> The thesis of Guns, Germs, and Steel was Europe's east-west orientation allowed varieties domesticated in one place to easily grow in another.

It's worth noting that despite the east-west orientation of Eurasia, there is quite little evidence of technology and agriculture actually being shared between the Mediterranean and Chinese origins, especially if you restrict yourself to the traditional origin-of-civilization innovations such as agriculture itself, pottery, metallurgy. By contrast, the Americas show a great deal more transmission along its north-south axis, with maize (from Mesoamerica) almost completely supplanting native North American domesticants, pottery appearing to come from the Amazon rainforest, and metallurgy arriving from the Andes.

Didn't a lot of things from Asia come to the Mediterranean to become omnipresent things? E.g. oranges, lemons, rice.

Isn't wheat itself something that spread both ways from the middle East?

Wheat, barley, lentils, peas, chickpeas.

Goats, sheep, pig...

Most of those come from the fertile crescent.

For all intents and purposes, I equate the Fertile Crescent with the Mediterranean world. The big divide I'm talking about is crossing from China across the variety of deserts to reach Mesopotamia and the Mediterranean.

> there is quite little evidence of technology and agriculture actually being shared between the Mediterranean and Chinese origins

You mean apart from (just off the top of my head) gunpowder, paper, the Hindu-Arabic numeral system, stirrups, and pasta/noodles?

> If different varieties of potatoes grow differently at different latitudes (I don't know, I'm not an expert), then it doesn't really matter how productive a crop the potato is.

The introduction of the potato reshaped Europe and boosted European population by 25%. https://www.youtube.com/watch?v=xROmDsULcLE

> The Inca didn't have horses, only llamas. Horses were militarily very important.

The horse is a valuable animal given a favorable terrain. But with elevations such as the Andes, a horse is not as useful. And wheels are a similar story.

Horses were useless in the Battle of Ollantaytambo, where the Inca used terraces to their advantage, but proved very useful in the defense of Lima (a coastal city) against the forces of general Quizquiz.

> After initially being defeated, acquiring guns, steel, and horses from the Spanish and then rebelling against them.[1]

The Mapuche did not "acquire" guns or steel. They could not manufacture them, but they became aware of them and developed techniques against them.

They knew harquebuses were not waterproof, and if they would prefer to engage during rainy weather. They knew that trying to pierce through steel was ineffective, so they prefered to stun.

They also became aware of the usage of cattle and they frequently raided cattle and set structures on fire.

> The introduction of the potato reshaped Europe and boosted European population by 25%.

I think you missed the parent’s explicit point or I missed your point. The parent wasn’t saying potatoes aren’t efficient; only that they didn’t spread widely throughout the new world due to geographic factors.

As for the rest of your post, I’m really not sure what point you’re making by focusing on the Inca. Specifically what about Diamond’s thesis are you refuting? Note that I’m not partial to “Guns, Germs, and Steel”; I just want to understand the criticism better.

The GP simply made a mistake. Potatoes can't grow in hot equatorial climates and never made the jump to the north. Two more American crops are essentially as productive as potatoes and did spread widely before Europeans. Sweet potatoes were grown as far north as Mexico / the Gulf and Maize was growing from Canada down all the way through Argentina.

Potatoes were not a panamerican crop, but they were grown in Spain and the British Isles as soon as they were introduced.

The Inca had a population of 10,000,000, and warehouses with surplus food that could sustain the empire for over 10 years.

I think this is consistent with Diamond’s thesis—the New World didn’t have “guns, germs, and steel” because important developments (like potato agriculture) remained localized. But again, it’s not clear to me if your goal is to criticize Diamond’s thesis or not.