Reasonable Dissent

Which came first – the heart or the blood?

I got an email from a reader recently that seemed like a good topic to really get into. Basically the question was this: Consider the human body. If we’re to believe that it evolved from very simplistic life, which evolved first – the blood or the heart?

There are two ways that I can see this argument going. The first is a sort of implied “god of the gaps” argument, where essentially we’re faced with a question that we don’t know the answer to (but in this case, I think we do) and that points us to the conclusion that God is responsible. I’m going to assume that perhaps the person asking did not mean this line of thought, because I don’t think it’s a valid argument. Even if this one isn’t unknown, there are certainly questions for which we don’t know the answer. But a lack of understanding on our part doesn’t imply God’s presence. It merely means that we don’t know, yet. Every age has had its questions, and we’ve developed an increasing understanding of the natural world. Marvel at lightning from the gods has turned into understanding of principles of electricity – lightning rods protect buildings, where a god throwing them would not behave so nicely. This understanding of electricity allows me to type these words right here. I don’t claim that we know everything, and maybe we can’t know everything (but then maybe we couldn’t know that we can’t know everything… and we start to get a little philosophical for this talk). But the point is that people in the past have made the mistake of thinking that there was no other explanation, and it’s just as fallacious today.

The other path that this question could follow is a sort of key idea to intelligent design – irreducible complexity. I don’t claim to know all the ins-and-outs of intelligent design, but from my understanding this is the main idea of irreducible complexity can be thought of like this: Consider that you have a watch.  It has hundreds of working pieces that all fit together very nicely (like the human body). However, if you were to remove even one of these components, the whole thing would fail. It’s said that we can find a point in biological life where you can’t ‘build it up’ from individual pieces because you need all of the pieces to come together and work at once.

One unfortunate problem with irreducible complexity is that it doesn’t stand unless there are examples. It merely says “there exists in nature an irreducibly complex system,” and there’s not a clean way to show this to be false. So, we’re given an example of something irreducibly complex, and even showing why it is not proves only that this example is not valid. Then we wait for the next example. There’s no such thing as a counter example without examining every biological system to some arbitrary detail.

But what choice have we here. It’s the same as saying, “You can’t know that God doesn’t exist because you haven’t looked everywhere he could exist.” Well, fine, but if you give me an example of where you think he might be, I’ll tell you why I don’t agree.

As for the heart/blood question, I think the simplest answer is “the blood”, but only in a vague way because blood has changed too. Most organisms need a way to move things around – nutrients, waste, etc. In especially small organisms, this obviously doesn’t need to be very sophisticated.  Diffusion, where concentrations of a substance tend to find a state of equilibrium within their boundary, could account for a very small organism getting nutrients to all it’s parts, or allowing waste out. But even very simple organisms also have muscle-like functions that serve to move the ‘carrier substance’ (that only vaguely resembles blood) around. As these organisms grow in size, only then does a specialized heart begin to develop, which may not have resembled our 4-chambered heart for thousands of iterations. There has also been some real study of this progression. I have not read this entire article (you’ll need an account if you want to), but the abstract is helpful on its own anyway.  In any case, our vantage point is that our body seems to work exactly right, but this isn’t insightful. It only means that our heart is the one that works for us, right now, where we are. If it didn’t work for us right now, it would have evolved differently, to fit those requirements. And the ones that didn’t would die out or find a different role to fit into some other survival spot.

This also brings up an interesting point that my fiance and I have discussed many times. People often see evolution as some sort of slow march toward a goal, or like the evolution posters show with an ape that slowly morphs into common-day man. It’s a misleading way to think about it, and I think it causes some misconceptions when taken to the simplest interpretation. First, species either survive or they don’t, and the ones that survive happen to continue on their line. But that doesn’t mean that there aren’t species that failed, or that there is a single line of lineage. It’s more like a gigantic tree, with branches here or there, this branch going off and creating many branches of its own, that branch going off and stopping. We may be able to trace back the path that we evolved from to some extent, but that is not the whole story. Second, evolution does not have a goal in mind. It is not the case that you can look at some creature and say that it is 5 million years behind us. That species is evolved to fit its particular spot in the ecosystem. Crocodiles may not be on the path to being able to fly, and dogs may never evolve to talk to us, because that might not have anything to do with their survival, which is all that really matters.

To think of evolution as a straight line from a single cell to some final ‘perfect’ evolved form is incorrect. All species wouldn’t evolve to be the same, because there would be no balance, no niche for each species to survive in. If everything was trying to be the same, there would be that much more competition for survival in that area. And we can’t view evolution with a magnifying glass. It works on large scales, letting the stuff that doesn’t work die off and the stuff that does fit keep going. It only looks like everything fits perfectly because we don’t get to see the countless number of things that didn’t.

Tags: evolution, intelligent design, logical fallacies, science