I watched that same documentary with interest but became frustrated at the end because they never tried to make a connection re what the "rain forest" would have looked like when the Sahara was largely covered with shallow seas. Scouring the web revealed several efforts to make a connection that never made it into "prestigious journals". Not sure what to make of that. Maybe if they blamed humans for draining the Sahara they could have gotten published???
In any case, and just like this guy found, most conclusions were the South American rain forest was savanna type landscape when the Sahara was wetter. It becomes even more interesting when investigating a cause for this "climate change". This of course happened well past the end of the last glaciation??? Whatever. The theories run the gamut from pole shifts to alien terra formers. From most accounts the change was relatively swift, in geologic time.
The scientific community™ is nothing if not frustrating. They apparently go as far as the money and no farther. Maybe journal publishers can share the blame since they are the ones who select studies and research that make the cut? In a publish or perish environment whaddaya gonna do, but I digress...
I have read articles here at FR to the effect that very large deep earthquakes, such as the one that created the Indonesia tsunami, can shift axis and rotation by a tiny bit, less than 1 degree, and ultimately have huge effects on climate.
I could see a large meteor hit doing something like that as well.