned heads, it is humans that are the most lethal of all megafauna.

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