How Would *You* Prove Evolution?

I need some help here. I have a friend with whom I’m debating evolution. He is a fundamentalist Christian (wait for it), but he has an uncharacteristic understanding of, and respect for, science.

So he’s an extremely intelligent guy who doesn’t deny the validity of science. In fact, he actually accepts microevolution. He’s familiar with the various moth studies and such, and accepts them as solid. What he disputes is the concept of macroevolution. For those not up on the terms, macroevolution is any evolution that occurs at or above the species level, meaning that over time the offspring species would become unable to mate with the parent species.

But Rick’s main argument concerns less subtle differences. He doesn’t care if moth A becomes moth B, and that after many generations they won’t be able to procreate with each other. He wants more than that. He quite simple rejects the notion of all life having a common ancestor.

So here’s the problem: his argument is that he and I both have beliefs; I believe in macroevolution and he believes in God. When I show him that my beliefs (and not his) are backed by empirical evidence, he refutes the evidence using assorted websites that dispute various parts of the findings. After this happened for like the third time I realized something.

If I cannot explain macroevolution to him — or anyone else — that means I don’t totally understand it myself. And if I believe it without understanding it then it IS a belief. So on that point he’s absolutely correct.

All that remains is me thinking that my belief is based on more evidence than his belief, and that’s where the evidence comes in. Hence a never ending cycle simply because I don’t understand the science well enough myself to articulate and defend it.

So that raises the question in the title of this post: how would YOU explain macroevolution to someone who believes in science but simply doesn’t believe there is enough evidence to support it? Is it possible to do without learning a whole lot of biology yourself?