Here's an interesting thought I had. So,a common visual on DMT is either machine entities or massive multidimensional machinery, oftentimes with moving parts not dissimilar to gears or cogs; things that look like something from a steampunk fantasy. But use of Ayahuasca and therefore DMT dates back to before the industrial revolution, perhaps long before it. So some of the things that these visions resemble didn't exist in that form or caliber yet. You could chalk it up to our own cognitive ideas of machines built by our modern society, but it's such a consistent experience on DMT that it makes you wonder....were indigenous people seeing these kinds of "machines" and if so, could DMT have predicted the future? It's something to consider.

Who knows. I'd bet on it though.

Biology is machine like. Or, more accurately, machines are a like biology (but even less complex)

You probably wouldn't say you saw a machine in the exact same sense as machines in our reality, you're more likely you saw 'something like a machine'.

They may have seen similar visuals but viewed through their cultural lens may have interpreted them to the closest similar thing 'something like a x but...'.

I was going to say that given the mechanic nature of the visuals, they might say 'it looks like a wheel but...'. Then I remembered that some people think the story of Ezekiel in the bible is a psychedelic trip - and he reported seeing a 'wheel in the middle of a wheel', so that could give a clue of how it might be interpreted.

If you're interested in this line of thinking, Carl Sagan wrote a book in the 90s called 'The Demon-haunted world' in part of it he theorises that in modern times, UFOs and aliens have come to replace angels and demons as being a predominant explanation for the same range of natural phenonmena. It also to mind when I read your post.

Never saw machines on Ayahuasca. That's a DMT thing. The Amazonians were not extracting the single molecule and smoking it.

I've definitely seen something similar to turning gears on my first ayahuasca trip

I think our brain generate an interface to visualize the work of Ayahuasca.
This interface depends of our beliefs.
That's why some people, even in deep Amazonian forest see modern doctor taking care if them in place looking like modern hospital.
I'd have an experience with Peganum and Shroom. I was alone and asked to be heal for a disease to one leg.
Suddenly I saw a flying saucer coming, I saw it eyes open, the first time that happened to me.
It was around 30 or 40 cetimerers of diameters. Was looking like in the old movies, not as I would imagine high tech spatialship. I could see through the round windows little men, wearing gray aviator suits and squared sunglasses.
They went out of the saucer to heal my leg.
At one point, I've asked them to let me see they're real shape, and instantly they shape change from men to little rainbows snakes of a vibrant colours full of kindness instead of non smiling little men.
As soon as I could I've googled "rainbow snake" and found occurences mostly in Australian aborigines vision and also in Ayahuasca vision, but not linked especially with healing.
If someone had the same kind of experience, I'd be curious to know.

When I smoke DMT from Acacia Confusa, there is some NMT in it, so I see everything from wavy cartoon morphing visuals to spatial, almost single color backgrounds. I do not remember seeing machine-like visuals or entities when I have vaped. Very fantastical, cartoonish, organic, or artistic. So depending on the person and the kind of DMT, I don't think everyone sees machines.

Could they have seen street signs?

To recognize an object as a class of thing, like a machine, requires familiarity with it.
Moreover the identification of such an object by the brain is a conditional operation that relies upon previously made associations.

In this the concept of machine is a projection applied to a perception and not an inherent property of the perceived. The locations of the perceived and that which perceives in relation to one another can also be considered here.

The minds of those who experienced ayahuasca prior to the industrial revolution performed the same referential associative operations that modern users perform, only the concept of machine was not present in their experience and so could not have been identified.

By substituting the projected concept "machine" with "street sign" another class of modern objects largely unknown in the ancient world, the subjective nature of the question can be explored.

Or rather these are my thoughts upon it.