what happened to the populations of the other animals?
Thu, Jan 23, 2020 at 12:30PM
By James "Zach" Zacharias, Senior Curator of Education and History
What is an extinction event? Nearly people do not realize that paleontologists and scientists have created certain criteria for extinction events. These events are characterized by a abrupt change in the abundance of multi-cellular organisms and a widespread subtract in the Earth's biodiversity. Well-nigh of the diversity and biomass on Earth is microbial and hard to measure then these events are limited to easily observable biologically circuitous components of the biosphere.
Scientists have established three criteria for a major extinction event. The first is that the event must be worldwide. Animals must be afflicted over the entire globe not merely regionally. Second, an extinction event must happen very apace in a brusk geologic time scale. Finally, one-third of all existing species must disappear. What is remarkable is that after these catastrophic events new life, new species, and new ecosystems emerge to fill the void very quickly.
In that location accept been five major such extinction events referred to every bit the "Big Five." The first extinction event goes dorsum 444 meg years agone to the Paleozoic era. The second was the Ordovician where 86% of all life on Earth was eliminated. This was followed by the Devonian extinction event 375 one thousand thousand years ago were 75% of life went extinct. The biggest extinction event was the devastating End-Permian extinction result 251 million years ago where 96% of all species disappeared. The fifth, and most famous, extinction event is the catastrophe that wiped out the dinosaurs chosen the Cease-Cretaceous event. Over the years information technology has gained a lot of notoriety and publicity due to what scientists have called "the smoking gun." A large asteroid hitting the Earth 65 million years ago most the Yucatan Peninsula in Mexico. This created a global meltdown of plant life and ecosystems which concluded the long 250-million-year reign of the dinosaurs. This began the "Historic period of Mammals" with many new mammalian life forms filling the major ecosystems and apace diversifying into many new types.
A diorama representing the habitat of a prehistoric Eremotherium laurillardi (Behemothic Ground Sloth).
Fast forward to 13,000 years agone and what are the theories that explicate why the ice age animals went extinct? What was different during the Pleistocene Epoch when giant sloths, giant armadillos, and huge cave bears dominated places like Florida? Most of the animals that perished at the end of the concluding ice historic period were chosen the megafauna or animals over 100 pounds. Huge multi-ton animals like mastodons and mammoths disappeared along with noon predators similar saber-toothed tigers and dire wolves. Most of these water ice age animals had endured at least 12 previous ice ages and did not get extinct. Why was this one different? Scientists take grappled with this question for over 150 years. Scientists have adult four scientific theories to address this conundrum.
The first theory, championed by Geoscientist Dr. Paul Martin at the University of Arizona, is called the Blitzkrieg or overkill theory. Dr. Martin posits this disappearance of the megafauna was due to a new devastating apex predator that could problem solve, throw objects like spears, and make weapons. Obviously, he is referring to humans. Wherever humans came into new lands, corresponding extinction of large land animals occurred shortly after. In North America, a grouping of humans called the Clovis people arrived about 12,000 years agone. These prehistoric people received their proper name after the big spear points they made which were first discovered in New Mexico. They used these large blades in conjunction with a unique tool chosen the atlatl. This tool enabled them to catapult a spear at high velocity and over a long distance to bring downwardly deadening-moving mammoths and other megafauna. In a brusk fourth dimension span, these animals were hunted to extinction. This created a domino result as the other carnivores that hunted them fell by the wayside. Somewhen, a new equilibrium was established in the ecosystem.
The atlatl is a paleo carved wooden tool used to launch a spear at a high velocity to
bring down large mammals such as mammoths. (Replica) ca. x,000 before nowadays.
In a short 1,000-year span, the Clovis people spread from Alaska to the tip of South America. For unknown reasons, they disappeared, and scientists theorize they became the major aboriginal tribes of North and Due south America. The Museum has evidence of these Clovis People at work. In a instance inside the Prehistory of Florida Gallery at MOAS sits the skull of a Florida bison. If you lot await closely, you can observe what appears to exist a pocket-size rock sticking out from the top of the skull. This is no rock, but a broken piece of the spear point that delivered the deathblow to the animal. The skull was found in the muck of the Aucilla River in Northward Florida. It is carbon dated at 12,000 years onetime – the right fourth dimension for the Clovis people in Florida. This proves that these ancient people were hunting big megafauna.
Other "kill sites" accept been found at Silver and Wakulla Springs, and other sites throughout the continent. Even the Daytona Mastodon excavated in 2011 by museum staff has rib bones with what appear to be butcher marks. These bones were sent to experts at the Academy of Indiana and Cathay merely came back as undetermined.
This bison skull dating dorsum 12,000 years was discovered in the Aucilla River east of
Tallahassee by a University of Florida paleontological team in the mid-1990s.
Populations of large animals seemed to radically decrease everywhere when humans first appear in their ecosystem. 3,500 years ago in Cuba, a smaller species of behemothic basis sloth went extinct. 46,000 years agone, in Commonwealth of australia, large animals like the giant kangaroo became extinct when humans arrived. It is the same story in Europe, Madagascar, and New Guinea. What about Africa? The big animals in that location seemed to take survived simply fine. Scientists who prescribe to the "overkill" theory suggest this may be explained by the fact humans and large animals coevolved and existed together for a long fourth dimension. The big megafauna animals on the continent avoided the dangers of these bipedal predators. When humans crossed over land bridges to new continents and islands, existing animals had no clue to be wary. Many large animals like elephants and mammoths have slow reproduction rates making information technology difficult to proceed the birth charge per unit higher than the death rate therefore compounding the trouble.
Eremotherium laurillardi (Behemothic Basis Sloth) skeleton on brandish at MOAS.
The next theory that some scientists believe is that at the end of the last water ice age a dramatic climate change wiped out many large animals that could not adapt fast enough. Once again, the puzzling piece is the previous ice ages seem to take little effect on megafauna. What was so different at the finish of the last water ice age to wipe out these magnificent beasts?
When the climate changed at the finish of the last ice age, warmer temperatures raised sea levels; this especially affected Florida. The coastline was no longer l miles further east from Daytona or 150 miles further due west from St. petersburg than it is today. Many scientists believe that the climate changed speedily and the grasses inverse too. Enquiry from the Academy of Copenhagen suggested that at the end of the last water ice age a change in the grasses resulted in their turn down. These grasses changed from what was called C-three to C-four grasses, which contain more silica and were far less nutritious. Thus, the animals were not getting the right type of food. This environmental modify in vegetation led to their downfall.
Another environmental effect at the finish of the last ice age was the retreat of the ice canvas. The large ice sheet that blanketed North America and Europe kept the seasons dampened, but as it retreated, it caused sharply defined seasons of winter and summer. This caused the animals to move to new ecological zones and adapt. New plants and terrain caused by sharp seasons in summer and winter created a new balance in the ecosystem. If you could non adjust, you died off.
The demise of the woolly mammoth could teach us much about our effect on other species. Image Credit: George Teichmann
The next theory is that a hyper disease spread swept through the megafauna. Perchance, early human aboriginals moving into new lands carried a illness. It has happened many times before were a disease jumps from ane species to another. Cases of swine and bird influenza are mod examples of this consequence. What if humans or the wild dogs that followed them carried a virus in their gut which afflicted big mammal populations. Unfortunately, there is non much directly prove to support the claims of the small number of scientists who are working on this theory.
The final theory, which was just released in the fall of 2019, suggested a visitor from outer infinite wiped out the large mammals of the world. Researchers have just published evidence suggesting that asteroids impacted about Elgin, South Carolina, and Greenland well-nigh xiii,000 years ago. Researchers at the University of South Carolina take detected in a higher place-normal amounts of iridium and platinum, which could only have come from such an touch on. This could cause a mini ice historic period, which today is called the Younger Dryas effect, which was a temporary render to ice historic period atmospheric condition 13,000 years to xi,700 years ago. This was an aberration in the general warming trends of the period.
Although the last ice age was not a major extinction consequence, roughly 35 unlike types of big mammals went extinct. Did humans cause the extinction or perhaps a combination of ecology changes and hunting working together rubbed out the ice age mammals? Ane of the problems is that the bear witness paleontologist and scientists collect is rarely complete. Whatever the reason or reasons, large animals were unable to arrange to whatever changes happened at the end of the Pleistocene Epoch. Scientists just cannot seem to put a "bulls-center" on whatsoever single issue causing this mini extinction event.
Source: https://www.moas.org/Ice-Age-Extinctions--What-Happened--1-5943.html
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