What do you mean, “not that kind of evolution”?
I am a scientist, and a fairly broadly educated one at that, and so I can have a tendency to forget that a lot of things I take for granted are, in reality, quite complicated for most of us. Like, you know, quantum mechanics. Or much of basic mathematics. Both of those, however, are not what I’ll be talking about today. As you may have guessed already, today we’ll be talking about a branch of science that is very often misunderstood and misinterpreted, despite being rather simple and straightforward in essence: evolutionary biology. Or, as I’ll call it for readability’s sake, the science of evolution. Let’s see if we can evolve these brains of ours, eh?
The basis of evolution lies in one very well known principle: the so-called “survival of the fittest”. This, however, is where many people already stray in the wrong direction, because ‘fitness’ can imply a few different things. It does not, in fact, have anything to do directly with the health or bodily condition of an individual. Rather, we need to think more along the lines of ‘fitting in’: that individual who is best adapted to its environment is the ‘fittest’. And logically, such an individual will simply have the highest odds of living a long, healthy life in that environment than an individual that’s less adapted to the circumstances. This is also known as natural selection: nature “selects” for desirable traits.
Okay, so the ones who fit best, survive. Then what?
Hold on, we’re not there yet! You see, typically, an individual that lives longer will also produce more offspring – many birds, for example, have yearly mating cycles, so every year you’re alive is another year you can become the proud mommy or daddy of yet another set of baby birds. Now, this is where things get interesting.
Your genetic makeup determines in large part who and what you are: within the strands of DNA contained in every cell of your body, is all of the information required to make a basic ‘you’. The information contained in your genome (pop-up explanation: your collected genetic information) is what we call your genotype. In addition, you’ve also got a phenotype: this is every attribute that an individual actually displays. This may include things determined by one’s genotype, but also includes those bits of your behavior, appearance, etc. that are not shaped by your genes alone. Think of things such as learned behavior, hairdressing, etc. Your genome is a combination of that of your mother’s and father’s: in principle you’re comprised of a selection of 50% from each. However, there’s a very important catch: genes can mutate randomly. Usually, these small mutations don’t do anything that’s noticeable on the outside. However, on the odd occasion that they are relevant, they may produce a variety of effects: from nasty hereditary diseases to a hair color entirely strange to your family line.
Now, returning to our bird families, it’s important to realize that the ‘fitness’ of the birds in question is for the larger part decided by genotype: their genetic makeup makes them into the specific species of bird they are and defines all of their characteristic traits. Let’s take the common sparrow, for example. Their feathers are colored in such a way that they don’t stand out against forest or meadow backgrounds, giving them a potential advantage: if your predators can’t see you, they can’t eat you. Now, imagine what would happen if, through random gene mutations, one specific sparrow were to develop a pattern of spots that was slightly different from all of the other sparrows, giving them an ever-so-slight advantage against housecats. Now, it probably won’t double his expected lifespan, but let’s assume it just gives him one extra year – one extra nest of adorable little baby sparrows. Taking the average lifespan of the species to be roughly ten years, that’s a solid ten percent increase.
Now, this change was genetic: this means that upon breeding, his babies have a chance to inherit the gene for the new spot pattern. This, in turn, also gives them an extra year of breeding, giving them, relatively speaking, a larger amount of babies than other sparrows. Now, let this continue for a few generations, and suddenly you will find that most of the sparrows in the population are adorned with the new spot pattern: since it improved survival rates, it was allowed to continually grow in prevalence.
Now, I just made up an example, but there’s plenty of examples in history. Take the giraffe for example: in a time where food was scarce, even a slightly longer neck helped you reach those branches that other individuals from the same species couldn’t reach. As such, long-necked individuals survive longer, resulting in more babies for them, which in turn also have longer necks (if they’re lucky, due to more random mutations even slightly longer than their parents’ necks). And so it continues on and on for a hundred years, a thousand years, a million…. Given enough time, any advantage, no matter how small, may prove relevant enough to spread throughout a population.
This, in essence, is what evolution is: gradual changes in a species because of natural selection. Once you have a very basic understanding of how genetics works, it’s really just the result of applying logic: which mutations are most likely to permeate throughout a species? Exactly: those that allow the individuals in question to spread those genes around. Positive feedback, ladies and gentlemen! That’s all there’s to it. And that, given a few billion years, is what eventually gave rise to myriad of species that exist on our planet today: different conditions favor different genes. Stack all those differences in genome on top of each other and you’ll get every single living organism. From bacteria, to monkey, to snail, to sponge, to owl, to Venus flytrap, to dinosaur – all of them originated through this very basic positive feedback loop.
I hope all of you enjoyed this little foray into the realm of evolution. I may not be a biologist, but there are few scientific theories more important to our modern way of thinking than Darwin’s theory of evolution. As such, I hope that you’ve learned something new today, or else got a chance to reacquaint yourself with an important part of the history of human knowledge. I’ll see you all next month, and remember to stay curious.
Further reading:
As usual, Wikipedia is great if you want to just dive a little deeper into a given subject – this tends to be especially true for scientific article, and I can at times wander through pages for hours, clicking back and forth through topics within an interesting subject. For example, you could try:
http://en.wikipedia.org/wiki/Evolution
http://en.wikipedia.org/wiki/Natural_selection
http://en.wikipedia.org/wiki/History_of_evolutionary_thought
as well as most other articles within the evolutionary biology series. Have fun!
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