Megafauna and Environment of the Quaternary Time Period
By Melissa Baccus
Extinct animals from the Quaternary time period by Review of the Universe
The Quaternary time period is from 1.8 million years ago to the present and is often referred to as the “Ice Age” or “Age of Man”. This time period can be divided into two epochs, the Pleistocene Epoch which was from 1.8 million years ago to 11,000 years ago and the Holocene epoch which was 11,000 years ago to the present (Mann 2015). During this time, the continents were moving, and the earth’s orbit was changing, leading to major climatic changes. These changes affected the megafauna of the Quaternary time period. The fauna had to migrate, to adapt, or to go extinct. The term megafauna comes from the ancient Greek word “megas” meaning large and the new Latin word “fauna” meaning animal. Another theory for the extinction of the megafauna is the introduction of humans into new areas due to migration (Gibson 2013).
Earth during the the last ice age
"IceAgeEarth" by Ittiz - Own work. Licensed under CC BY-SA 3.0 via Commons - Link
The Earth was dramatically changing during this period. The tectonic plates and continents were changing their configuration. The continents of Europe, Asia and North America were slowing drifting to the north to their current location.
As the plates moved, the ocean current between the Pacific Ocean and the Arctic Ocean closed and did not allow for the warm water to move north. Without the warmer waters, the climate in the Northern Hemisphere began to cool. At this time, Greenland's’ ice sheet began to form.
Large mountain ranges like the Himalayas, the Alps, the Rocky Mountain and the Andes continued to form and to reach high elevations. All of these changes caused the global wind and the ocean and energy patterns to change which led to changes in precipitation, weathering, and erosion (Ingólfsson 2015).
The Earth began to wobble on its path, and the tilt of the axis changed. This caused the climate to begin to alternate between warmer and colder. This is known as the Milankovitch Cycle in which the earth's tilt shifts from 22.1 to 24.5 degrees.
Diagram of the earth changing tilt
"Earth obliquity range" by NASA, Mysid - Vectorized by Mysid in Inkscape after NASA image Link.
Licensed under Public Domain via Commons - Link
These shifts affect the amount of sun that the hemispheres receive during the winter and summer months which can affect the climate. The ice would advance and retreat due to these changes. These shifts take approximately 41,000 years to complete (National Geographic 2015). The climate continues to fluctuate. Scientist estimate that the climate has changed at least sixty times.
Graph shows the cycling of the temperature over the last 400,000 years
They have used a variety of evidence to study and predict the climate of this time period. Evidence includes marine oxygen isotopes, fossil records, and evolution of vegetation, oceanographic patterns and computer modeling (Ingólfsson 2015). The foraminifera coils, a small shelled organism, show evidence of the constant fluctuation of the temperature. In warmer weather they coil to the right and in colder weather they coil to the left. The coils have shifted from right to left many times (Lambert 1988).
Coiling of foraminifera from UCMP Berkeley Link
"3579h R Indonesie" by Psammophile - Microphotographie personnelle :
Link . Licensed under CC BY-SA 3.0 via Commons
During the last glacial period the sea levels dropped at least 330 feet (100 meters). This drop created land bridges between Alaska and Siberia, Asia and Indonesia, New Guinea and Australia, British Isles and Europe (Lambert 1988). These land bridges allowed animals and humans to migrate to new continents. The Northern Hemisphere was affected more by the colder climate. The colder climate created large ice sheets which covered most of Scandinavia, North Europe, Canada and North America (Keller 2011).
Land bridge from Asia to North America
"Beringia - late wisconsin glaciation". Licensed under Public Domain via Commons - Link
These glaciers produced ice dams which caused changes in the course of major rivers (Ingólfsson 2015). Approximately 10,000 years ago, the Earth went into an interglacial period, which occurs when the climate begins to warm and the glaciers started to retreat (Keller 2011).
Dark Shading shows location of ice during last ice age in the Northern Hemisphere
"Ice Age north-interglacial" by Hannes Grobe/AWI - Own work. Licensed under CC BY 3.0 via Commons - Link
Dark shading shows location of ice during last ice age in the Southern Hemisphere.
"Iceage south-interglacial" by Hannes Grobe/AWI - Own work. Licensed under CC BY 3.0 via Commons - Link
Sabertooth and dire wolves the drawing by Robert Horsfall, 1913
"Ice age fauna of northern Spain - Mauricio Antón" by Mauricio Antón - from Caitlin Sedwick (1 April 2008). "What Killed the Woolly Mammoth?". PLoS Biology 6 (4): e99. DOI:10.1371/journal.pbio.0060099.. Licensed under CC BY 2.5 via Commons - Link
The cycling of glacial and interglacial periods caused these animals to migrate to areas they were better suited for, to adapt to the new climate or to go extinct. The frequent and rapid changes in the climate led to rapid evolutionary changes; therefore, many of these animals evolved. For example, the caribou, musk ox, and polar bears all adapted to survive in the colder environments (Ingólfsson 2015). Many of the megafauna ate shrubs and grasses known as the “mammoth steppe.” The mammoth steppe was a cold and dry climate vegetation. (National Geographic 2015) The last climate change killed the mammoth steppe which supported the organisms of that ecosystem. When the ecosystem collapsed, many of the animals that could not adapt went extinct. The last mammoth is believed to have gone extinct around 4,000 years ago. Most of the megafauna went extinct during the Holocene Epoch (Ingólfsson 2015). Studies are showing that the long periods of cold did not kill the megafauna, but it was the fast warming that did not allow the animals time to adapt and caused many of them to go extinct (Slezak 2015).
Another theory involves the over-hunting of the megafauna by humans. The humans were able to migrate due to the land bridges that formed during the last glaciation and therefore able to hunt the megafauna.
A new study looks at the DNA found in the bone fossils of megafauna. The bones of similar species look the same. Therefore, without looking at the DNA of the fossil, they would appear to be the same species.
One argument in support of the theory that humans over-hunted was that the climate fluctuated many time so why did most of the megafauna go extinct at the same time. These extinctions coincided with humans’ migration to the area.
This new DNA evidence shows that similar species went extinct at different time. While most of the new evidence points to the climate as the main factor in the extinction of the megafauna, the human hunting impact could have increased the extinction rate. Also, approximately 12,000 years ago humans started to change the landscape of the Earth by farming. As the animals migrated to new places, their food sources changed. There is still the question that if the Southern Hemisphere was not as affected by the Ice Age, then why did the megafauna disappear in the Southern Hemisphere at the same time humans started migrating there? New research is being focused in the Southern Hemisphere to answer this question (Slezak 2015).
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Lambert, David, 1988. The Field Guide to Geology. Edited by Kennedy, Denis, New York: Facts on File. 212-213 p.
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Slezak, M. 2015. Megafauna extinction: DNA evidence pins blame on climate change. New Scientist, Daily News 23 July 2015. Accessed online <https://www.newscientist.com/article/dn27952-megafauna-extinction-dna-evidence-pins-blame-on-climate-change/> Nov. 2015.
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