I went to an archeological dig yesterday. It was tiring, but helpful. I’ve been having trouble with my research because people tend to feed me bits of information rather than the raw data I want – I find anything but raw data hard to swallow. As a result of that trip, I was finally able to wrap my head around one issue in this debate: the fossil record as evidence for Evolution.
The case of the Footprints
Note: This example assumes that we do not get into the size of the footprint. Many people have the same size foot anyway.
To see this, picture yourself walking on a sandy beach. You’ll leave a trail of footprints behind you for as long as you walk. Someone else coming upon this trail will find themselves thinking that a human being must have walked from point A to point B leaving that trail.
Notice that this uses inductive reasoning. The person knows (1) That human beings can leave such a trail and (2) That human beings often leave trails like that. As a result, the explanation is possible and plausible. The person then concludes that this is the best explanation. It is possible that this explanation is wrong – possible, but not likely. Unlike deductive reasoning, one can’t be absolutely certain, but they can be pretty darn sure.
Now, imagine that there are more people on the beach. They throw balls, set up umbrellas and picnic cloths and play all sorts of games. In the process, they destroy some of your footprints – just a few here and there. Looking at the footprints, you can still be pretty sure that they were made by one person walking from point A to B. But as more footprints are destroyed, your certainty should decrease. What should make you think that a footprint here and there were made by one person walking from one place to another?
Imagine then that a big wave comes and washes away all but the very 1st and last footprints. Imagine also, that these footprints were 30 feet apart. If you told someone that the footprints were made by one person out for a walk as the person walked from point A to B, why should the person believe you? They should respond with incredulity. It’s possible, but given the vast number of people who come to that beach, how plausible is it? And even if it were plausible, what evidence do you have for its truth?
In this post, I’m going to argue two points.
1. That the existence of an a pretty continuous fossil record, like an almost complete set of footprints, is good evidence for Evolution.
2. That the less continuous such a record is, the less reliable it is as evidence.
Beyond Reasonable Doubt
There are those who do not regard the fossil record as evidence for evolution. As they say, cars today look like but are more complex than cars in previous years, but they didn’t evolve. They were designed. Someone had an idea and numerous people have built on that idea over the years.
Those who say so have a good point. The existence for similarities between things that existed in successive time period does not necessarily imply evolution in the biological sense (the neo-darwinian theory of mutation and natural selection). But it does suggest evolution. It is simply the mechanism of the evolution that changes. The mechanism in this case is intelligent beings. Some people built the first car and humans kept adding a little to it, one at a time, till we got where we are today. Every new car after the first used some of the ideas already actualized. They did not start from scratch.
A set of footprints on a beach and the knowledge of a path* by which they could be formed by one individual do not constitute evidence beyond all doubt that the footprints were made by one person. But they do constitute evidence beyond reasonable doubt. A set of cars showing the change in cars from their first creation till now, and the knowledge that humans can use previous ideas to evolve the idea of a car (i.e. create cars that are similar to older models, but still different) do not constitute evidence beyond all doubt that the cars were made in such an evolutionary manner. But they do constitute evidence compelling evidence in the absence of good evidence to the contrary. Likewise, a progression in time from less complex to more complex living things and a mechanism by which changes can be made to species to transform them into other species does constitute evidence for evolution in the absence of evidence to the contrary.
Notice that I have laid out two basic requirements (there might be more):
1. The presence of a pretty good progression from less complex to more complex.
2. The presence of a mechanism by which the evolution can be carried out.
Mugs sort of look like plastic cups, but they can’t evolve from each other. So no matter how much alike they might look, they didn’t evolve. They were made for similar purposes and that purpose has certain requirements (to be solid, waterproof and have a hollow, for example). That’s why they look alike. On the other hand, airplanes could have evolved from bicycles. The mechanism (humans with creative ability) is present. But there’s no progression that we (well, I) know of.
How Continuous should the record be?
Think back to my footprint illustration. The reason we know someone walked from point A to B is that we can see a good progression. However, in the last photograph, we can’t make that conclusion. We just don’t have enough evidence so making such an argument would require great imagination. The progression is only good evidence as much as it is a progression. Two footprints 30 feet apart is not a progression. Two adult footprints 30 feet apart and a few child’s footprints in between is also not a progression. That’s why people talk about the ‘gaps’ and ‘inconsistencies’ in the fossil record and talk about how ‘complete’ the fossil record is. There is no magic number at which a gap becomes too large. What some people find convincing, others won’t. We’ll never get a complete fossil record, so the question is: how good does it have to be in order to make Evolution beyond reasonable doubt? That’s like the question: how wide a pit is too wide to jump across? 30 feet is too wide for everyone and 2 inches is really small. But somewhere in the middle, the answer isn’t the same for everyone.
Still, when I am told that the fossil record is ‘overwhelming evidence’ for Evolution, I can’t help but think that these people mean that the fossil record is almost complete. I haven’t seen the fossil record, but can that many Frenchmen be wrong? I’ll let Alex Rosenberg tell me.
What would disprove Evolution?
Besides the second coming? I haven’t thought about that very much. There is room for attack on it, however. A very bad fossil record and the absence of a path* should force one to relegate it to the status of a hypothesis, but as for disproving it, we can’t make an argument from silence. We’ll need evidence that it is false.
*I explain what I mean by a path in Why Evolution Needs Mutations
Now, as if you needed pictures: