Please explain this effect to me

[defconfunk]

The image below was taken on my Canon AE-1 with kit 50mm F1.8 lens.
The ride is in focus, and right around him the boken is swirly, almost like a radial blur has been applied.

I normally associate that swirling with much older lenses, and haven't noticed it before on any shots from that lens. Also, the edges of the picture, which are really far away, are in focus.
What would cause that?

 

[nikon_sam]

Most likely caused by heat coming off the motorcycle's engine...it looks like the motorcycle isn't moving so the heat vapor is just going up...
http://500px.com/photo/6232667
I found a photo that shows this on another site...click on the link to see it...

 

[defconfunk]

Ah, that makes a lot of sense. I ride a motorcycle, so I'm well aquainted with the engine heat - I just never thought of it. Thanks!

 

[dogberryjr]

It looks to me that the concrete wall is more in focus than the rider, and the swirliest of the bokeh occurs in the crook between the rider's face and arm; that area of foliage is at a different distance than the foliage behind the rider.

 

[defconfunk]

You are right, the wall is better focused than the ride. My camera seems to focus slightly behind where the split-prism says it should - I don't know why that is. If anyone can help me get that sorted I'd appreciate it too!

The foliage directly behind the riders is inline with the foliage on either side of him. The building at the far right is several times further away.