Three Schools (With a few sub-divisions)
The arguments I hear seem to come from three schools of thought. First, we have the Creationists, both of the Old Earth and Young Earth persuasions. Second, there is a broader group which I call the 'Neo-Creationists', which appears to be made up of Creationists who shy away from mentioning a Creator and an Intelligent Design contingent who don't mention a specific designer. Lastly, we have the purely materialist views on evolution, with or without frank atheism. Each school has their favorite set of arguments, some of which are more compelling than others, so I thought it might be good to think about some of them.
As I understand their arguments, the Creationists say that God created all species in approximately their present form. The Young Earth group believes this world (and I suppose the universe as well) to be less than 10,000 years old, and when geologic features such as the Grand Canyon or fossils are mentioned, they say that Noah's flood did it, and God threw in the fossils to lead the unbelievers into error. Since this is clearly an unfalsifiable claim, there is no point in examining it further as it is impervious to any inspection or argumentation.
The Old Earth group allows for the evident age of the earth and universe but also claims God created all species as they exist now (and must have done so with other, now extinct species as well). This argument seems to have fewer obvious defects than the 'stricter' Creationists, but if it is true, it leaves me wondering why God decided to kill off the 99.9% of the species that went extinct in the past. Was He just having fun? Didn't He really know what He was doing to begin with and had to experiment a lot before He got things where He wanted them? Although one can never claim to directly know the intent of God, to me this scenario seems to paint Him as either a little frivolous or not nearly as competent as we would like to believe.
This group seems to be saying, in effect, that life, both the individual species and the ecology in which they live is just too complicated to have sprung up by random events. In other words, it is akin to throwing handfuls of parts into a drawer, shaking it and pulling out a finished watch – in other words, a variant on the Watchmaker Argument which goes at least as far back as Issac Newton. This argument was, and continues to be compelling to many people since it meshes with ordinary observations about the world around them. Now, if you did that in one of my drawers, you might actually be able to pull out a watch, but that is another story entirely...
As far as I am aware, all of this group seem to believe that because of the issues of complexity, one species can not evolve into another, and thus each species must have been made separately. They also point to biologic structures such as the eye, among others, saying these are clearly too complicated to have originated spontaneously. A probabilistic argument is also used, where it is computed that there is not enough time in the history of the universe for even a single specific protein to have been assembled by randomly combining its various amino acids. The argument here is that there must have been a Designer (Intelligent Design, or ID) who figured out how to build all of these plants and animals, either individually, or as some of this group believe, at least make a lot of the basic parts available (just like my drawer, which actually is full of watch parts...). Without getting too far into the weeds, the same arguments are also made for the universe itself, since for it to exist as we know it, several 'natural' constants have to be fairly finely tuned, lest everything fall apart.
Although the ID group does not necessarily explicitly mention God as the Design Agent, the arguments seem to be just a ‘God-Lite’ version of those put forth by the Old Earth Creationists and have some of the same defects – it points to a really bad Designer. I have heard it suggested elsewhere that this universe is actually some alien teenager's first attempt at a high school (alien) science project, which now languishes in his closet because he didn't get a very good grade on it. This would explain why some things (like people's lower backs) are just so badly designed...
As I see it, a principal problem with this view is that it becomes either circular or duplicative. If there is indeed a ‘Designer’, then he (it?) either was here all along and forever – which is pretty much a definition an immortal God, which gets us back to pure Old World Creationism, or, the Designer itself arose spontaneously and evolved from lower forms, which negated their original argument – that nothing like this can occur spontaneously from mere matter. This major issue aside, unlike those from the Creationists, these arguments look perhaps falsifiable if the claims can be examined one at a time, and it looks worthwhile to examine them further.
Although not specifically atheistic (as it is with Richard Dawkins), this group denies any type of non-material agency is required to explain either the universe, the origin of life or its evolution into ourselves (or the alien with the science project). Arguments here are effectively mirror images of those from the ID group, so these two sets of arguments can be examined together. We might as well start at the top...
The 'Hard' Problems
The Origins of Life
This, or speculation about the origin of the universe itself does not really have anything to do with evolution, although it is an interesting problem in itself. One argument for considering it apace with those for evolution, is if it can be shown that life could not have arisen without a non-material Agency, it would go a long way to bolster the non-materialists' arguments. It has also been posited that life on earth may not have originated here but was the result of 'seeding' this planet at a suitable time in its past, either deliberately by some unknown (but material) species or by accidental interplanetary ejecta from a world with existing life. This is not as nuts as it first sounds; you can't get complex organisms here that way, but some hardy micro-organisms may have been able to survive such a trip. However, even if this were so, it still leaves the question of where life arose originally, no matter how many hops it took to get here.
The premise we need to look at would have to be “life can not be originated in a purely material system”, since that is falsifiable if someone actually does it, or convincingly shows how it could be done. Statements how life actually originated can not be usefully examined, since no was around at the time. Earliest fossil records are mainly stromatolites, which were probably more complicated than whatever qualified as the 'first living organism', so we are left with showing out how it could be done, rather than with direct evidence. This is where the ID arguments from complexity start to come in.
Without having to go into the math, you may take my word for it that if you had pots of each of the 20 amino acids found in our genetic code and make up a typical protein, and if you randomly chose one molecule, then another, etc, and stuck them together to make a protein, there would not be enough time since the universe began to randomly duplicate, for example, the common protein albumin, which is found in egg whites, among other places. The argument then goes: “If it is impossible to randomly duplicate just one protein, just think how impossible it is do duplicate thousands of them, not to mention stitching them together into even the simplest cell!” This is a very compelling argument and absolutely true – if you accept the initial premise that albumin (or any other protein) started off that way. But they didn't, so this argument is misleading on several counts.
Neither I nor anyone else knows exactly what happened, but the laws of chemistry dictate that mixes of simple materials, over a period of time and under the right conditions (heat, water, lightning – whatever) will combine into more complex ones. Using the mix of simple chemicals which are known to exist on planets without life, a laboratory can mimic the conditions of earth in its youngest days and see the creation of a number of the chemicals, including amino acids, which life requires. But, this still isn't life, so something else is required, which is organization and replication. For something to be considered 'alive', it must get energy from somewhere and use that energy to duplicate itself - “Go forth and multiply”. Crystals are organized and can duplicate themselves – or at least grow, but they aren't 'alive' by anyone's definition (well, maybe some people in Sedona...), so something else must be needed before we consider something 'alive'.
Erwin Schrödinger introduced the concept of negentropy in 1944, as a concept which explains the essence of life, which is the ability to utilize the energy in a system to reverse the entropy of the organism – in other words, we eat and metabolize so we don’t disintegrate. This distinguishes us from other structured, but nonliving matter, such as crystals and viruses. A living organism also has something that physically isolates itself from the environment, such as a cell membrane. An organism obviously also needs some way to replicate itself, which means it needs a way to store ‘assembly’ information. This pushes the problem of ‘complexity’ up another notch, since we now have to posit that an organism would not only have to be assembled from random bits but also the instructions to make it would have to be similarly assembled, and this is a truly impossible scenario. But that may not have been the way things developed, as newer discoveries have hinted.
The 1989 Nobel Prize in Chemistry was awarded for the discovery that RNA, a molecule whose structure can contain ‘assembly’ information, can be, in itself, biologically active. Simple RNA and its precursors can be formed in the laboratory from mixes of chemicals which would have been found in the early earth environment, so it is conceivable that some biologically active RNA could have been spontaneously formed, and since RNA is in itself a set of assembly instructions, it could be self-duplicating. Another interesting quality of RNA is that the duplication is not all that accurate; the ‘mutation’ rate is very high compared to DNA, which is why RNA viruses such as HIV are so hard to eliminate because they constantly mutate in the body, making them a hard target for our immune system. The walling off of a slurry of this self-replicating RNA inside a vesicle would also be likely to occur spontaneously, since many organic compounds spontaneously arrange this way. Thus, if we have a selection of highly mutable RNA walled off in a vesicle, it would be expected that one could see a form of beginning evolution, where those self-actuating molecules duplicated themselves imperfectly. Most would not be ‘successful’, but those that were could duplicate the successful ‘formula’ they carried and go on to populate whatever puddle they were in – ad infinitum. Based on some fossil records, it seems the early earth needed about a billion years to do this...
Life is REALLY, REALLY Complicated
This still leaves us with the ‘albumin problem’ of overwhelming probabilities against its formation, but this is true ONLY if that particular configuration was privileged – that is, if that were the only way to make it, and make it effective. This is clearly not true, as there are huge numbers of albumin-like proteins, and they are all effective for their particular purpose, and this changes the odds completely.
If one were to take a classroom of 23 pupils and ask them for their birth dates, what are the odds that two in the class will have the same birthday? The first thought might be that the odds would be fairly long, but that is wrong; the correct answer is that the odds are about one in two, or 50%. This is the ‘Birthday Paradox’, and the reason for it is that no particular date is privileged, and that even though the odds of a specific date are about 1:365 per pupil, but since any pupil can be born on any date, one needs to calculate the odds of a date NOT being the correct one, and this combination gives the 50% odds. The previous link explains this in more detail.
This goes a long way to explain why the seemingly insurmountable odds of randomly forming a single known biological molecule are not so daunting after all. The correct question is how many ways are there NOT to form a working molecule and compare it to the ways of forming a working one – assuming it is purely a random process to begin with. Since virtually all species have their own particular albumin-type molecule (in this case), it is not a stretch to believe that there are almost an unlimited number of ways to do it. However, this still leaves the problem of complex structures which arguably couldn’t have formed de novo from a collection of random events, the exemplary one being the eye.
One cannot argue the eye is not assembled from a set of biologic instructions passed on at an organism’s conception, since the facts of genetics are well-established; the question is rather how those instructions came to configure the organ in question. With any man-made product, there is always a very long ‘evolution’ of its design and components; the digital computer (or a simple mechanical watch) is the inheritor of a very long line of knowledge, or ‘instructions’, which started from something very simple and accumulated many small changes over its development until the ‘final’ product was realized. In biology, all present-day complex structures have simpler structures which predate them in less complex organisms. In industrial product design, one often sees different ‘models’ developed, and if they find a specific niche, there are product ‘branches’ which diverge from the original one over time – one example is the separate evolution of the gasoline and the diesel engine.
Similarly, the animal eye has different design ‘forks’, where very complex ‘seeing’ structures were developed from what was probably a simple photoreceptor – the ‘Eyespot Apparatus’, which is found in simple one-celled organisms and indicates the direction and intensity of a light source. As organisms became multi-cellular, this was connected to their primitive nervous systems, and from that evolved into the eye types we see today, leaving behind a large number of organisms with sense organs of varying, intermediate complexity, allowing one to visualize the steps along the way. Vertebrate eyes and mollusk eyes look very similar, but they are laid out quite differently, with the mollusk eye being a much better ‘design’; somewhere along the way there was a design 'fork' which left us out... The other major branch of vision is the arthropod eye, which takes advantage (or is constrained by) the construction of an exo-skeletal body. These eye versions diverged hundreds of millions of years ago but have kept their diverse structures because once a branch of a complex organ is made, it is essentially impossible to go back to an earlier version because ‘devolving’ is almost certain to reduce the viability of the organism and hence such changes would be unlikely to be passed on.
Again, although a complex eye could not appear spontaneously, one can see how its design might have grown by a succession of small improvements taking place over eons. Similar structural developments from simple sensor to complex organs can be seen in the ear. This does not argue against a ‘Designer’ who added ‘improvements’ to an old model to create something that better fit an organism for its particular ecologic niche, but certainly says that the complex sense organs did not arise in their final form – only after millennia of ‘tinkering’. It is often pointed out that the most complex organ of all, the human brain, is impossibly complex. That may be so, but complexity does not mean that it could not be formed gradually via evolution. Similar to the sense organs, there are structures in the brain which are identical to those found in less complex animals. These are not ‘hold-overs’ but still perform more or less the same functions as when they first came to be. This phenomenon is seen throughout biology, where some really basic compounds or structures have remained unchanged for hundreds of millions of years, simply there is no better way to perform that function in their environment.
The other problem ID proponents like to bring up is that of speciation; how does one animal turn into another completely different one, as in going from a rabbit to a fox…
Speciation: How Did Fluffy Get To Become Spot?
If one accepts that organisms can change, and that these changes are heritable, then speciation makes perfect sense. A dog is unlikely to evolve into a cat because both are highly specialized for their particular environment and can’t really change without the risk of dying out because the changes would likely be mal-adaptive. Species in a stable ecosystem can remain essentially unchanged forever; for example, alligators, turtles and sharks are so well adapted that they are almost identical to their ancestors of hundreds of million years ago. However, most of the earth is far from static.
Environments change all the time, and geologic changes can easily throw groups of identical species into a new, and sometimes different, ecologic niche. Organism adaptations which worked well in one set of circumstances may no longer work, so those organisms with helpful mutations will tend to survive better and pass along the changes to their offspring. In humans, each individual is estimated to have about 60 mutations; most are inconsequential or harmful, but some may be beneficial enough to be passed on. How quickly mutations can add up is seen in breeding programs (dogs, cats, domestic animals, etc), where human-driven selection can produce a very different looking and performing animal in ten generations or less. However, these are all the same species, or would be for a while.
In the above example, selection was not made in the natural world based on fitness but by human selection based upon 'looks' or the need for specific traits. It seems in the natural world there is an analogous situation, that of 'sexual selection'. In many species, there is also a tendency to choose one's mate based on their 'looks', which might mean anything from shiny coat or bright plumage to 'dancing' ability. One can make up any number of 'Just So' stories to explain why this is the case, and it may well be that fitness and overall health can be expressed by those traits, but it could also be purely accidental - some just prefer blonds...
An animal species is generally defined as a group of which can not (or does not) interbreed with another. As groups of animals diverge to exploit the part of the ecosystem which best suits them, they may still come into contact and interbreed, such as is the case with wolves and coyotes, but they only seem to do so if the environment is highly disturbed (as happened in North America). Groups which do not interbreed frequently will at some point accumulate enough mutations to the point where viable offspring can not be produced, even if they mate; for example, horses and donkeys can mate to produce a mule, but the mule is sterile, so mules are not a self-sustaining species. All animals live in the blowtorch of time, which continuously melts and twists them into new shapes, better suited to survive in ever-changing circumstances. If such change were not possible, very few living things would exist.
My tendency is to go with the least complicated explanation, which is that of the materialists, although the possibility of some transcendent ‘designer’, YHWH or the alien student, can never be disproved. This view is simplest in that it does not require the addition of yet another force to our universe. I acknowledge the ID people’s issues where they cannot see how many of these evolutionary steps could have come about, but absence of knowledge is not the same as impossibility. After all, most of our modern world would have seemed impossible only a few years ago, and having a working radio a few centuries ago would be proof certain of witchcraft.
I think the issue the ID group has with evolution is virtually identical to that of the Creationists; evolution of man from a primitive organism by purely material means is felt by them to deny a ‘special place’ for humans in the scheme of things and deny us a ‘Reason For Being’. If we just got here by a series of stochastic events and the slow drift of organic chemicals, then what is the point of it all? My view is that since there is not a provable ‘Reason’, it frees me to find my own. If others want a more Cosmic Reason, one might believe we were put here to free the trapped carbon from the earth’s crust and prevent the low-carbon-dioxide death that the earth’s biome faced during the last Ice Age. Since we are doing such a good job at it, who can argue that we weren’t specifically put here for that purpose?