The principles behind evolution have always stood in stark contrast to those postulated by the bible. I have never read the bible and on the few occasions that I have tried, I have fallen promptly asleep. Since I am only aware of the basics – don’t kill people, don’t steal shit, don’t be gay (oops), don’t have sex outside of marriage (oops again) etc. – I won’t spend a moment longer comparing the two schools of thought. Except to say that only the theory of evolution is a school of thought because clearly you’re a beer short of a six pack if you think it’s okay to stone people to death for eating shellfish. Instead, this blog is about evolution: the concept abhorred and spurned by religious zealots the world over.
I’ve always wanted to use “zealot” in a sentence. Winning!
What is Evolution?
Evolution comes from the Latin meaning for “opening” or “unrolling”… to unfold. In this way I suppose one might say (with a little creative license) that evolution is a story of change. In the context of life on Earth, evolution refers to the adaptation, change and diversification of the many millions of organisms that call our blue planet home, or any other planet in the universe for that matter. In fact, evolution is the REASON there are millions of organisms on our blue planet. This comes down to a concept called speciation; but first, let’s confuse you with an analogy about tuna.
It’s About Legacy, Not Heresy!
It is the goal of every single species, whether pachyderm or phytoplankton, to be successful and the hallmark of success in the animal and plant kingdom is propagating your genes. I.e. knocking up your girlfriend.
If you’re bad at it, there are tens if not hundreds more like you willing and eager to step in and you’ll simply exit this realm without a legacy. This is a terrible prospect for animal and plant species that have to fight tooth and nail or stem and stamen just to exist. Competition is fierce and no matter what habitat on Earth you call home, chances are there are at least 20 creatures that want to turn you into breakfast, lunch or dinner.
If you manage to not get eaten, then you’ve still got to worry about feeding yourself and surviving the elements. So, the next time you think you’ve had a rough day because you locked yourself out of your apartment, try to empathise with a minnow… one of the most preyed upon fish in the ocean.
The biological answer to incessant threat is to procreate like mad so that if you meet your maker sooner rather than later, which is almost always the case in the inherently hostile natural environment, it won’t really matter. To you as an individual, yes, but not to the species as a whole. As long as a species is reproducing and enough of those offspring are reproducing, that species can be viewed as successful.
Now, let’s provide a very simplistic and probably inaccurate analogy about tuna…
You’re a tuna fish and in order to survive, you need to swim fast to catch smaller fish. The larger your fins, the faster you’ll be able to swim (yes, a horribly simplified thesis, I know). The faster you swim, the more food you’ll be able to eat and therefore, the more time you can spend getting sexy with the ladies… i.e. propagating your genes. If you were born with smaller fins, you just wouldn’t be as successful at catching food and in sustaining yourself and getting laid.
What this means is that, in this particular example, the tuna with larger fins (Tuna A) is more successful and will probably produce more offspring than Tuna B: the dude with smaller fins. Please ignore the obvious reference to size being important. I know plenty of girls who would disagree. With Tuna A’s well-endowed fins being inherited by his progeny and with his progeny more likely to survive, the less endowed Tuna B would eventually become phased out of existence!
Over the course of many, many generations, a gradual change occurs within the species that serves to phase out the less beneficial or successful biological traits – in this case, small fins – while encouraging the success of individuals within the species that exhibit the more beneficial biological traits (large fins). It’s a slow process that can take tens of thousands if not millions of years, but what we see is the species changing and improving – evolving – so that it becomes as successful as it can possibly be in its given environment.
I am almost certain that you have heard of the name given to this entire concept. The man behind its conception was Charles Darwin and he called it natural selection.
Image Source: Miami University, College of Arts and Sciences
Jean-Babtiste Lamarck, one of Charles Darwin’s contemporaries and mentors was just as enthusiastic about the idea of evolution and, as we can see here, demonstrates a similar – and much better – example of it than the tuna analogy. The most successful (and well-fed) giraffes were those whose necks were ever so slightly longer and so could reach the more succulent uppermost leaves on trees. Over time and via a process of natural selection, they evolved with longer and longer necks and now they are the most vertically endowed creatures on the planet.
This is the horribly simplified version of Lamarck’s theory, which postulated that a giraffe would stretch its neck to reach the higher, more nutritious leaves on a tree and would then pass on its stretched neck to its offspring. This is just not true. If you get a tattoo of an anchor on your butt, your children will not be born with tattoos on their butts. In reality, the explanation Lamarck provided was quackery to say the least, although he was on the right track. Sort of.
Evolution and Speciation
We can now see that evolution is about change via adaptation to an environment, but sometimes this change happens to such an extent that a whole new species is born. “Speciation” is the mechanism by which this happens and we shall take a closer look at this in a moment. But first, what exactly is a species?
If you put an ostrich in a cage with a finch, they will not make little fostriches, or ostrinches. Even if you put two very similar-looking, yet separate species of finches in a cage, they will not likely find each other sexy enough to bonk and make babies. This is really the defining principle behind the word “species”…
“A group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding”
Thank you online dictionary.
This is how you can tell one species apart from another. They will not bonk and even if they were so inclined, they would not be able to reproduce. Obviously, it’s easy to see that an ostrich is a totally different kind of bird to a finch, but if you’ve consulted a bird book recently (I’m guessing you haven’t), you’ll see that groupings of birds like finches, sparrows and sandpipers are made up of a staggering diversity of species that look remarkably like each other. In spite of this, they will not interbreed. If they do, it’s the exception and not the rule. A House Finch is not biologically programmed to shack up with a Cassin’s Finch, even though – to the uneducated eye – they look virtually the same.
Photo credit: “House Finch” by John Benson. Licensed under CC BY 2.0 via Wikimedia Commons
Why do different species of, for example, dogs breed then? Because they’re not different species. With the help of a stepladder perhaps, a Chihuahua could mate with a Great Dane and she will conceive and give birth to puppies with extraordinary identity issues. But a human being could not reproduce with a sheep. Thank goodness for that or there would be some pretty weird creatures running around America’s notoriously redneck south.
So how does one species become two or a different species all together? Evolution, that’s how! But, to be more precise, differential evolution. To rephrase in English: one species is split into two or more groups – through any of a number of mechanisms – and they evolve differently and to such an extent that they no longer want to bonk each other.
For the sake of simplicity (and the fact that your boss is beginning to notice that you haven’t actually typed anything in a while), we shall focus on only the most common of these mechanisms. It bears the unfortunate name of “allopatric speciation” which makes it sound far more complicated than it really is. Here’s how it works…
A species of, for example, butterfly becomes enormously successful in a topographically voluptuous environment complete with soaring mountains and plunging necklines. These butterflies, as a result, spread out to inhabit both the cooler upper mountainous regions and the warmer deep river valleys between them. The ones that hang out in the mountains rarely, if ever make the journey south to visit their relatives and the same applies to the valley dwellers.
Over time and successive generations, the single species splits into two distinct groups. The mountain flutterbies become adjusted to life in the clouds and develop a unique set of traits that enable them to be successful in high altitudes… such as tiny crampons, oxygen cylinders and thermal booties. The flutterbies that hang out in the river valleys also evolve and develop their unique set of traits, including sweatbands, beer-making and fire dancing.
Eventually, these two groups become so different to one another that they no longer recognise each other as potential partners and they will cease to reproduce. What began as a single species becomes two thanks to geographical separation, differential evolution and eventual genetic drift.
Allopatric speciation helps us to understand why very similar species of prehistoric animals have been found in completely different parts of the globe. Owing to the shifting tectonic plates, populations were separated from each other (just like in the movie The Land Before Time) and evolved in order to be successful in their particular environmental context.
Evidence of Evolution in Humans: Wisdom Teeth
A fantastic example of evolution and how we humans have changed as a species is the wisdom tooth. Many moons ago, when we were still living in caves and clubbing women over the heads in order to impress them, our diets were composed of a great variety of foods, such as grains, fruits, leaves, grasses, nuts and other tough and fibrous things. In order to manage these foods, our jaws were larger and more robust. Our wisdom teeth would emerge sometime in our early adulthood and they were very useful in helping us to chew.
Then we discovered fire or rather harnessed its power. And instead of foraging and hunting for food, we began growing it and farming it ourselves. Our diets shifted to one of softer, more processed foods and there became less and less of a need to have such big, strong jaws, although Ronn Moss from that inane soapie the Bold and the Beautiful clearly missed the memo at some stage. With smaller and more gracile jaws, there became less space for wisdom teeth, which is precisely why their emergence in our early 20’s causes so much trouble for us, including over-crowding, impacted wisdom teeth and revolting oral abscesses.
What’s the use of wisdom teeth if all they do is cause us trouble? The good news is that this once useful biological trait is being phased out via evolution! More and more people are being born with only two wisdom teeth or with none at all! If this applies to you, you can congratulate yourself on being more evolutionarily advanced than your contemporaries. The bottom line here is that wisdom teeth are a biological remnant of a time when we needed stronger and more robust jaws. The fact that our diets have changed, as well as our jawbones, has rendered them largely redundant and unfortunately a bit of a pain in the neck *snort*.
Class Dismissed: Your Take-Home Message
Natural selection, speciation, evolution, genetic drift… these may all sound like intimidating concepts, but in reality they are totally logical and – with the help of some ridiculous analogies – easily understood. By understanding these mechanisms for diversification and change, we are offered a very special insight into the history of life on our planet and just how it is we came to share it with an extremely beautiful and varied biosphere.
While a number of hypotheses have been put forward to explain the diversification of life on Earth, the theories published by scientists, perhaps the most well known of which is Charles Darwin, make the most sense. Or at least to those in possession of an enquiring mind and critical thinking skills.