Tag Archives: South America

When Did the Human Epoch Begin?

It’s no secret that humans, in the short amount of time they’ve existed – a little less than 300,000 years in their present form, have had a sizable impact on the planet – well before the age of climate change widely believed to have begun with the Industrial Revolution. While the last two centuries have seen the human race advance to the point of being able to alter climates – processes that typically take thousands of years. For better or worse, we’ve influenced the evolution of countless species throughout the animal kingdom – from bacteria to mammals. We’ve championed vermin like the brown rat and cockroach, and driven countless other species of plants and animals to extinction.

So greatly have we changed the planet in our conquest, that now geologists have sought to label the age in which we live as the Anthropocene. The only point of controversy, however, is deciding when exactly the Anthropocene Era began. Was it with the Industrial Revolution – or did it happen much later – with the advent of nuclear weapons in the mid-20th century? Now, there is evidence to suspect that the roots run much deeper. Many now believe that the Age of Imperialism, the first permanent settlements in North and South America by Europeans, may have ushered in this new era, leaving a substantial impact on the planet that had never been seen before. The research was published in Nature this week.

When analyzing layers of rock, geologists use these layers as a chronology for our planet. Typically, these layers represent periods of millions of years, separated by specific instances of disaster that lie in the narrative of the rock – extreme episodes of volcanic eruptions, or meteor collisions that set forth extinction events – the most known being perhaps the Cretaceous-Paleocene event that happened 65 million years ago, when an asteroid near the Yucatan Peninsula wiped out the dinosaurs.

Currently, in geologist terms, we live in the Holocene Epoch – one that began some 12,000 years ago at the end of the last Ice Age, when sea levels began to rise. However, the overwhelming evidence of climate change – even some dating well before the Industrial Revolution – to Spanish conquistadors mining silver in Peru at the turn of the 17th century – has led many geologists to label the next era as one distinct from the Holocene, in which people have greatly altered the planet from the days when we were mere hunter-gatherers. All that’s left before an international committee of geologists weighs in on the decision, is to determine which event ushered in this new era.

According to Prof. Mark Maslin, from University College London, who co-wrote the paper: “We look for these golden spikes – a real point in time when you can show in a record when the whole Earth has changed. If you look back through the entire, wonderful geological timescale, we have defined almost every boundary in that way.”

Maslin and colleagues have pinpointed the start of the Anthropocene to 1610, when such a golden spike did occur. It was just over a century since the first Europeans arrived, only three years after the establishment of the Jamestown colony in present day Virginia.

Co-author Dr Simon Lewis, also of UCL, added: “The rapid global trade after that time moved species around.

“Maize from Central America was grown in southern Europe and Africa and China. Potatoes from South America were grown in the UK, and all the way through Europe to China. Species went the other way: wheat came to North America and sugar came to South America – a real mixing of species around the world.

“We saw these species jump continents, which is a geologically unprecedented impact, setting Earth off on a new evolutionary trajectory.”

The researchers discovered ancient pollen in sediments on American soil, which show evidence of when new crops were introduced. But that’s far from the entire record. Another golden spike is in the remnants of deadly epidemics, such as smallpox, carried from European ships into the New World.

“Around 50 million people (in the Americas) died, and most of those people were farmers,” Dr. Lewis said on the BBC World Service’s Science in Action news program.

“And this farmland grew back to the original vegetation – tropical forest, dry forest or savannah. And about half the dry weight of a tree is carbon, so all that growing vegetation removed enough carbon from the atmosphere to see a pronounced dip in the global atmospheric carbon dioxide concentration that can be seen in ice core records.

“It provides an exact marker of the Anthropocene at 1610, the lowest point of CO2 in the ice-core record at that time.”

Yet, the debate is still far from over. Atomic bomb weapons testing following the Second World War has also left a pretty clear mark that humanity was here. Alternatively, Lewis and Maslin have proposed the year 1964 as the start of the Anthropocene, the year in which nuclear testing was banned across the globe. While these tests took place, however, there was a sharp buildup in radioactive carbon throughout the atmosphere. A sharp drop followed once they stopped.

Although this was a pronounced signal, this radioactivity did not lead directly to any global changes at the time.

Maslin attributes the extreme changes since then to modernization and a sharp increase in population: “In the mid-1960s, there is a huge change in everything around the planet, which is called the ‘great acceleration’ – with the population increasing by 2% per year, unprecedented changes in agriculture and food production – but the marker doesn’t link to that in any shape or form.”

Dr. Jan Zalasiewicz, from the University of Leicester, who chairs the Anthropocene Working Group and was not involved in the new study, said that this new paper offered “intriguing ideas” about where the researchers should begin to look when it comes to labeling the Anthropocene Era.

“The working group will certainly be discussing them,” he said to BBC News.

“It adds positively to the overall debate on the Anthropocene, and to the growing number of suggestions about where it should start.

“The 1610 suggestion clearly reflects a historically important event, though it would need more evidence, I think, whether the criteria they suggest would work better than the multiple signals now known to be associated with the mid-20th century ‘great acceleration’.”

Wherever the mark may begin, the golden spikes are clearly in place – imminent that there is a geological record of humanity’s interaction with the Earth, yet another attribute that may set us apart from the species that preceded us.

James Sullivan
James Sullivan is the assistant editor of Brain World Magazine and a contributor to Truth Is Cool and OMNI Reboot. He can usually be found on TVTropes or RationalWiki when not exploiting life and science stories for another blog article.

When Gators Ruled The Earth: South America Was A Crocodilian Paradise Before the Amazon

You don’t have to travel far in Florida to see their iconic state reptile up close – Alligator missippiensis, the American Alligator. This apex predator has made such a successful comeback over just the last two decades. If you think finding one of them in your pool or at your door is bad news, consider yourself fortunate that you didn’t live in the South American jungles about 13 million years ago. Back then, these prehistoric beasts not only thrived in the American Southeast, but occupied a significant territory in what is now the western part of the Amazon River Basin. And they had competition, too. Peruvian paleontologists identified seven different species of crocodilians who called this region home. A great deal of diversity among each suggests that there might have even been more.

In the modern Amazon jungles, you never see more than three different types of crocodilians sharing territory – often alligators and their fairly close relatives the Central and South American caiman.

“It was a real crocodilian community,” said the study’s co-author, Rodolfo Salas-Gismondi of the Museum of Natural History in Lima, Peru. “To find seven species is just amazing.”

On the outskirts of Iquitos, Peru, Salas-Gismondi and his team stumbled across two large outcroppings of rock. Embedded in each was fossil evidence of seven different species who all co-existed in the same ecosystem. While the Amazon we know today is perhaps one of the most unique and delicate ecosystems in the world, it may have been preceded by ones that were a whole lot stranger. Salas-Gismondi suspects that such diversity among these monsters was due to the humidity and frequency of rainfall in the wetlands. 13 million years ago it was an immense swampland, offering limitless food for the crocodilians – another way to explain why some of them grew to massive proportions.

One of the prehistoric beasts that lived alongside the American Alligator and the South and Central American Caiman was Mourasuchus atopus, a behemoth that may have filtered water through its mouth to trap fish, in the way some modern birds do.

Another uncovered fossil was the already identified Purussaurus neivensis – a giant caiman the size of a stretch limousine and an apex hunter that fed off mammals and large turtles.

Perhaps most intriguing and most unlike any known living crocodilians today were three different animals that the researchers referred to as crushers, all of which were unknown to science until Salas-Gismondi published his work in the latest volume of Proceedings of the Royal Society B: Biological Sciences. The star of their paper was the creature Gnatusuchus, a name meaning “small-nosed crocodile.” Its skull was first found in a mud pile back in 2006, and was nearly destroyed by a motorboat propeller when the pilot hurried ashore to tie up his vessel.

“The thing was sitting there with the top of the skull and the eyeballs looking at us,” said one of the study’s co-authors John Flynn from the American Museum of Natural History in New York City. “It was just an incredible feeling, knowing immediately it was something so different.”

As intimidating as the name ‘crusher,’ may seem – you might think of them as the crocodilian version of Darwin’s finches – animals that adapted specifically to a diet of shellfish and mollusks which they would crush open with the use of their back teeth. A number of crushed clams have also been found in the fossil deposits.

“I didn’t really think of crocs as being clam-eaters before,” said vertebrate paleontologist David Schwimmer of Georgia’s Columbus State University, commenting on the latest research. “It’s not exactly ferocious, hunting down the giant killer clam. Just think of the image.”

While it was long suspected that the wetland’s apex predators were crocodilians of some sort, and the fossils shed valuable light about how this ecosystem may have worked, it is also an invaluable way to learn more about the diversity of crocodilians. The sixth type identified by the researchers as Caiman wannlangstoni, is believed to be one of the more recent ancestors of modern caimans.

So what happened to this forgotten link? The known crushers seem to be part of a very diverse branch of crocodilians, so how did they all disappear until now? The most likely answer is that the Amazon River itself was responsible. When it formed some 10.5 million years ago, it brought new currents of water flowing eastward into the Atlantic. When the sea levels dropped after the last Ice Ages, much of the swamplands were wiped out, along with the mollusks who specially adapted to it, killing off the crushers’ food supplies.

The Amazon also makes for poor preservation of fossils, as many minerals that are present in fossilization are recycled into the rainforest. The team was fairly fortunate to uncover these animals as well, since heavy vegetation alongside the river banks makes digging difficult.

James Sullivan
James Sullivan is the assistant editor of Brain World Magazine and a contributor to Truth Is Cool and OMNI Reboot. He can usually be found on TVTropes or RationalWiki when not exploiting life and science stories for another blog article.