I’m about to summarise in the briefest terms just a little of the evidence that supports evolution. But this little post will in no way do the topic justice. For a much more comprehensive explanation of the evidence for evolution I strongly recommend Richard Dawkins’ excellent book:
The greatest show on earth – the evidence for evolution
The evidence comes from several different scientific disciplines, all of which compliment each other (an amazing convergence which is itself strong evidence for evolution). But let’s start at the beginning.
Geological strata and other measuring chronologies
There are many ways that we can measure the age of a particular artefact. For example….
We can use ‘dendrochronology’ (the science of counting tree rings – yes I kid you not) to determine the age of a particular piece of wood;
We can use radioactive clocks that variously measure timescales from milliseconds to millennia to detect the age of certain types of rocks or other organic materials (IE radiocarbon dating – AKA carbon 14 dating);
Geological sequencing: Because we know the relative ages of different strata the world over we can tell during which epoch a fossil was laid down by looking at the rock strata it is found in.
Biology and DNA
We can use biological clocks (EG variations in DNA between species) to measure the length of time between the evolution of species.
Carbon 14 dating (mentioned above) is a kind of biological clock because it measures the rate of decay and therefore the age of Carbon 14 in organic matter.
Fossils
By cross-referencing fossil finds with geological strata, radioactive/geological clocks, dendrochronologies and carbon 14 dating it has been possible to build up a record of the earth’s history going back billions of years.
These clocks are remarkably consistent and to deny their accuracy is to assume that no matter how much they complement each other they are all false and the correlations between them is just coincidence, or as some creationists have proposed, just God’s little joke.
But by taking the fossil record as a whole – and it’s much more complete than many would have you believe – it is possible to observe the adaptations and differing speciation, in chronological order, to see just how humans evolved from earlier hominids, mammals, reptiles, fish and crustaceans. It’s true that the fossil record doesn’t extend much beyond that stage because soft-tissued animals like amoeba don’t tend to leave fossils – but DNA, links to more distant evolutionary cousins and even the presence of modern viruses can fill in those gaps.
And don’t worry about ‘the missing link’ – there really isn’t one – just an odd academic way of classifying fossils that makes it look like there is.
Guppies and germs
We can even see evolution happen before our eyes (and the experiments confirmed the falsifiable predictions made – the hypotheses).
For example Richard Lenski and his colleagues at Michigan State University painstakingly bred 45,000 generations of bacteria in the laboratory and watched them evolve, not once – but twice to make use of available food stuffs. This double-whammy adaptation represents what creationists tend to describe as ‘irreducible complexity’ and yet it happened.
Then there are Trinidadian guppies who kindly adapted their markings to fulfil hypothetical predictions when Dr. John Endler changed their environments to introduce different kinds of predators.
Both these experiments demonstrate that evolutionary theory can generate, test and ultimately be confirmed by falsifiable hypotheses in ways that mere dogma and unthinking belief cannot.
Irreducible complexity (eyes and wings)
One of the favourite brickbats thrown at evolution by creationists is the argument of ‘irreducible complexity’. The argument is that since every adaptation needs to represent a viable improvement for the animal that acquires it there are some adaptations that just don’t meet the criteria. There is no benefit in having ‘half an eye’, for example of ‘half a wing’. This is regularly put forward as a logical argument against the theory of evolution by natural selection. There’s just one problem …….
It doesn’t make the slightest bit of sense.
Let’s just look briefly at the two ‘favourites’.
The eye – Creationists assume that something so complex as the eye could never have evolved because the intermediate stages (before the ‘perfect’ eye evolved would be useless. But this is just not true. Even a rudimentary light sensor would be advantageous to a creature that needed to detect movement – which is precisely why some animals have just that – light detectors. The first stage toward evolving an eye. Between them and the sophisticated eye of eagles or other creatures with acute vision are a myriad of intermediaries (including the slightly less acute eyes of human beings).
I put the word ‘perfect’ in inverted commas, by the way because frankly there’s nothing perfect about the human eye at all. It’s back to front and upside down. It has a hole in the retina where the optic nerve passes through it resulting in a blind spot and it’s prone to all sorts of defects from myopia to cataracts. Hardly the work of an ‘intelligent’ designer. Quite frankly Minolta does better (and has done for years).
Similar arguments can be made for wings. A rudimentary flap of skin that assists gliding (even slightly) is better than no wing at all (and some species of tree squirrel have precisely that). There’s nothing ‘irreducible’ about either of these. In fact there’s nothing irreducibly complex about any part of the human body. Some body parts evolved from slightly advantageous prototypes of the ‘final’ form whereas other evolved from organs that were once used for completely different purposes (a process known as exaptation).
Predicted species
But the real proof of the pudding is in the eating. Can evolutionary theory predict species we don’t know about yet based purely upon what we know about the ‘rules’ of natural selection? Well – yes, it can and it has done.
Perhaps the most famous example is the long-proboscis moth ‘Xanthopan morgana praedicta’ (Darwin’s famous ‘Hawk Moth’ ) which Darwin predicted long before it was discovered because it ‘just had to’ exist if natural selection was correct . But there are others – the theory of evolution by means of natural selection allows scientists accurately to predict species and adaptations and has done for years.
All of this evidence, taken from many sources and lines of inquiry matches up. There is almost no way that any incorrect theory could be son consistent across so many different subjects.
This variety of supporting evidence, together with the absence of any contradictory evidence is what makes the theory of evolution so strong. It is, in all but the most scientific circles, a ‘fact’. As proven today as the fact of gravity or nuclear fission and far more plausible than some of our most cutting edge scientific theories such as string theory or the multiverse.
In short, to deny evolution by means of natural selection is to deny the evidence of your own eyes, the findings of generations of rigorous scientific inquirers and the effectiveness of evolution-based developments such as antivirals, gene therapies, HIV treatments and even antibiotics.
Filed under: Critical thinking, Hard wired, Religion, skeptic | Tagged: biology, carbon dating, Darwin, dendrochronology, evolution, fossil record, geology | Leave a Comment »