I really dislike this example because the underlying metric is so poor.

It's not the least bit surprising for 2% to make such a large difference. We deal with this sort of thing on a highly regular basis -- ordering food at a restaurant, writing code, reading books, having conversations...

The 2% example says the obvious: "Aliens could be really advanced compared to humans because they're different from humans in a way that makes them really advanced."

We may have a genome that is only two percent different from that of a primate, but the result is nothing short of a singularity. Chimpanzees may be amazingly advanced mammals, with complex social systems and the ability to use sticks as limited tools, but... Our two percentage points gave us Shakespeare, the Italian Renaissance, jazz, the wheel, skyscrapers, the Apollo Program, agriculture, global telecommunications networks, gunpowder, the Cold War...

Even an alien civilization that may seem like gods to us won't confuse us with our genomic neighbors.

What does DNA have to do with it?

The point is that our next relatives on the tree of life are very similar to us in many ways but we would nevertheless consider them pretty stupid. Pretty much all impressive human achievements will be forever inaccessible to them. DNA is just a very striking way of illustrating that similarity with the one big difference.

It is similarly imaginable that evolution could, without breaking a sweat, spit out intelligence that would consider us stupid the same way we consider chimpanzees stupid. They can do some cute tricks but that’s about it.

He basically wants to open our eyes to the idea of a vast scale of intelligence, not between village idiot and Einstein but spanning much wider. Meeting someone that is just as intelligent as we are seems unlikely.

I understood what he meant, I just didn't understand why DNA was helpful in illustrating it. I'm a lot smarter than a nematode, or a pebble, or a cell in Conway's Game of Life. The number of base pairs I share with any of those things (where applicable) is irrelevant.

That's a 60MB difference in a 3GB text file. The message could be wildly different...