What will ET look like when we meet him/her/it?

Posts tagged ‘DNA’

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 57.8o C (136o F) to -89.2o C (-128.6o 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!

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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.