Firefox Quicksearches + Google Keywords = Sick Power

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.

evidence

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?