Col’s Rational World

What is evidence?

I’ve heard lots of people claim that those who accept Darwin’s theory of Evolution (or its modern descendants) are just following their own ‘beliefs’ or ‘religion’ because, as the argument goes, Scientists have no actual evidence for what they claim.  This always bemused me because Evolution is probably about the most strongly supported theory in all of biology, with mountains of evidence so high that no one human could ever be aware of it all.

I think the difference of opinion comes down to the definition of evidence: creationists seem to think that the only acceptable evidence of a scientific theory would be if you could actually watch the whole process in action.  Well, we can certainly watch the evolutionary process work on simple organism like viruses and bacteria that have a lifespan measured in hours.  Fortunately, the results from such studies agree perfectly with what the theory suggests. But of course we can’t watch evolution running from the primeval Earth right through to the modern day; I don’t think the government will fund research salaries for four billion years.

So, is the creationists’ definition of evidence a sensible one?  Well no, of course it isn’t.  Let me give you an example of a situation to explain my point.  Imagine, if you will, that you were sitting ona jury in a criminal court.  The defendant stands accused of first degree murder, having allegedly killed his business partner in cold blood. The counsel for the prosecution has just presented ten credible witnesses, all of whom saw the defendant walk into the house where the murder took place, they heard a loud scream, and saw the defendant run out covered in blood. They saw him drop a knife in bushes nearby, and that knife was later recovered by forensic detectives and found to be covered with blood of the victim and fingerprints of the defendant.  Nine of the ten could identify the defendant in a line-up. The knife was proven to be the murder weapon by further analysis. The crime scene was covered with DNA evidence straight from the defendant including a handful of his hair that had been pulled out by the victim, apparently in a struggle, and which remained in the victim’s fist.  The defendant was also heard by seventeen further witnesses the day before to say “I’m gonna kill him.  I’ll stab him with a knife.”  The victim had, apparently, stolen the defendant’s money and had an affair with his wife.  Shortly after arriving home, the intelligence services (who had been monitoring him as part of an investigation into his shady business deals) recorded the defendant on the phone telling his closest friend that their problems were over and the victim wouldn’t be bothering them again.  In addition to all of this, CCTV footage of the streets outside the building caught the defendant entering and leaving, exactly as the witnesses said, and followed him in an unbroken chain of video all the way back to his house.

That sounds like a straightforward case of ‘guilty as charged’, but at this point, the defence lawyer stands up and says “Your Honour, I move that this case be dismissed because the prosecution has failed to present any evidence.”  Amidst gasps of disbelief, he continues, “Not one single witness actually saw my client stab the victim with the alleged murder weapon. All the prosecution has presented is their religious beliefs about my client’s alleged guilt, and I’m afraid that’s not enough for me becaause I believe differently. My client has told me that he was innocent and that’s good enough for me.  I have a deep feeling that he is telling me the truth.”

What would you say to anyone so utterly devoid of rational thought?  This is the exact same situation that scientists face every day when faced by pseudoscientists like creationists, and many other species of conspiracy theorist.  Within Science, a vast amount of evidence from a wide range of totally unrelated disciplines, all points conclusively to the undeniable conclusion that Darwinian Evolution is true beyond a shadow of a doubt. Anyone who tells you otherwise is either ignorant, brainwashed, lying or unbelievably stupid. And yes, those really are the only possibilities.

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