Where did evolution start? Where did that first tiny self-replicating particle come from? This is the third in a three-part blog (see part 1 and part 2).
One of the oft-used arguments against evolution is that, even if the Earth is 4.5 billion years old, there wasn't enough time for life to start, much less to evolve to its present state. But most people who assert this have no idea what 4.5 billion really means.
Here's a fact: If you had a billion dollars on the day Jesus was born, and you spent $1000 every day since then, you'd still have $266,000,000 left today.
Most people understand that Jesus was born a long time ago, but somehow the idea of "two thousand years" is not that different in their minds from "four billion years." But the idea of spending $1000 each day for two thousand years, and still not getting to one billion puts it into perspective. Four billion years is two million times longer than the time since Jesus was born.
And that's the problem with understanding evolution: Most people just can't grasp the scale, not even within a factor of ten or a hundred, of what "four billion" means.
Innumeracy, our inability to truly grasp large numbers, is a surprisingly high barrier to widespread acceptance of evolution. The evolution of the human mind did not include any necessity for understanding concepts like thousand, million, or billion. Even scientists, engineers and economists who work with these terms daily only understand them in the abstract mathematical sense, not in an intuitive way.
But it's even worse than that, because the human mind is also innumerate when it comes to sizes. When we think of evolution, we thing of animals, plants, maybe insects and fish, and finally down to the scale of bacteria. But most people have no idea just how small a bacterium is compared to the plants and animals they see every day.
A single bacterium from the gut of an elephant is (very roughly) 1,000,000,000,000,000,000 (1018) times smaller than the elephant. Consider the population of Earth at six billion people: If each person were the size of a bacterium, it would take over 1.6 million Earths for the people to equal one elephant. To a bacterium, a small pond of muddy water is a virtual universe, one that could hold billions, trillions and more, bacteria. Most people can't grasp just how many billions of cubic meters of rock, water, beach sand, and other places exist here on Earth where life might have originated.
Compared to the human lifespan, or even all of human history, the dimensions of both time and space available to evolution on Earth are unimaginably large. This is what "innumeracy" means: We're not capable of understanding these numbers intuitively, It's our intuition that gives us common sense, yet anyone who applies common sense to the timescales of evolution simply comes up with the wrong answer.
We started this series of blogs with the question, Where did evolution all start? I've attempted to answer this with three points: First, just because we don't have a final answer to any scientific question doesn't mean we won't someday, and falling back to magical explanations is wrong. Second, a lot of good science has shown that there are possible answers to the origin of life. And third, common sense leads many people astray when evaluating the evidence, because the timescale and physical dimensions in which life originated are beyond human intuition.