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How Scientists Solved the Mystery of the Mammoth Disappearance



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Using DNA evidence, migration patterns, measurements of reforestation after an ice age, and calculations of planetary warming, scientists have deduced that the mysterious disappearance of the Woolly Mammoths about 4,000 years ago was chiefly due to environmental changes.

DNA record second to none

Paleobiologists agree, the DNA record of the Woolly Mammoth is second to none. Thanks to the sun-zero freezing of mammoth remains throughout the millennia in the frozen wastes of Siberia and northern Alaska, not only bones and marrow, but flesh, hair and blood have been preserved.

A mammoth unearthed from the extreme northern Siberian tundra in the 1800s was so pristine that, unfortunately, natives in the area carved it up, cooked it, and ate it with no ill effects.

Because the blueprint of the mammoth DNA sequence has been so well preserved—more than half the genome has already been sequenced—bio-labs like those in Japan are seriously intending to resurrect the great beast.

Mitochondrial backtracking has made legions of biologists new scientific Sherlock Holmes. Recovering prehistoric DNA is helping to fill in the missing pieces of the jigsaw puzzle of eons past.

Ian Barnes, a molecular paleobiologist at Royal Holloway, University of London told NewScientist.com that "In the space of just a few years, with a relatively small amount of work, we've gone from not really knowing anything at all about the movements of mammoths to being able to say roughly when a migration happened, where the animals came from and where they went to."

Tracing the history of the mammoths

While mammoth researchers have known for a long time that the beasts first appeared on the continent of Africa some five million years in the past, it remained unclear if the creature sprang up as a relative of the Asian or African elephants.

DNA studies have helped solve that question.

Three separate research groups undertook projects to methodically sequence mammoth mitochondrial DNA. Their efforts in 2006 lifted the veil obscuring the intricacies of the elephant family evolution. The information culled from the bio-research also revealed a common ancestor that all other groups split off from some six million years ago. Mammoths diverged from that group and developed from what today is recognized as the Asian elephant.

Scientists believe that, except for the characteristic large, curving tusks, the mammoths then appeared similar to their Asian relatives. Climate constrained the herd of early mammoths to the breeding grounds in Africa until around three million years ago when they migrated into what later became Asia, Asia Minor and southeastern Europe.

At that time, the mammoths, now a distinct and separate species from the African or Asian elephants, were still hairless and the climate remained mild. But Earth changes were underway. The climate began cooling and soon an ice ages would engulf much of the Northern Hemisphere causing animals—including the mammoth—to adapt or die.

As the climate changed roughly two and a half million years ago, marching into a succession of ice ages lasting 100,000 years, interspersed with 10,000-year interglacial periods, the mammoths adapted. The animals changed into what's called the "steppe mammoth," a clear leap away from their Asian-African origin and well-suited for a colder, less friendly world.

The forests gave way to great grassy plains and as the vegetation changed so did the mammoths' physiology metamorphose, adapting itself to the new environment and a new diet.

"The steppe mammoth's teeth had more enamel ridges to deal with a more grassy diet and a higher crown to tolerate greater wear," explained Adrian Lister of the Natural History Museum in London during an interview with New Scientist. Lister, one of the world's top experts on Woolly Mammoths, is the author of the highly informative "Mammoths: Giants of the Ice Age."

From the information gleaned studying European mammoth fossils, steppe mammoths were thought to have evolved very gradually into the modern day conception of mammoths. The animals appeared in their familiar form about three-quarter million years ago.

Blood sheds light on Woolly Mammoth survival

Because so much of what made a Woolly Mammoth a Woolly Mammoth remains, researchers had the opportunity to actually study the nature of its blood.

They discovered that the mammoth hemoglobin was markedly different from that of today's elephants. While the blood of modern-day Asian and African elephants is poorly adapted to colder climates, the mammoth blood allowed it to thrive. That's because the mammoths' hemoglobin worked well at much lower temperatures. By releasing oxygen efficiently in lower temperature climates, the mammoths ruled their kingdom and flourished.

The adaptation took place through natural selection over many millennia.

As one ice age followed another, the mammoths continued to do well. The mighty herds grew and expanded across continents eventually appearing across the entire Northern Hemisphere as far south as Central America.

The height of the mammoth reign occurred during the last 100,000 years of the past ice age. But then, when the next inter-glacial period began and the ice receded, the mammoths began dying out.

What happened to the Woolly Mammoths?

Although theories over the years have ranged from disease to catastrophic change to human hunting to extinction, biologists have found the most likely reason the gigantic beasts disappeared: lack of genetic diversity.

The key to the mammoths survival for millions of years was linked to their ability to adapt. As the climate changed, so did they.

Yet during the last 100,000 years of their existence they dominated the Earth and subsequently lost their ability to change as rapidly as they once did. Their lack of staying ahead of the climate changes through the process of natural selection led to their demise.

The last of the mammoths

Tiny Wrangel Island located in the freezing Arctic Ocean…it's the forlorn place the mighty mammoths, once dominant and now beleaguered, made their last valiant stand.

Those mammoths made the island their home after they were isolated from the Siberian tundra to the west nearly 9,000 years ago. For 5,000 years the mammoths fought the elements and struggled for survival. Yet in the end they succumbed, most likely from human hunters. DNA records of that mammoth colony show the group was stable, so must have fallen at the hand of Man.

Then, just 4,000 years ago, the last Woolly Mammoth fell onto its side and expired.  

So, it's now known the Woolly Mammoths did not all vanish mysteriously almost overnight. Their genetic pool lacked robustness and had too little diversity. The small pocket that did manage to survive could not escape humans with spears.

A mere 4,000 years ago, after the climate and vegetation changed again, the Woolly Mammoths couldn't escape persistent hunters. While their numbers diminished over several thousand years until only small pockets of feeble survivors eked out a meager existence, they were completely exposed to the most dangerous predator on the planet—Man.

That fact eventually spelled their doom.

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