Bees are opportunists when it comes to their homes. They live in horizontal and vertical arrangements with equal ease. I don't see that either is more natural. I've found bees in limbs and trunks. I've found them in walls and floor joists. You could argue that adding boxes to the top is less natural than adding them to the bottom, but adding them to the bottom is a lot of work and I don't think it matters that much.
Just catching up with a few interesting posts ...
I agree absolutely - also with Robo's comment about confusing primitive with being "more natural".
I wouldn't want to argue this to the Nth degree, but I think box
volume is a much better indicator of being "more natural" than box orientation. Because - in the smaller beehives people used in the past (meaning roughly the pre-Langstroth period), swarming was more-or-less inevitable - indeed it was actively encouraged by many in order to multiply the number of colonies a person possessed.
In contrast, today's adoption of much larger beehives and our pre-occupation with the prevention of swarming could well be described as being "unnatural" practices.
That's not to say I approve of letting bees swarm - quite the opposite. I guess that make me an 'unnatural' beekeeper.
LJ