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Monday, November 4, 2013

The destruction of Planet Earth

Sorry, I just wanted to get your attention.  There is no way (well almost no way) we could destroy Earth*.  In the words of my second favourite comedian**, George Carlin, the world will be just fine.  We may not be here but the world will be hunki dori.

* I've included a way at the end of this blog but it is pretty far "out there".
**My favourite is Bill Maher

It's true we may bring nature to a state where there is no animal larger than a cat remaining on the surface but evolution will refill all these lovely empty ecological nitches and it will do it surprisingly fast  in a wild flurry of evolution.  In one or two million years, we won't recognize the place???

The first people who arrived on any uninhabited  island or continent eliminated a huge range of megafauna.  Most of it was done within a few hundred years.  Then when European man arrived with his modern technology, he destroyed and is still destroying whole ecosystems.

When Europeans arrived in, for instance, North America, Australia and New Zealand, the fauna they saw was but a pale remnant of what was there before the first humans arrived.  The first humans had wiped out anything they could eat.  Then European man got busy, trying, quite successfully, to eliminate even this pitiful remnant and doing his best, as well, to eliminate the first people.    Who eliminate who often seemed to depend on who had the best armoury of diseases that they, but not the other side, were immune to but that's another story.

About the only area that has retained some semblance of her megafauna is Africa and only because animals  evolved escape capabilities as humans improved their hunting techniques.  As our killing methods advanced, the more wary animals survived to breed.  Later European man, in South Africa, had almost eliminated Africa's megafauna when he realized that everything he held dear was about to vanish and set aside large parks and brought back the major megafauna that had survived early man. Once more under the first people but with European killing technology, the animals are on the way out again.

As long as we don't destroy too many animals there are all sorts of animals just waiting in the wings to appear and fill all sorts of empty places in nature at a rapid rate.  I know that sounds pretty strange so let me explain.

Let's use the tail of a monkey as an example.  Our monkey has a prehensile tail which he uses as a fifth hand.  As he travels through the trees, he holds on to branches with his tail, freeing his hands (and feet) to pick fruit.  Any monkey that suffers a mutation that makes his tail less effective has a greater chance of falling and hence of not passing on his genes to the next generation.  This constant removal of monkeys with less effective tails highlights one of the characteristics of evolution.  Once an animal or plant is pretty well adapted to its environment, natural selection has far more to do with keeping animals (and plants) the same  than it has  to do with producing new species.

Now let's suppose that some of these monkeys start to move out on to the nearby plains to use a previous unutilized source of food.  They no longer need a prehensile tail.  Monkeys with less effective tails are no longer selected against and all sorts of tail mutations can be retained in the population.  Let's suppose that a tail is even a disadvantage.  At the very least, it takes resources to make a large specialized tail so perhaps that would tip the balance in favour of monkeys without tails*.  Here something interesting can happen.

*This assumes that the tail is not co-opted by evolution**  into some new function.  If so, natural selection will fit it closer and closer to whatever function it is now being used for. 

**Sorry for the anthropomorphism but you know what I mean.

Genetic sequences to produce some characteristic have actuator genes at the start of the sequence.  They turn the sequence on and off.  You can see this in your development.  You aren't born able to father (or mother) children.  The genes to do this are actuated at puberty. See this neat link.

If one of these actuator genes is mutated in the forest monkeys in such a way that the animal has no tail, that monkey is at a great disadvantage but in our hypothetical  monkey, by contrast, who lives on the savanna,  no tail is an advantage.  Having the actuator gene turned off imparts an advantage and leads to this characteristic being fixed in the plains living monkeys.

Even though the actuator gene is turned off, the gene sequence is still extant.    Without the pressure of a constant selection against animals with less effective tails that was occurring in the jungle, this dormant sequence can slowly degenerate.  Most mutations are harmful and the sequence for a tail will slowly be mutated and degraded.  It is a very slow process.  Occasionally an animal will be born in which the starter gene is turned on and this animal will have a tail.  The longer the time since the actuator was  turned off, the more degenerate the tail will be.  In fact, even though we humans are multi-millions of years away from the last of our ancestors that had a tail, very occasionally a human is born with a vestigial tail.  How does this all relate to a rapid radiation of new species, that I mentioned,  to fill empty ecological nitches.

Suppose now that man has hunted all the jungle monkeys with prehensile tails for their beautiful skins.  This nitch is empty and there are monkeys close by on the plains that occasionally have a "throw back" to a monkey with a tail.  If too much time has not gone by, and the tail is still effective, such a monkey finds that he is much more adept in the trees than his fellow monkeys and he no longer has competition from the much more tree-adapted jungle monkeys since man has wiped them out.  That nitch fills up again and natural selection once again selects for more and more effective tails*.

This process of starting up a disabled genetic code is sometimes called atavism activation and also works in the opposite sense.  For instance, in the ontogony (embryonic development) of a chicken (and presumably other birds) a "dinosaur" tail starts to develop.  Then another sequence actuates which re-absorbs the tail.  Evolution works in wierd and wonderful ways.  If you could turn off this tail absorbing sequence, a chicken would be hatched with a a tail.  To go into all the inns and outs of the way you could produce new species from the genetic material hidden in the present species would get very messy.  This is just a hint. Incidentally, the same sort of thing occurs in the "hand" of a bird with the fusion of the distal bones.  Turn this one off and a chicken will have an "arm" much like a dinosaur.  Also, teeth begin to develop and are absorbed before a chicken hatches.  Turn off these three genes and  Presto "dynochicken".

Of course this all depends on the fact that we didn't hunt all the plains monkeys to extinction as well.  The more populations that exist, the more possibilities there are for rapid radiation of species to fill empty nitches.  Otherwise, evolution has to start from scratch again.

This site gives some amusing  speculations about what might evolve

However, even if we were to eliminate everything except single celled organisms, evolution would once more populate the earth.  It would just take far longer and the results would likely be less recongnizable than if more familiar animals were still alive to radiate into the emptyness.

For that matter, we would be very unlikely to eliminate all humans.  We are like cockroaches.  Very hard to kill.  Our present civilization would become the stuff of legends with these fabulous beings (us) having supernatural characteristics.  Humans of the future would have all sorts of inventive explanations for what uses the artifacts they found were used for. I'd love to be a fly on the wall and hear how they explained, for instance, those little plastic bits that we use to close the bread bag.  If it didn't fall so close to home it would be rather fascinating to see us eliminate ourselves as a species. 

Destroying the Earth
When I talk about destroying the earth, I am talking about the biosphere and taking it back to an environment with only single celled organisms extant.  There is a way and we are pushing the system in that direction.  However even our awesome ability to destroy would be hard pushed to cause this much destruction.  Let me relate a little story first.

In a previous life I worked for a research outfit and we did some work for the Tsawassen ferry.  The Ferry takes off from Tsawassen which is located on the BC coast near the American border.  The bottom shelves off very gradually so they had to construct a causeway of fill to get into deep enough water for the Ferries to dock.  They found that seaweed was collecting in the angle between the beach and the causeway on one side and this thick collection of organic material began to rot.  It was thick enough to be anaerobic and one of the break down products of anaerobic decay is Hydrogen Sulphide.  Besides being smelly, and in fairly low concentrations, lethal, it was turning the nearby houses black.  In those days, the white pigment in paint was white lead and when Hydrogen sulphide reacts with Lead oxide it makes lead sulphide which is black.  We sorted out the problem but that is another story.

It has been suggested that previous extinction events, the production of Hydrogen sulphide from the oceans was a contributing factor.  Let's look at the most widely known extinction; the one that wiped out the dinosaurs.  Apparently a large chunk of rock slammed into the Yukitan peninsula and disrupted a layer of gypsum.  Gypsum is Calcium Sulphate and the extreme heating that occured would have produced acids of sulphur.  The total effect was a shading of the world, perhaps for a few years, and a sharp decrease in photosynthesis.

With photosynthesis largely shut down, the only oxygen entering the oceans would have been by diffusion and many of the oceans probably became deficient in oxygen and even anaerobic.  All the life in any part of the ocean that was depleated of oxygen would have died, rotted and produced Hydrogen Sulphide.  The food chain would have been totally disrupted since it depends on the growth of phytoplankton.    Hydrogen sulphide is highly toxic and would have contributed to the woes of the animal life on the land and in the seas.

At present, we have destroyed many of the fisheries of the world and are turning the oceans into jelly fish cultures.  Places where polluted rivers flow into the sea have huge blooms of algae which die periodically and turn the water dead*.  We are acidifying and warming the ocean.  It is conceivable that we could start a chain reaction by killing enough of the ocean that it depleats the oxygen in other areas which generate hydrogen sulphide and kill even more etc. 

* These areas are not actually dead.  They still grow anaerobic bacteria but to us oxygen breathers this is a close to death as it gets.

It would be so easy to reverse all this but we seem as stupid as a species as we are intelligent as individuals.  Sad.

3 comments:

Frank Chapeau said...

So what did you do to fix the Tsawassen Ferry Terminal? (Pronounced SAWASSEN, with a silent T) I'm really curious now.

William Hughes-Games said...

Sorry about that Frank. I meant to put that in but was called for dinner and never got back to it. We told the company to dig out the first 50 0r so meters of the causway and to put in a bridge instead. The seaweed was then swept through, under the bridge and didn't accumulate. It worked a treat and if you go down that way now you will see the bridge just as you go on to the causway.

Frank Chapeau said...

I've been there and it didn't stink. Good job!