Mammoth Extinction

The extinction of the Pleistocene megafauna is a heavily debated topic, was it over hunting by man or was it climate change? We now have the answer thanks to the University of Adelaide.

By analysing ancient DNA, using radiocarbon dating and other geologic analysis methods, the University of Adelaide has shown that short rapid warming events, known as interstadials, experienced during the past ice age at the end of the Pleistocene coincided with major extinction events even before man became dominant.

Professor Alan Cooper says that "abrupt warming had a profound impact on climate that caused marked shifts in global rainfall and vegetation patterns". It was therefore sudden warming not extreme cold that killed the Woolly Mammoths in Eurasia.

However, Professor Chris Turney believes that "man still played an important role in the disappearance of megafauna".

The culminating factors of rapid warming and the constant pursuit of man pushed the Mammoth's over the edge as they were already under extreme stress with a lack of tundra shrubs and grasses available as the ice retreated further north, this would have lowered reproduction success and limited the sizes of the herds as the food could not support the animals.

Let me know what you think of this, do you think the Mammoth's extinction was a result of the rapid warming of the climate or did early man hunt the Mammoths to the point of extinction?

http://www.sciencedaily.com/releases/2015/07/150723181113.htm?utm_source=feedburner&utm_medium=email&utm_campaign=Feed%3A+sciencedaily%2Ffossils_ruins%2Fpaleontology+%28Paleontology+News+--+ScienceDaily%29

Pleistocene Settlement at Creswell Crags

Creswell Crags in Derbyshire, UK, is a limestone gorge where settlements from the Pleistocene have been discovered. Although the caves were the primary shelters, there would have been man made huts made from animal skin and bones. But why did Creswell Crags prove to be an ideal site for prehistoric settlements? 

Creswell Crags Cave, Derbyshire, UK. Image Credit
hedgeduid.com

It is possible that early humans visited the Crags with the seasons in order to track herds of reindeer and horse. This was due to the herds being a vital source of food for early humans. They would have then returned to the South as the winter arrived. A stream ran nearby to the crags, water is a vital resource for humans and the herds of animals, providing a source of prey. Caves and rock overhangs would have sheltered early humans from the elements. But living in caves would have been dangerous as lions and bears also used caves as shelter. It is possible that the humans would have settled on top of the gorge's cliffs away from predators and the insects near the stream. The crags could have also been a meeting place, where information was shared and products traded. 

The settlements could be improved with simple amenities. Large rocks and post holes are found at the crags, this is evidence of primitive windbreaks being built from skins and wooden posts. Fire would have also been used for warmth and cooking. Fire also scares off animals. 

The caves are south facing, this allows for more sunlight to enter the caves. We find larger archaeological deposits in south facing caves because of this reason.

Mammoth cave painting, Roufignac, France. Image
credit mammoth.psu.edu

Many caves are found with early paintings. The purpose of cave paintings is not known. They are not believed to be decoration as the caves don’t show signs of long term habitation. Paintings are similar around the world they show mostly animals. Humans typically appear as hand stencils that were made by blowing pigment on a hand held on the wall. There are a number of theories behind the paintings; Henri Breuil interpreted the paintings as being hunting magic; meant to increase the number of animals present in the area to make hunting better. David Lewis-Williams developed the theory that suggests that the paintings were made by shamans. The shaman would enter the cave and enter a trance, then paint images of their visions.

The Fossilisation Process

When a land dwelling vertebrate dies its carcass is commonly disarticulated, this means its limbs are removed, often by predators and scavengers alike. Most of the decomposition of the organic material is done by bacteria that will feast on the rotting flesh that remains on the bones. Some bones are completely stripped clean of flesh and bleached in the sun. Others might be carried off or gnawed by rodents. Sometimes, disarticulated remains are trampled and scattered by herds of animals.


Sooner or later the bones are either destroyed or buried. If they aren’t digested their destruction can come from weathering; this is when the minerals in the bone begin to break down and the bones disintegrate. But the weathering can be stopped by rapid burial, it’s at this point fossils are formed. A body fossil is part of an organism that is buried and a trace fossil is an impression left behind in the ground by the organism.


Bone is made out of calcium-sodium hydroxyl apatite, this mineral weathers easily, this means that the mineral is no longer present once a bone becomes fossilised. This mineralogy can remain intact if the bone doe not come into contact with any fluids during its burial, something that is extremely rare.

It is possible to find tissues of extinct animals. Since bones are porous, the spaces once occupied by blood vessels and nerves fill up with minerals. This is called permineralisation.

Fossil of Archaeopteryx. Image credit Humboldt
Museum Fur Naturkunde Berlin

Pristine fossils can be found in geological lagerstatte, feathers of dinosaurs are known from these lagerstatte. Most famously the early bird Archaeopteryx is known from the Solnhofen lagerstatte in Germany.

Ammonite shells are originally made of aragonite, this is unstable so when fossilisation begins the aragonite becomes the more stable calcite. This calcite creates a cast of the shell and this is what we find today.

Woolly Mammoths and Woolly Rhinos have been discovered mummified in the permafrost in Siberia and Alaska. Soft tissue of a Tyrannosaurus Rex has even been found which allowed palaeontologists to see that the animal was female, within the fossil, red blood cells and connective tissues were found.

Natural mummies have been found in a variety of locations around the world; bog deposits or tar pits, deep inside caves, glacier ice and in the permafrost of Alaska and Siberia. A Woolly Rhinoceros was found mummified after it was covered in salty ground water that essentially pickled the carcass, preventing bacteria and microorganisms digesting the flesh by altering the pH of the environment which means that microorganisms cannot survive in these acidic conditions.

Mummified dinosaurs have been found, good examples of these mummies come from Brachylophosaurus and Edmontosaurus. Leonardo, the Brachylophosaurus that features in the palaeoart post, had skin impressions, muscle impressions that showed an excess of tissue around the neck, even parasites are found on Leonardo.


The permafrost is also effective as the low temperature prevents the bacteria from respiring by removing any moisture on the carcass through freezing. However, once the mummy is excavated the bacteria become active and decomposition begins.

Pleistocene Mammal Defences

Tusks:
A Mammoth could have used its tusks to defend itself like the modern day African Elephant. They would have been used to keep predators at bay; this would have made the young and oldest members of a herd particularly vulnerable as they wouldn’t have the strength or tusks to repel attack. Due to their curvature, the tusks were not suitable for stabbing at predators.

Mounted Woolly Mammoth tusk. Image credit
geoclassica.com

The tusks could also be used in the mating season. The adult males would battle each other to earn the right to breed. These animals may have also had to defend their territories from other herds. The size of the tusks may have been used as an intimidation tool, and physical contact being the final resort.


Communication:
Communication between modern day animals can be transferred onto extinct Pleistocene mammals. Mammoths may have communicated in a similar way to modern day elephants. They communicate over long distances using infrasound. This is inaudible to human hearing, which can detect sound between 20 and 20,000 hertz. However, over shorter distances they may have used louder bellows to warn of predators or to seem more threatening. This is a form of defence as the herd can escape or fight off the predator more efficiently than if it was attacked without warning.


Early humans had also developed speech in order to coordinate hunts. Without communication it is unlikely that hunts would have been so successful. It was 7 million years ago that hominids began to show signs of primitive speech, therefore by the time the Ice Age occurred, communication would have been more efficient, but not as evolved as present day speech.


Numbers:
Safety in numbers in the ice age would have been a major survival tactic. Even large animals such as Mammoths travelled in herds as a form of protection, this ensured that the young would reach an age where they are able to produce the next generation, the population would then thrive and either grow or remain constant.


Humans also survived in numbers. Cooperation between the tribe members would have ensured their survival. Food preparation, hunting and construction would have been shared between all members of the tribe, providing defence from the harsh conditions of the Ice Age as well as the predators that they share the land with.


Size:
Giant animals do not always need to be a part of a herd. The solitary Megatherium, could stand at a maximum height of six metres tall, it would have been intimidating to even a pack of Smilodon. At only 1.2 metres tall, Smilodon would have been dwarfed by Megatherium and therefore only the young and the weak would have been vulnerable. This is similar to the Mastodons and Mammoths.


Tools:
Humans developed the use of stone tools at the start of the Pleistocene, 2.5 million years ago. This included knives, spearheads and axes, all would have been used in everyday life to build shelters and hunt for food. This made humans more successful due to their coordination and range of tools.

Early humans harvesting meat, bone and skin from a mammoth. Image credit
humanorigins.si.edu

Humans also used animals as tools. The use of domesticated dogs was a key to the Homo sapiens outdoing their relatives the Neanderthals. The energy burden was now taken by the dog and not the human aiding in the taking down larger prey that essentially helped the humans to survive the harsh winters.