Joshua Trees, Ice Age Sloths, Extinction, and Climate Change Today

With the end of the Ice Age, the giant Shasta ground sloth became extinct in our American Southwest deserts. This extinction happened as a result of the warming of the continent and invasion of humans into the land 13,000 years ago.  Today, the sloth is long gone, but the consequences of its extinction are still being seen to this day.  The Shasta ground sloth was intimately intertwined with every organism they ate, use, or associate with.  Of course, all organisms that inhabit this earth are intertwined in the same way with all the organisms they eat, use, and associate with both directly and indirectly.  This can be extended to show that all organisms are in one way or another connected.  If one organism is removed from an ecosystem, such as the ground sloth, every other part is affected and must adjust their life accordingly.

Unfortunately, not every organism is able to adjust to every change in an environment.  Such was the case of the Shasta ground sloth.  As the climate warmed, plants that inhabited the Southwestern deserts changed, changing the sloths food sources.  As food sources changed, the sloth could not adjust and as a result became extinct.  As a result, the plants and animals affected both directly and indirectly by the sloth had to adjust to "life after the sloth".  For example, the Joshua Tree was a major part of the sloths diet.  At first it may seem that extinction of something that is eating you might be a good thing.  At first, I could guess, the Joshua tree might have benefited greatly by the absence of a giant animal consuming it.  Long term however, the Joshua tree suffered greatly and continues to suffer to this day.  As the sloth ate the Joshua tree, of course this injured the plant.  However, as the sloth ate, it also consumed the Joshua tree seed which would pass all the way through the sloths digestive tract without being damaged.  Once passing though the sloths digestive tract the seed would find itself in a moist pile of fertilizer, which is an extremely ideal location to find yourself if you are a desert seed in desperate need of moisture and nutrients.  

With this association of the sloth and Joshua tree, the sloth benefited with food by eating the tree.  The
Joshua tree made a trade-off though, being damaged by the sloth as it was eaten, but benefiting from the sloth into the next generation.  The sloth aided the success of the Joshua Tree by likely aiding germination and by carrying the seeds to new locations up to ten miles away.  After the extinction, and up to the present day, only desert squirrels and packrats move Joshua tree seeds today, and only at a pace of about six feed per year.  As a result, the Joshua tree cannot adjust its range anywhere near as quickly as it could before and its range has been shrinking for over 10,000 years now.  How do we know all this?  Scientists in the Southwest have examined caves where sloth dung which tells us what the sloth ate.  Ancient packrat middens also have been examined which tell us where the Joshua tree was and when over the last 10,000 plus years.

With the ability to only change their range six feet per year, the Joshua trees range will continue to shrink in coming decades.  Currently, the climate is warming far to fast for the Joshua tree to keep pace.  This does not mean however the Joshua tree will go extinct.  It will be able to survive in cooler high elevation locations.  As the range of the Joshua tree is reduced however, organisms dependent on it will have to adjust.  For example, many species of rodents are dependent on moisture from the tree during times of drought.  These organisms access water from the tree simply by chewing through the bark to access water.  With the trees gone however, there will be far less water available to support rodents.  And so we see the continued consequence of the extinction of the sloth.

Bringing back the Wooly Mammoth

The last known population of Wooly Mammoths went extinct about 4,000 years ago.  The last population existed on Wrangel Island off the coast of Siberia.  Wooly Mammoths were extremely elephant like in both size and shape.  The big differences though between the two lies in their adaptation to climate.  Modern day elephants are adapted to the tropics.  Wooly Mammoths had fur similar to yaks and a thick layer of fat to help hold in heat.  Mammoths also had smaller ears which helped them hold heat in better.  These adaptations are of course why the mammoth lived in the icy tundra and thrived during the ice age.  As the world warmed, bringing the ice age to an end, suitable habitat and areas of food shrunk significantly for the mammoth.  The warming climate along with increased human hunting pressure at the end of the ice age led to the extinction of this huge mammal. 

Even though the mammoth has been extinct for 4,000 years now, scientists are working to clone one back to life again.  The process is simple in theory.  Scientists must first find a living mammoth cell and extract the nucleus.  The nucleus of a modern day elephant embryo must be removed and replaced with the mammoth nucleus.  Then, this embryo must be impregnated into an elephant mother.  If the embryo survives, a baby mammoth will be born to the mother elephant.  All of these processes are well known and have been successfully carried out, but never for wooly mammoths.  In practice however, this process appears nearly impossible.  The first step of finding living mammoth cells is what makes this so difficult.  But once living cells are found, the rest of the process would be relatively simple.

The preference of mammoths for icy cold habitats is what makes this entire process possible in theory.  As mammoths died in the frozen tundra, there is the very likely possibility their bodies would have frozen very quickly, thus preserving living cells in a frozen state.  Indeed, many frozen specimens of ancient mammoths have been found.  Not a single living cell in these frozen specimens has been found though and the probability of a cell surviving thousands of years even in a frozen state isn't very high.  It is still possible though.  And just the fact that it is possible makes at least a few people want to try.  Just think how awesome it would be to go visit a living wooly mammoth at the zoo.  Or see a wooly mammoth performance when the circus comes to town.  OK, that's sort of silly but just think...

Where Did All the Saber-Tooth Tigers Go?

Actual picture I took of a Saber Tooth Tiger.  I found him right after I had a nice conversation with Bigfoot.  OK, just kidding.  But really, where did all the Saber Tooth Cats go???

Where did all the Saber-Tooth Tigers go?  And while we're at it, where did all the Wholly Mammoths, Giant Sloths, and other giant mammals of the Ice Age go?  That's a good question, one that no one really knows for sure, simply because there was no one around at the time to write down what happened.  There were people around at this time would have actually observed these extinctions, they just couldn't write at that time.  The odd thing is, when these extinctions were taking place people were moving into, and expanding rapidly across the North American continent.  The obvious explanation might be that these giant mammals went extinct because of all the people moving into the continent.  However, the people were also moving into the continent because of a recent warming in the climate.  So maybe the animals went extinct because of the change in climate.  There are several explanations for these extinctions which scientists have hotly debated for decades.  Lets take a look at a few of the more prominent ones.

The most widely known explanation for the extinction of large mammals at the end of the Ice Age is over hunting by humans who recently colonized the continent.  This is a very simple explanation, humans, new to the continent simply hunted the large mammals until there where no more.  The problem with this hypothesis is that the human population was probably not dense enough to exert such a huge hunting pressure.

A second explanation is the climate change at the end of the Ice Age.  Warming caused a change in the available food for all animals.  This caused starvation of large herbivorous mammals, therefore causing the predators to starve also.

A third explanation is that when humans invaded the continent, they altered the ecosystem so that it could no longer support many large mammals.  Of course hunting played a role in this, but also as humans consumed plants, and used fire to alter the ecosystem.  As humans ate certain plants, animals had to change their food sources.  As humans burned areas with fire, say changing a forest into a grassland, only certain animals could survive.  Basically, humans altered the ecosystem in ways that changed food chains, causing some animals to die off and others to thrive.

A fourth explanation is the most complex.  It is that all three of the above played a role in the extinction of large Ice Age mammals.  Through a combination of a warming climate changing food sources for animals, hunting by humans, and human alteration of ecosystems by use of fire and harvesting of plants and animals, large mammals went extinct.  This seems to be the latest consensus of the scientific community.  Different species of animals would have gone extinct as a result of different factors.  Some may have been hunted to extinction, others died as their food source changed, and others died as their ecosystem changed.

All this has huge implications for our world today.  Today again we are going though a change in the climate.  Plants and animals are having to adjust what they eat and where they live as the weather warms.  Humans also are changing the landscape in very drastic ways, also causing animals and plants to change where they live.  Basically, those that are able to survive and adapt to these changes will survive.  Those that can't will die off.

Oh-ya, there is another explanation for the Saber-Tooth Tiger that a few people support.  That is, that the Saber-Tooth Tiger is still living today, probably hidden away in some remote forest cave as a pet of Bigfoot or the Lock ness Monster.  Hmmm...

A man about to be eaten by a Saber Tooth Cat.  The man has no idea what's coming.