There are millions of mineral and rock formations around the world with 90 degree angles. A tree/flower stem/etc and the ground form a 90 degree angle. A branch coming straight out of a tree trunk (common in pines, or some other evergreen) makes a right angle. A vine or spanish moss dangling from a branch makes a right angle. Two logs or branches that fall on each other in the forest serendipitously form a right angle. An arm, leg, etc sticking out of an animal with arms forms a right angle when extended. Water running down from two different points on a hill toward a central point could easily join as a right angle.

I'm pretty sure right angles existed before this log.

e.g. https://en.wikipedia.org/wiki/Halite#/media/File:Halite-2493... ("Halite cubes from the Stassfurt Potash Deposit")

They're normal.

When our first ancestor stood upright, a right angle was formed with the ground.

A hand axe, a knapped stone lashed at right angles to a branch.

Some say fire or dogs are humanity's first and greatest inventions - but we only domesticated those.

I say weaving: an extraordinary crossing of threads at right angles that magically support each other, clothing that is the biblical coming-or-age of human-kind, fabric that drapes organically (and is still used today, even as threads become artificial), rope, leaves for shelter, even decorating hair.

And it directly lead to the single greatest invention of our time, that binds all things together: gaffer tape.

Naturally occuring cubic crystal systems might beat it by a few million years wouldn't they?

plants frequently come out of the ground and go straight up. things fall straight down, which is why bipedal humans stand straight up. our bilateral symmetry (arms out!) is at right angles to our bifocal vision, and we have people to our right and to our left. birds' beaks and dogs' muzzles are a vector notation from their bodies. various types of axeheads affixed to axehandles... I'm not saying the discovery is not amazing, nor that you're wrong, this could be the first. Just saying that right angles are going to come pretty quickly after the discovery of angles.

Surely stone tools have demonstrated perpendicular attributes. It’s not too far of a stretch to imagine a Palaeolithic hunter aligning an axe head against a handle in a way that made it even on either side.

I haven't seen any stone tools with perpendicular sides. In fact, I don't know of any other 90-degree stonework until the T-stones at Gobekle Tepe. If you could point me to some examples I'd be very much interested in knowing about them.

Just arrange two branches in a bonfire. Most humans will tend to create a 90 degree angle.

As any other animals, we are brain wired to recognize symmetry. Is our main way to find a desirable mate with good genetics or to detect a predator ambushed so is essential in our survival.

Not sure how you can surmise that. The earliest human-made tools are from 2.6 million years ago. You think nothing starting from then to this wood house had a deliberately constructed right angle?

Bismuth!