I was curious if anyone knew off hand. I mean I know there are those on the forum that have even deviated from that range, but in general. Where did we aquire the cookie cutter 80-92 degree heat gradient from? Did someone measure African temps and figure this was good, or was it random trial and error and someone found this worked well? Was it in an old book with no source (be surprised how many truths originate from this)? what made this the most recommended standard?