Death By DNA

Scientists have been studying the extinction of the woolly mammoth — those colossal, fur-covered, elephantine creatures that thrived during the last Ice Age.  And, specifically, the studies have been looking at the role genetics played in the demise of the shaggy giants with the huge, curved tusks.

example-museum-replica-species-canadian-de-extinctionThe last woolly mammoths died surprisingly recently — about 4,000 years ago, during the Old Kingdom period in Egypt.  By that time, the mammoths had vanished from the European and Asian continents due to habitat change due to global warming and the efforts of human hunters.  The last of the species lived, and died, on Wrangel Island, in the Arctic Ocean north of Russia.

According to scientists, declining numbers put the mammoths on a death spiral caused by inbreeding and genetic mutations that the population was too small to overcome.  With a shrinking pool of mates, and a lack of genetic diversity, the harmful mutations multiplied, affecting male fertility, the mammoths’ sense of smell, and other important functions.  Scientists confirmed this by taking mammoth genes from the Wrangel Island population and placing them in the cells of the mammoths’ nearest living relative, the Asian elephant, to see how they performed.  The tests showed that the mammoth genes were pitiful and failing.  The scientists also compared the genes of the last mammoths with genes from mammoths that existed thousands of years earlier, when vast herds of mammoths thrived during the height of the Ice Age.  The comparison showed that the last mammoths had an “accumulation of detrimental mutations … consistent with genomic meltdown.”

We can’t do anything for the last mammoths that perished on the frozen wastes of Wrangel Island, but their fate shows what happens when the population of a species simply becomes too small to overcome genetic mutations.  It’s a cautionary tale to keep in mind as we look to identify, and protect, the endangered species currently inhabiting planet Earth.

Lessons From A Mastodon’s Rib

Scientists have been carefully examining the rib bone of a mastodon, a giant, tusked, elephant-like creature that roamed North America thousands of years ago.  The bone has led them to some interesting conclusions about when humans first came to the Americas, and what they were like.

The mastodon rib bone is unique because it includes an embedded projectile — a spear-point, also made from a mastodon’s bone, that had been sharpened to a needle-like point.  Scientists have applied precise new dating technologies, including radio carbon tests using atomic accelerators, to the bone and have concluded that it dates from 13,800 years ago.  The age of the bone is significant because it predates the point at which the so-called “Clovis hunters” were supposed to have swept across the land bridge from Siberia and spread across the North American continent.  The needle-like spear point in the mastodon’s rib — which uses bone tool techniques much more sophisticated than those purportedly used by the stone tool-wielding “Clovis hunters” — indicates that humans probably arrived thousands of years earlier.

The bone tells us that the early North Americans were capable of fine and effective toolmaking and were fierce and formidable hunters.  Imagine being able to hurl or thrust a bone spear with sufficient force to pierce not only the hide of a mastodon, but also penetrate its rib bone!  But the bone may tell us something more about the bloody-handed history of our race.  It raises the possibility that early humans played a much larger role than was once thought in the mass extinction of the huge creatures that ruled the Earth during the last Ice Age.  Woolly mammoths, mastodons, sabre-toothed cats, giant sloths, and giant birds all went extinct about 13,000 years ago.  The dating of the mastodon’s rib bone increases the sad likelihood that the fierce, bone spear-throwing hunters standing at the dawn of recorded history hunted those long-lost species to their deaths.

Not Our Fault

A recent study has concluded that the woolly mammoth died out due to declining pasture land, rather than being hunted to extinction by early humans as some scientists have speculated.

Interestingly, climate change apparently played a role — although no one seems to be attributing that climate change to humans (yet).  During the Ice Age, there were smaller concentrations of carbon dioxide, which discouraged tree growth.  As a result, there were vast pasture lands that were perfectly suited to large grass- and plant-munching beasts like the woolly mammoth.  As the Ice Age receded, climates warmed and carbon dioxide concentrations increased, which in turn led to the development of forests that encroached on the grasslands that were crucial to the survival of the mammoths.

The study is based on computer simulations, so there will still be room for debate.  Nevertheless, it is nice to think that our ancestors were not responsible for the extinction of these striking, colossal creatures that roamed the planet at the dawn of mankind.

On The Extinction Of The Giant Irish Deer

Evolution is a fascinating branch of science — not least because the fossil records show that the Earth has, at various times, been home to some amazing creatures.

One such now-extinct species is the giant Irish deer, which suddenly became extinct 10,600 years ago.  It was an enormous animal.  As the attached chart indicates, it was much taller than a modern human, with a massive set of antlers.  Since the first fossils were found in the early 1800s, the giant Irish deer has been the subject of significant interest, with some in that era concluding that it must have died off in the Biblical flood, others speculating that the animals were hunted to extinction, and still others arguing that their massive antlers must have somehow done them in.

Scientists have now conducted tests and determined that the Irish deer died off due to climate change.  Various aspects of the teeth of the animals indicate that the temperature was dropping at the time of their extinction, and the habitat in Ireland therefore changed from being heavily forested to being more tundra-like.  As a result, less vegetation was growing — and these massive creatures clearly needed lots of plants for nourishment.

Imagine, if you will, going back in time to the heavily wooded island now known as Ireland 12,000 years ago, walking through the primordial forest, hearing a sound, and turning to see one of these titanic creatures, towering above your head, with antlers sweeping 12 feet across.   It must have been a magnificent sight.