LOL...yea if I seem like Im just coming out of a foxhole in a battle,its because Im more used to dealing with the green anarchist crowd on this subject.Unlike the hunter gatherers of old,these ideological ones are much more aggressive.Lets not forget Zerzans projects before GA like Black Clad Messenger.
That aside,I totally agree that the land defines the approach.Thats why,IMO,some areas just lent themselves to horticulture and semi sedentism rather than some fall from grace being the cause.
I think the number of species you listed that hunter gatherers ate is a broad generalization.Certainly eskimos didnt have 200 plant species.Other ecosystems(mainly northern)are also not naturally condusive to humans.Here in the PNW we have few edible nuts with hazel being the only exception and that never producing nuts unless full sun/management so the recorded edible species are a lot lower.Hence the development of horticulture.As you pointed out-the land defines the approach.Natives on the coast were less oriented toward management but here deep in the North Cascades,the natives were known for their land management.Areas less condusive to human existance required more effort.
My indigenous references come from personal interactions but also from a great book called 'Keeping it Living' by Nancy Turner.In it she lays down her case for why the indigenous peoples here felt horticulture was their peak and not a transitional phase.Great Book!
While focusing on available diversity(both cultural and genetic)may seem reductionist,I have a hard time viewing it as any more reductionist than focusing in on hierarchy and egalitarian power relations.I get that many end up in these discusions through their own anarchist philosophical journeys and admitedly,I also was originaly drawn in by that but I also was into gardening so ended up on the horticultural end.At one point I had over 1000 edible plant species collected but yes diminishing returns left me happy to settle on 100 for my basic needs.The difference is that I got to chose which ones.Unlike hunter gatherers,I actually got some say in what flavours would make up my existance.That freedom of choice is one of the virtues of the horticultural reality.I would encourage folks who think hunter gatherer is ideal to try it out.I found that I didnt particularly like all the species I would have been forced to consume to maintain that ideal.Like I said earlier,I like some of the advancements in flavour that breeding has brought us.Sure,there are some nutritional losses in the process but I figure Im probably healthier if Im actually excited to eat something because it tastes good rather than marginalized into consuming it.This coming from someone who was as hard core of an ideological eater as they come!
I should also mention an experience that had a profound experience on me.For many years I collected native fruit for seed.I would only collect edible fruit because that was the only ones interesting to me.Some years I collected over 1000lbs of fruit.I had to keep track of how many pounds I was picking per hour to ensure that it was worth my time.For various reasons the old growth forests were the least productive.Managed areas like under power lines were the most.It really impressed upon me how management,perhaps as simple as burning could drasticaly improve yields.Simplification of the ecosystem taken too far becomes agriculture but in the right balance can make life in this ecosystem much easier.
The zone approach,IMO, plays into the liniar path world view.I like to view horticulture as the third way.Between the extremes lies the path.In that vien,I cant help but wonder to what extent the recent trend toward paleo is just reaction to industrial civilization as that has been a factor in my own interest.As in zone 1 is really bad so zone 5 must be really good.Or perhaps Im reading the whole paleo application wrong and the goals here are just to take the things we like from hunter gatherer life and apply them to modern existence.Like crossfit excersize and grass fed beef in which case horticultural might be a more accurate description of taking advantage of both worlds.