Unbelievably, I still get asked about evolution. How can I possibly believe that we evolved from monkeys? If we did evolve from monkeys, then why are there still monkeys? There are people out there who just don’t want to accept the evidence, the mountain of evidence, that’s been gathered over the years.
So instead of replying individually to all the questions, I wanted to put together a single post that contains the relevant information.
Evolution, Natural Selection and Speciation
If you browse the comments on this blog, you’ll see me saying “Don’t confuse evolution and natural selection” quite a lot. And it’s an important point to make. To understand how we came to be in the form we currently are, you need to grasp two concepts, Evolution and Natural Selection. So let’s look at them in turn.
Evolution is how we describe the changes in organisms between generations. These changes are mutations, changes to the genetic material of an organism. You can see them in every day life, just look at the attributes, or traits, children have that the parents do not. Children do, however, share many traits with their parents, inherited traits.
As discussed above, the traits of an organism may be inherited from its parent or not. For a parent to potentially pass a trait on to its offspring, it must survive long enough to reproduce. The theory of natural selection tells us that those organisms that are best suited to their environment are most likely to reproduce. When people talk of “survival of the fittest”, fittest refers to fitness to their environment, or suitability.
The upshot is that the organisms that are best suited to their environments are more likely to survive, and are also more likely to pass on their traits to their offspring. Therefore, their offspring are more likely to be well suited to the environment. This in turn makes them more likely to survive and breed, and so on. It’s a beautifully simple concept at its core. It’s worth mentioning at this point that mutations, even if beneficial to the organism and the organism produces offspring, are not guaranteed to be passed on. Likewise, mutations that are not beneficial to the organism may be passed on to subsequent offspring. There is also the possibility of non-beneficial mutations preventing an organism from procreating but then occurring elsewhere in the same species. A mutation doesn’t just appear once, either succeed or not and then disappear.
When you consider this passing on of traits, you also have to take into account inter-generation mutations. An offspring is rarely identical to its parents, even where a parent pair produce multiple offspring there are differences between those offspring. In these cases, again, the best suited to the environment are most likely to survive and breed. Mutations are hard to predict and rarely follow a defined path.
While genetic mutations are easily observed in the human species, natural selection is not. This is due to our species’ ability to prolong our own lives and help those who are in need of help. We don’t see the weaker members of our species die off before they have a chance to breed. There are, however, mutations that are so severe it prevents that person from breeding. This does not rule out the possibility of that particular mutation occurring in other members of the same species.
While not crucial to the theory of Natural Selection, the way in which species are defined is important. For the purpose simplicity, we can define a species line at the point where organisms can no longer breed. So using the discussion of natural selection and evolution above, if you imagine a species going through these transitions, a new species would be recognised at the point an organisms could no longer breed with members of its former species.
Speciation is an interesting subject, especially when you look at allopatric speciation. Allopatric speciation is where organisms from the same species are separated by the formation of a barrier. Typically this is a geographical barrier. The organisms, originally members of the same species, then evolve independently to the point at which they can no longer inter-breed if reintroduced to each other.
Evidence for Evolution
The ill-informed and the ignorant still claim there is insufficient proof for evolution. This is, of course, ridiculous. There is ample evidence for evolution. In fact, evidence is so comprehensive and robust that the majority of theists have abandoned this course of argument, with many favouring hastily developed reactionary positions such as Intelligent Design. I won’t debunk Intelligent Design here, I’ll hold that for another day.
As for actual evidence for evolution, there is plenty. We have evolution that’s been observed in laboratories (even to the point where it’s reproducible, I called it “Evolution on tap”), observed speciation and thousands of transitional fossils. A transitional fossil represents the preserved (to some degree) remains of an organism that exhibits certain traits which are found in later organisms. These typically also exhibit traits found in much later organisms. They represent an organism that bridges the evolutionary gap between species, in evolutionary terms (although it may be a species in its own right).
We are at a point where we can use evolutionary theory to accurately predict where to find transitional fossils, which period they will date from and what forms they will take. That is the completeness of the theories and how closely tied it is to the discovered evidence. Any sane person would find the evidence for evolution to be so overwhelming as to be incontrovertible.
Arguments Against Evolution
Despite the mountain of evidence there are still those who try and disprove and discredit evolution. I’ve picked out some of the most common arguments I’ve come across and responded to them. As you’ll see, most are either used by the uninformed because they fundamentally misunderstand evolution, or they are used by the informed to mislead
Macroevolution vs Microevolution
If you hear someone roll out this argument, it’s a sure sign that they have a fundamental misunderstanding of evolution. Essentially, proponents of this argument concede that this is ample evidence for evolution, but class all the evidence as evidence for microevolution, and therefore does not qualify as proof of evolution as a cause of speciation. Macroevolution, which is what they claim there is no evidence for, is classed as evolution at or above the level of speciation.
So, to be clear, as proof of macroevolution, they would expect a member of one species to give birth to a member of another. i.e. an inter generation change that is far more severe than those typically seen in evolutionary history. The argument goes that we only have evidence for very small changes as a result of evolution, not the big sweeping changes that result in the formation of different species.
The obvious failing in this argument is that the amount of change that typically causes speciation happens over many many generations and encompasses many different mutations. Multiple instances of microevolution results in macroevolution. To use an analogy, spouting this argument is akin to saying you believe in bricks, because you’ve seen them, and you believe in buildings, because you’ve seen them, but you don’t believe that bricks form buildings because you’ve never seen one part built.
Irreducible Complexity as a concept is particularly popular amongst Intelligence Design proponents. It argues that certain aspects of certain organisms are simply too complex to have evolved naturally and therefore must have been designed (they offer to explanation as to whom designed the most complicated being of all, God). The most famous example used is that of the eye and was one of the cornerstones of the book Darwin’s Black Box by irreducible complexity’s father, Michael Behe. Yes, that’s the same Michael Behe who openly admitted in the famous Dover case, which completely discredited Intelligent Design as a scientific pursuit, that his own simulations demonstrated that the kind of complex evolution he said couldn’t happen could, and in as little as 20,000 years.
Even under the most casually scrutiny this idea falls apart. Taking the eye as an example (as many proponents do), we know how the eye evolved in some detail. Further more, we can look all around us and witness other organisms that have eyes in various stages of development. We do not have the most complex eyes, many species of birds (e.g. Owls) have eyes that are far more complex than our own. We also do not have the simplest, there are organisms with eyes that resemble pinhole cameras (i.e. without lenses and the ability to focus). The evolutionary path of the eye is relatively simple to plot. Even the most bizarre occurrences in nature, such as the bacterial flagellar motor, can be explained. This particular example, one used by Behe himself, was covered amply in Richard Dawkins’ The God Delusion.
The Start of Life
Moving slightly away from the core principals behind natural selection and evolution, many people who accept evolutionary theory still attempt to claim that some sort of deity created the very beginning of life itself, and then allowed everything else to happen (i.e. evolution). I won’t go into this in detail as I’ve covered the origins of life previously.
Why Do We Still Have Monkeys?
Much like the macroevolution vs microevolution argument, anyone who hinges an argument on this question, or any variation of it, has a fundamental misunderstanding of evolution. And you can put anyone who says anything like “I didn’t evolve from a monkey” into the same bracket. This idea that we evolved from monkeys has been pushed in an ill-fated attempt to discredit evolution. Of course, anyone who’s bothered to even look into evolution will know that we did not evolve from monkeys as they exist today but rather we share a common ancestor with monkeys. IDA, as pictured earlier in this post, is a common ancestor to both ourselves and some modern day apes. That creature, or rather the particular sub-species that creature belonged to, would have had mutated offspring at some point. Some of those offspring carried mutations best suited to forest environments and some were best suited to travelling on land. This is of course a gross over simplification, but is necessary without explaining in detail the complete timeline of human evolution. Reading through some of the links I provided earlier on speciation will also give reasons for the parallel evolution of species or one species breaking away from another which remains static.
I hope this very brief introduction to the fundamental principals of evolution, written by a layman, helps you understand the theory. Evolution, and natural selection, is phenomenally simple at it’s core. It is a concept of such beautiful simplicity that I believe it’s not been matched in terms of human thinking before or since.
What do you think about evolution? Is there anything I’ve missed out? Are there any questions you get challenged with regularly that you’d like me to respond to? Let us know in the comments.