Variability and evolution

Last post, I asked: would life in a stable environment evolve past the primordial ooze stage and what level of environmental variability is good for the evolution of intelligent life?

One of my college professors described evolution quite simply.  He wrote, “Evolution is change” and left it at that.  I’ve spent a long time trying to add qualifiers to that definition, because I, an individual, change and individuals cannot evolve.  I’ve always thought that as a model, the “evolution is change” definition is too simple to be really valuable.  Mathematically, though, that particular definition of evolution is useful.  If one defines evolution as change, finding the rate of evolution in a population becomes a calculus problem.

There are two competing theories about the rate of evolutionary change, punctuated equilibrium and gradual change.  The punctuated equilibrium theory argues that, because we see relatively few individuals in the fossil record in the process of speciation, speciation and evolutionary change happen quickly (thousands of years rather than millions).  Then species remain relatively unchanged for the remainder of their history.  The gradual change theory argues that the fossil record is not nearly complete so we should not expect to find examples of speciation, and that evolutionary change happens slowly but consistently.  I think these two theories are both present in the natural world, and the two theories can be combined.  Check out my super simplistic illustration of the concept below!

 

 

The chunks where rapid evolutionary change occurs would be caused by a big change in the organism’s environment.  Most of the time though, chunks of gradual evolutionary change would be caused by small changes in the environment and other processes on a small scale.  A stable environment could hold organisms that evolve intelligence, but I think evolution would be slow.  Instead of the 3.6 billion years it took to get us and our industrialized society, it would take what?  7 billion years?  14 billion years, the entire life of the universe?  Thankfully, our star is pretty young, so it might be possible for a species from a stable environment to evolve intelligence and then come find us as we evolved intelligence.  I don’t think it’s likely though.

What level of variability is good for intelligent life?  We can look at major sources of extinction and evolutionary change in the past to find about the stability of our environment.  Here’s a brief list of possible causes for major extinctions: Temperature shifts, atmospheric changes, shifts in our magnetic field (look at Mars!), food sources vanishing, competition.

Earth has a relatively narrow temperature band (compared to Mercury, or the prison planet in Chronicles of Riddick) from 57.8^o C (136^o F) to -89.2^o C (-128.6^o F).  Water doesn’t even get to boiling, here!  Our atmosphere has had some pretty extreme shifts in the past but it’s been pretty stable for a long time now, with a Nitrogen, Carbon Dioxide, Oxygen mix that suits us well.  The magnetic field has also been consistent for a long time, preventing solar winds from removing our ozone layer.  Our ozone layer is important in preventing radiation from frying us.  Life in general can deal with extremely variable environments but intelligent life needs a relatively stable abiotic environment in order to evolve I think.  However, I also think that the biotic environment (competing organisms, prey species, etc.) needs to be fairly complex in order for intelligent life to thrive.

Sorry, folks.  This post was not as exciting as the last one.  However, if someone knows of an equation that’s been used to express the concepts above, I would give you an honorable mention in the next post if you could bring it to my attention!

Dad: Do NOT read this post!

I love you but I’m serious, Dad.  Turn off the computer now.  Mom, I love you too, but you also need to not read this.

Ok, now that my sensitive parental units have left the virtual room, it is also time to say this post has content that some would term “mature”.  So anyone under 18 needs parental guidance in order to read this post.  (Sorry youngest sibling, you’re out of luck.)  Thank you.

*elevator music*

Not that long ago, I was reading the Cosmo website (I ran out of books OK?? I almost DIED before I got to the bookstore!!) and I found an article touting the song Everlasting Light by the Black Keys as great sex music.  You know what?  It’s totally true!  When I (and an unnamed male) tested this hypothesis, I was not, Not, NOT thinking about evolution, reproduction or even my original hypothesis.  My higher brain functions weren’t even really a part of the process at that point.

Insects mating on a liatris flower head. (Photo credit: Wikipedia)However, I recently heard the song again.  At first, I thought about the night I (and another) tested Cosmo’s hypothesis.  Who wouldn’t?  But then I started thinking about sexual reproduction.  How sexual reproduction has led to enormous variation.  Why sexual reproduction is great.  And then I thought, would intelligent species need sexual reproduction?  Which pretty much transported my whole sexy thought process into a new, strange, geeky dimension.

I recently read a really funny (and really accessible!) evolutionary biology book called “Dr. Tatiana’s Sex Advice to All Creation”.  In it, “Dr. Tatiana” dispenses advice on strange penises, monogamy, sex ratios, complex mating rituals, parental care and more, all the while explaining scientific concepts and making readers giggle hysterically.  The most relevant chapter to this post had to do with asexual reproduction.  Many people confuse sexual reproduction with internal fertilization.  The book defined sexual reproduction as exchanging genetic material with another.  Fish that spawn, bacteria that lyse and allow their genetic material to be taken in by other bacteria, flowers that use bees as an intermediary, all participate in sexual reproduction.  Internal fertilization is what humans (and many other animals) do in order to complete the process of exchanging genetic material.

Asexual reproduction is not that rare.  Certain plants, animals, and single celled organisms participate.  The interesting ones, however, had sexual reproduction in the past and evolved asexual reproduction.  The book provides many examples of this exact phenomenon.  Why?  What is so great about asexual reproduction?  Asexual females (sounds like an oxymoron, doesn’t it?) only need to produce 1 baby to keep the population stable compared to the 2 babies a sexual female needs to produce.  Additionally, all that energy and time sexual beings waste trying to find a mate and doing the deed?  Completely unnecessary.

If asexual reproduction is so great, why don’t we all do it?  Our planet is variable.  Not only do seasons and weather vary in most places, but scientists are discovering cycles in temperature and precipitation that occur on geologic time scales.  Our predecessors evolved sex in order to create variability in their offspring. One of us might get lucky and have a gene that supports survival when the environment changes to X.   We as sexual beings have more variation among ourselves than do asexual beings.  Therefore, when environments are stable, sexual reproduction is kind of a pain.  However, when environments are variable, sex is great.  Extra-terrestrials would not need sex if their environment was stable (or only variable enough for mutation to take care of any issues).   On the other hand, Cosmo would totally not translate to intelligent asexual beings!  Maybe that’s a good thing.

Next post subjects: would life in a stable environment evolve past primordial ooze stage and what level of variability is good for the evolution of intelligent life?  Also, the Drake equation, the Fermi paradox and SETI.

Dark Armies of Primordial Ooze

Once upon a time, two globs of primordial ooze met and fell in like. They then decided to form a Dark Army to compete with other globs of primordial ooze! Dark Armies of primordial ooze have evolved at least twice, once in plants and once in animals. What about multicellularity is so great?

Most modern life forms have cells contained by phospholipid barriers. There is probably a maximum size limit to the amount of space that can be contained inside the phospholipid barrier. Until the evolution of multicellular organisms, that meant that the size of the organism was limited by structural components of the cell. After this evolutionary leap forward, the size of the organism was no longer limited in this fashion. Multicellular organisms would therefore be able to out-compete other organisms where size confers an evolutionary advantage.

All life would begin as single celled organisms, but on most planets, I think this advent of multicellularity would occur. Your assignment, O (hypothetical) reader, is to comment on environmental conditions where large organism size would or wouldn’t impart an evolutionary advantage. Fred Meyer has a 1 hour internet time limit, so tissue differentiation will have to wait for next time!

Thesis…

As a life-long science fiction fan and an aspiring evolutionary biologist, I have given a great deal of thought to the presence of extra-terrestrial life.  For the purposes of this blog, I am going to assume that extra-terrestrial life exists somewhere in the universe.  To all the party-poopers who would argue with me I have several points to make: 1) The universe is vast and among all the uncountable combinations of stars and planets and moons, it is likely that there is a planet similar to Earth orbiting a star similar to our Sun somewhere out there.  2) Life evolved on this planet relatively quickly considering how complex and strange our basic chemical makeup is (DNA is nothing short of astounding when you examine it closely!).  Meaning that life may take a while to happen but it could happen on any Earth-like planet.  3) It’s just more fun this way! Also I really don’t want to argue creationism with anyone, so if you try to make this post about your religious beliefs rather than a science-fiction-y exploration of complex life, I will ignore you.

Given this assumption that extra-terrestrial life exists, the next question is what would it look like?  What kind of adaptations would an alien species exhibit? By looking at our own evolutionary history we can throw out some ideas about what we might see upon encountering this alien race.  Unfortunately, I speak Bio-Geek almost exclusively so I need to define some terms so people will understand me.  First, evolution is the total processes resulting in species differentiation, including natural selection (survival of the fittest), mutation (survival of the freakazoids), genetic drift and bottlenecks (survival of the lucky).  Second, convergent evolution is when two species in different groups evolve some characteristic for generally the same purpose but from different starting points.  The classic example is flight.  Flight has evolved in at least three different groups on Earth (birds, bat and insects) for the purposes of escape from predators and pursuit of prey.  Convergent evolution is important because it means that the evolutionary pressures driving a species, towards flight for example, are fairly consistent and we can generally assume they would be consistent on another planet.  Third, stochasticity is randomness or unpredicatability in processes.  The prevalence of stochasticity basically means that if we should meet aliens tomorrow, I cannot be held accountable for the differences between my predictions and reality.

In this blog I intend to point out some chemical and biological factors which are assumed to be present in any ecosystem based on logic and a basic knowledge of science.  As you can probably guess, I also intend to make some loose predictions about alien life by examining convergent evolution in our own evolutionary history.  (I’m already giddy about it!)  We are only likely to meet intelligent races (at least until we figure out that pesky FTL drive) so I’ll give some thought to the origins of intelligence.  Finally, I’ll take some of my favorite examples of aliens from sci-fi and explain why I think they would or wouldn’t exist on a “real alien planet”.  I would welcome discussion about the topics I propose (if anyone actually reads this blog) but please keep it civil and off the topic of evolution vs. creationism.  I am sure there are other bloggers that would love to argue that particular point with you.