Megafauna Extinction Debate Gets Heated

What is the oldest debate in Australian science? Probably, the argument over what caused extinction of our Pleistocene megafauna – the diprotodons, giant kangaroos, marsupial tapirs, über-echidnas and other big and bizarre creatures that used to live here.

In 1877 the great English anatomist Sir Richard Owen suggested that these big animals had been driven extinct by “the hostile agency of man”. That is, hunting did it, in a process we now call overkill. Other people responded that climate change must have been the cause, and it was on.

A string of recent studies from a wide range of disciplines – geochronology, palaeoecology, palaeontology, and ecological modelling – have supported Owen’s opinion. But the argument continues. Why?

The main reason is that many Australian archaeologists reject overkill. They have looked for direct evidence that people killed megafauna, and they haven’t found it. No great piles of bones around ancient campsites; no diprotodon skeletons with spears stuck in their ribs; no arsenal of specialised weapons for bringing down large prey. Very few archaeological sites even have remains of people and megafauna in close association.

Some archaeologists conclude that megafauna-hunting just did not happen, or if it happened it was rare and insignificant. Often this conclusion is stated with a ringing confidence that dismisses all non-archaeological evidence for overkill.

But they have not asked a crucial question: if people did hunt megafauna to extinction, how much evidence of killing should we now be able to get from archaeological sites? A new paper by archaeologists Todd Surovell and Brigid Grund suggests the answer to that question is “very little or none”.

Surovell and Grund point out, first, that the period when archaeological evidence of killing of megafauna could have been formed is a small fraction of the total archaeological record of Australia. People arrived here between about 50,000 and 40,000 years ago. This is also the interval during which animals like diprotodon disappeared. A comparison of archaeological and fossil dates suggests humans and megafauna overlapped for only about 4,000 years continent-wide, and modelling suggests that if hunting caused extinction it would have been all over in less than 1,000 years in any place.

This means that no more than 8%, perhaps as little as 2%, of the Australian archaeological record covers the period of human-megafauna interaction. The “smoking gun” evidence of overkill should therefore be rare. Surovell and Grund show that the problem of finding such evidence is even worse than that, for two reasons.

First, when people first arrived their populations were necessarily small. Living sites therefore occurred at low density. As population size grew exponentially, site density increased. So, the very earliest sites must be far rarer than later ones.

But if overkill happened, populations of megafauna would have been going down as humans went up: as the density of sites was rising the proportion of them that could have contained evidence of megafauna kills was falling. Thus, sites with potential to preserve that evidence are actually a tiny proportion, perhaps much less than .01%, of the total archaeological record.

Second, material in archaeological sites degrades with time due to breakdown, weathering and scavenging of bone and removal by erosion. Old sites are eventually buried under sediments. The probability of discovering archaeological sites from the earliest occupation of Australia is intrinsically much lower than for later times, and most of the contents of those sites will have disappeared.

In fact, the very oldest archaeological sites in Australia typically contain only a few stone tools. They can tell us very little about interaction of the first Australians with any animals or plants, let alone reveal a picture of megafauna-killing.

Our fundamental task as scientists is to test hypotheses using evidence. To test the overkill hypothesis, we need a kind of evidence that would differ according to whether the hypothesis is true or false. Obviously, if overkill did not happen, evidence of megafauna-killing should be rare in the archaeological record. But, Surovell and Grund’s analysis makes it clear that if overkill happened, we should still expect evidence of killing to be rare. Therefore, failure to find such evidence does not amount to a test of the overkill hypothesis.

This does not mean that archaeological evidence of killing (or absence of such evidence) is useless in testing the overkill hypothesis. Surovell and Grund show it can be useful, by comparing the archaeological records of Australia, North America and New Zealand. All three places lost their megafaunas when people arrived, but this happened a very long time ago in Australia, and very recently (700 years ago) in New Zealand. North America is intermediate, with human arrival and extinction from 14,000 to 13,000 years ago.

Applying the same logic to all three cases, we predict that if overkill caused megafaunal extinction in each place the archaeological evidence of killing should be abundant in New Zealand, rare in North America, and vanishingly rare in Australia. That is exactly what we find.

There is so much evidence showing New Zealand’s moa were heavily hunted that nobody doubts overkill was the main cause of their extinction. In North America, there are undoubted kill sites for mammoths, mastodons and a few other species, but this evidence is far thinner than in New Zealand. Australian archaeology is yet to reveal any convincing evidence for megafauna-killing.

So, far from disproving overkill, the archaeological evidence from Australia is actually consistent with the overkill hypothesis.

Source: The Conversation, Christopher Johnson

Monday Ground Up: Hunter-Gatherers, Agriculture, and Global Warming

Hunter Gatherers: Brief Beginning

Hunter Gatherers are traditionally described as being highly nomadic individuals that traveled with very  few possessions in a marginal environment. Of course, the factors of the environment directly influenced the ability to be mobile. However, up until the Last Age, we can agree hunter gatherers were highly mobile.

Subsistence

Hunter gatherers were either practicing a specialized or generalized subsistence system. In case you don’t know the difference, specialized diets depended on one or a small number of resources, an example being corn or acorns. Generalized diets consisted of any resources available. Both approaches were efficient depending on resources readily available.

Formation of Complex Society

Hunter gather societies were egalitarian, with very limited authority or inequality, others were highly unequal. For instance, slavery was a historically-documented practice of some Northwest Coast and Alaskan hunter-gatherers.

Technologies of Hunter Gatherers

Hunter gatherers are responsible for some of the most widely known technologies, those being ceramics, fired pottery, and domesticated dogs and plants.

Domestication

Complex societies are directly affected by their agricultural subsistence systems, and highly complex societies always rely on domesticated plants and animals.

New World chronologies of domesticated species are poorly understood. The dating problems are due in part to the humid environments of Mesoamerica, where preservation is generally poor compared to the arid Levant. In addition, New World research is at least a generation “younger” than Old World research on domestication. Scholarly attention on plant domestication in the New World did not begin until the 1960s, compared with the 1940s in Southwest Asia.[1]

Domestication occurred all over the world, with no animals to speak of in the Americas, major reliance on domesticated animals and highly productive grasses in the Old World, and tubers, legumes, and fruits in much of the Americas.

Hunter Gathering During the Pleistocene

During the Pleistocene most of the world’s water was locked in ice. Globally, the climate was windier and dryer even nearest to the ice sheets. Hunter gatherers saw the first flora and fauna communities with the climatic shift.

Tropical forests like the Amazon or in Florida were once savannah environments, with spaced trees and shrubs in an open grassland. Even with the abundance of plant life, hunter gathers still preferred meat, as it provided them the most calories with the lest energy output.

Tropical forest hunter gathers had to work much harder than hunter gathers in other environments. Why? Although there was an abundance of plant resources in tropical forests, the plants were scattered, thus taking more time to collect what was needed.

Hunting was just as difficult. Tropical forests yielded smaller species of animals, and usually they were found in the trees due to the lack of ground cover. Hunter gatherers would exert much more energy traveling longer distances to procure plant and animal stuffs as opposed to hunter gatherers living on the savannah.

For example, the tropical Americas had an abundance of large terrestrial animals on the savannah. There’s no evidence for Pleistocene occupations of tropical forest environments.

Most archaeologists now believe that Pleistocene Americans were specialists who emphasized the hunting of terrestrial herd animals like horses, mammoths, and giant bison.  This is not to say that early Americans did not eat smaller mammals and plants, but that their lifeway and technology were focused on acquiring an abundant meat resource.[1]

Temperature Changes in the Pleistocene Tropics

Roughly 20,000 years ago global warming caused a shift in ocean currents, wind patterns, and rainfall. Forests started to expand as well as the plant resources already growing there. Large terrestrial animals started to die out. Hunter gatherers had to adjust their techniques of gathering resources. Specialized communities turned towards a more generalized subsistence system in order to survive.

Hunter-gatherers all over the world made this transition in the early Holocene; it is sometimes called the “broad-spectrum revolution.”

Horticulture to Agriculture

There’s been a debate about the transition to agriculture. Some assume agriculture happened at the exact same time all over the world and others hardly agree with this coincidence.

Archaeologically there was a disappearance of spear heads for hunting and an appearance of grinding technologies. Slash and burn like methods were used to clear forests to encourage the growth of fruits and tubers. Areas were manipulated to create islands of plant resources which hunter gathers returned to periodically to take advantage of the foods growing there.

Over time, individuals spent much more time near the garden plots and started to build semi and permanent settlements nearby. Wild foods started to grow and manipulated plants started to become more dependent on human intervention (ie squashes, sweet potatoes, and several kinds of fruit tree).

Hunter gatherers eventually decreased their mobility and started settling near rivers where they domesticated wild plants and fished. They practiced swidden agriculture; a temporary agricultural plot formed by cutting back and burning off vegetative cover.  Forest farmers’ fields could only be used for a few seasons before it was necessary to move to a new plot of land.

Almost all explanations for the shift from hunting-gathering to farming rely on climate change in some way, even Childe's Oasis Hypothesis.

The Oasis Theory (or Propinquity Theory) is a core concept in archaeology, referring to one of the main hypotheses about the origins of agriculture. First put forward by V.G. Childe in his 1928 book, "The Most Ancient Near-East", the oasis theory argues that the reason people starting living in settlements was because during a dry spell, the only livable place was near oases. .[4]

Agriculture developed in most temperate or sub-tropical parts of the world at the beginning of the Holocene, leading scholars to infer that climate change must have influenced the process. If people living in many environments, with access to very different resources all began domesticating plants at about the same time, was agriculture inevitable? [1][3]

Modern Hunter gatherers - Tribe – BBC

The Babongo of Gabon used to be known, derogatively, as pygmies. They're still treated as second-class citizens by their neighbours. But their expertise and knowledge of the forests is unique and their use of Iboga, a powerful hallucinogenic which lies at the heart of Babongo culture, makes them famous throughout Gabon.

Is global warming in some way responsible for the development of complex societies?

At the end of the late glacial conditions, as mentioned in the article Was Agriculture Impossible during the Pleistocene but Mandatory during the Holocene? A Climate Change Hypothesis., agriculture was impossible. [2]

However, following the conditions, plant intensive resource use was immediately utilized, leading me to believe an action forward approach was instigated by the hierarchical powers that be.

Since intense agriculture is a characteristic of complex societies, and agriculture is indeed sensitive to severe weather conditions, evolution like subsistence characteristic of complex systems could not take place during the Pleistocene. Consequently, in warmer and wetter conditions during the Holocene, evolution of agriculture was made easy, with due access to irrigation.

Population is set, due to the environment and societies with the abilities to obtain resources to acquire and maintain intensive subsistence strategies. Those having the key resources to outmaneuver the smaller societies with less intensive agricultural systems in place will out-compete the weaker of the two.

So was global warming in some way responsible? Evolution of subsistence systems in complex societies was relatively slow during the Pleistocene because of the impeding climatic conditions. However, glacial advances and retreats are not directly relevant to the origins of agriculture because population size grows faster and is able to adapt to cultural evolution. This is not to say global warming didn’t have any effect on complex societies.

Due to the extreme variations in climatic temperatures, evolution of plant use would have been extremely difficult. Consequently, hunting and farming communities would have been able to cope with catastrophic climate events. Complex systems seen within Pleistocene hunter gatherer societies didn’t rely on one resource and remained diversified in the event conservation had to take place.

Pleistocene America saw a rapid change in the environment when global warming altered rainfall amounts, wind, and ocean currents, thus leading to terrestrial animals dying out in masses. Americans were forced to adjust their lifestyles in order to survive. South Americans dealt with the climate change by becoming generalists, thus following all hunter gathers in what was called the “broad spectrum revolution”.

In an essence, although global warming did cause ocean levels to rise resulting in less arid land, complex societies turned to alternative methods of subsistence.

If global warming can cause such incredible changes in human social organization, will the present era of global warming bring about equally massive changes in human society?

As the human population continues to grow, so does the addition of carbon, causing the Earth’s climate to warm further. As we’ve seen from history, life has found a way and survived even the harshest of climatic changes. However, there have been some major re-distributions of species and extinctions associated with this climate shift as well.

Most of the world’s population is concentrated in coaster cities, as opposed to small nomadic tribes, and if sea levels were to rise even a few meters, the geographic landscape would be completely altered, and many cases, destroyed.

Years ago, if sea levels rose a few meters, it would have had very little effect. Consequently, such a sudden change in climate is hard to prepare for.

“Equally, it seems likely that as warming continues some areas may experience less precipitation leading to drought. With both rising seas and increasing drought, pressure for human migration could result on a large scale”. [3]

Also check out:

Evolution of Culture, Genetic Anthropology, and the “Eve Theory”

For decades, anthropologists have debated “The Eve Theory” – the theory that world cultures migrated and evolved from a single source – Eve, a reference to Adam and Eve mentioned in the Bible’s Book of Genesis as the first man and woman and the progenitors of all human life.

Sources

1. Dr. Sarah Barber. UCF. Anthropology of Complex Societies
2. Robert Boyd, Robert L. Bettinger, Peter J. Richerson
   2001 Was Agriculture Impossible during the Pleistocene but Mandatory during the Holocene? A Climate Change Hypothesis. American Antiquity Vol. 66, No. 3, 2001j, pp. 387-411. Society of American Archaeology.
3. "Climate change: evidence from the geological record ." The Geological Society. The Geological Society of London , November 2010. Web. 30 Jan 2011.
4. Oasis Theory
5. Picture Cro Magnon
6. Hunter Gatherer picture
7. Global Warming GIF

Monday Ground Up: Archaeological Discovery of Viking Artifacts Reveals Facts about Ancient Society

Guest Article By Maria Rainier

Scientists working in Norway’s Jotunheimen mountain range have been reaping the benefits of climate change, taking advantage of warmer conditions to make an exciting archaeological discovery whose implications may help to reconstruct the region’s ancient society.

With glaciers melting quickly enough to reveal layers of ice that have never been exposed before, it’s an archaeological opportunity almost too much to handle. Artifact collection in frozen areas is a delicate process which often requires finding an artifact within a few days of its emergence. The artifact must then be carefully removed, transported to a laboratory, and frozen to keep it from disintegrating. This is especially true of any type of fiber (clothing, rope, and thread), animal skins, feathers, or hair, while wood takes a few years to rot and is easier to manage for archaeologists.

The Viking artifacts being discovered in Norway are predominantly wooden hunting weapons, but archaeologists are still struggling to collect all specimens before they start to fall apart.

Artifacts from Viking Hunters

Archaeologists are quickly learning more about Viking reindeer hunters based on the tools they’re finding in the mountains. The most commonly discovered artifacts are part of an innovative scare tactic meant to drive reindeer toward hidden batteries of Viking archers. This scare tactic involved creating a barrier of wooden stakes spaced about 6 ½ feet apart. Each stake had a foot-long piece of wood tied to its tip so any gust of wind would cause the entire row of stakes to start “flapping,” scaring reindeer toward the waiting Viking hunters.

Most of these archaeological discoveries are incomplete, missing the thread which tied the moving pieces to the stakes, but scientists are hoping to find some intact as they increase their efforts. Bows and arrows and a leather shoe have also been found at the Jotunheimen sites.

Reconstructing Norway’s Ancient Society

According to Norse mythology, the Jotunheimen mountains were inhabited by the “Ice Giants,” also called Frost Giants or Jötunn (Jotunheimen means “home of the giants”). While they may have been tall in stature, these “giants” weren’t the superhuman entities of lore.

What archaeologists do know about them is that they had an organized society, a conclusion drawn from the way Vikings would have cooperated to create the stake barriers for reindeer hunting. Scientists hypothesize that they hunted in groups of 15 or 20, lying in wait together with their bows and arrows until the frightened reindeer ran within about 65 feet of them. This implies that Norway’s ancient society was characterized by hierarchy, as leadership would have been a necessary part of organizing and executing a collective hunting strategy. The prolific Jotunheimen sites are likely to offer more insights into this ancient society and scientists are working to make more meaningful archeological discoveries.


Bio: Maria Rainier is a freelance writer and blog junkie. She is currently a resident blogger at Online Degrees, researching areas of online colleges. In her spare time, she enjoys square-foot gardening, swimming, and avoiding her laptop.

Sources:

Photo: Marcin Szala, used with permission

Cooler Pacific Ocean Affected Medieval Europe, North America

Using cores of fossil coral from the Palmyra Atoll in the central Pacific Ocean, Burgman and a team used reconstructed sea surface temperatures from the period 1320 to 1462 to simulate medieval climate conditions with a state-of-the-art climate model. When the differences between medieval and modern climate simulations were compared with paleo-records like tree-rings and sediment cores from around the globe, the authors found remarkable agreement.