October Update

Bought a standard poodle puppy.  Bringing him home October 5, so October will be full of housebreaking, and FUN.



Entries in evolution (19)


Evolution Is Amazing

Amazing that only half a century ago we were just discovering the structure of DNA and its method of duplication.  Then came myriad questions about how DNA produces characteristics. 

Before we answered even a fraction of those questions, we discovered epigenetics, the system of molecules that mark and control DNA.  Here came another multitude of questions and discoveries.  Some of those epigenetic markers are methyl groups (a carbon and three hydrogens).

Now John R Bracht has reported on a ciliated protozoan, Oxytricha trifallax, which uses the same methyl groups to mark junk DNA for the trash

According to an article in TheScientist, this organism  reproduces asexually when food is plentiful. 

However, it has an astonishingly complex reproductive cycle for times when food is scarce.  During this cycle, the cell has up to 8 nuclei.  Some of these are used exclusively for preserving the entire genome for reproduction, while others shed over 90% of the genome by getting rid of methylated "junk" sections and keeping only what is currently useful.

And this is all happening in a single-celled creature!  What an awe-inspiring result of evolution. 



Avoiding the Uh-oh of Global Warming

I wonder if the new "anti-science" stance on the right is just a political form of denial.  If our leaders tell us that scientists are know-nothing, left-wing commies, we can pretend climate change is a myth. 

If politicians say that evolutionary biology is a godless, communist plot, we can pretend they have nothing to teach us about the overuse of antibiotics or the dangers of tens of thousands of pollutants in our air, water, and food.

If someone running for President or for Congress tells us that the rich need more tax breaks so they can create more jobs for us little people, we can pretend that corporations aren't laying waste to our democracy and opportunity for all.  We can pretend we don't have to do a thing to preserve our country: we don't have to be vigilant or hardworking or brave.


A Time to Every Purpose

A few years ago I read a wonderful book by Marc W Kirschner and John C Gerhart called The Plausibility of Life.  One point the authors make is about the Cambrian Explosion, when all the animal phyla evolved.  The reason no new animal phyla have come about since then, is that animals in an incipient new phylum would just get eaten by much more specialized animals and other organisms that are already around.

         In Stephen J Gould’s Wonderful Life, Gould makes the point that rather than being shaped like trees, the evolving animal phyla stop branching after a while and start to taper, as more successful species and genera thrive and other, less successful ones go extinct.

         Now I’ve come across an amazing quotation from Charles Darwin about the evolution of organic molecules, though he knew nothing of DNA:

         “It is often said that all the conditions for the first production of a living organism are now present, which could ever have been present.  But if we could conceive in some warm little pond… that a …compound was chemically formed ready to undergo still more complex changes, at the present…such matter would be instantly devoured…which would not have been the case before living creatures had formed.”

         So there was Darwin, at the threshold of figuring out the mechanism of biological evolution, already figuring out that once evolution has reached a certain point, it can’t go back again.  I am gradually realizing what genius it took to come up with Darwin’s understanding of evolution.





Love Me, Love My Bacteria

My June 19 post was about the exciting study of our microbiomes.  A microbiome is the entire assemblage of bacteria that live in any one human being, or other animal.  Your microbiome is different from mine.  We might have a lot of the same species of bacteria inhabiting our bodies, but in different amounts.  Or you might have some species I don't have, and vice versa.

We now know that only 10% of our cells are human.  The other 90% are bacterial.  Since our species, and for that matter, all animal species, evolved in a bacterial world, we depended on our resident bacteria from the very start.  We actually can’t survive well without them  In fact, maybe we shouldn’t think of them as “resident.”  Maybe we should think of them as part of us!

         Vast quantities of bacteria live in our gut.  They break down food, like cellulose from plants, that we can’t break down ourselves.  They manufacture vitamins we need, like the B-group and vitamin K.  They regulate the amount of acid in our stomachs.

         Recently, researchers have begun to think some of our bacteria actually “teach” our immune systems how to function.  In particular, our bacteria may regulate our "killer T-cells," such as the one in the micro-photo I've posted today.

         How amazing: we may have evolved to need certain bacteria to regulate the immune systems we had come to think of as nearly supernatural in their ability to fight off infection. 

         How intriguing: this immune regulation may have something to do with rising rates of asthma.


We Are (Definitely) Not Alone

I’m always bedazzled when I realize that we live in a bacterial world.  Nothing shows quite so graphically the power of evolution.  Bacteria, especially “friendly,” useful bacteria, are the dark matter of our lives.  And we only become aware of them when they go missing and something goes wrong.

         I’ve mentioned before the strange business of increasing rates of asthma and other allergic conditions in present-day children.  Strangest of all is the fact that rural children, especially farm children, don’t seem to be affected.  Those kids don’t suffer from the over-sterilized city world of anti-bacterial soaps and cleaning solutions.  Apparently, when children are exposed to an enormous variety of bacteria from birth, they are protected from allergies to some degree.

         Recently, research has begun to show that our protective bacteria inhabit every part of us they can get to, and that we contain enormous numbers and kinds of bacteria.  These guys are being called a “microbiome,” and each of us has our own, different to some degree from everyone else’s. 

         We begin to pick up our own microbiome as we pass through our mothers’ birth canals.  (Children born by Caesarian section have higher asthma rates than those born vaginally!)  After birth, we continue to pick up bacteria from the air, from food, and all sorts of sources..  Every part of our bodies that is exposed to the outside becomes inhabited by an enormous variety of bacteria. 

         And it turns out we really need these bacteria for nutrition, for protection, for the proper functioning of our bodies.  All those anti-bacterial products we use to get rid of “germs” are making some of us sick, or obese, or who knows what else? 

         A good example of people trying  to re-do what the Cosmos has already done much better.  We need more humility.