> What makes you think those plants aren't more genetically complex and developed than we are? A lot of our complexity is non-genetic.

The real problem is that "complexity" and "development" in the context of evolution aren't well-defined. So the way that they place genomes on the x-axis is really arbitrary.

> You mean exponential growth, not an exponential distribution, and exponential growth never hits the x-axis.

Right, exponential growth. And yeah, the horizontal line that they're extrapolating back to isn't the x-axis, it's the y=1 line. The point remains: roughly speaking, it seems like small changes to the curve could produce large changes to the x-coord where y=1, since the curve is so close to horizontal there (on a linear-linear plot), right?