Perhaps we need Theseus to help with this one.

[en.wikipedia.org]

When it has orange hair and runs for president?

When they vote Republican.

I think it's going to take some time before we ever get to that point. Most likely not in our lifetime. Meanwhile, just keep watching how things evolve.

When they don't ask this question any more.

Also let's not forget the creation factor. Any creation of a human would be part human in a fundamental way. Even if we could assemble life and DNA like Legos to create something, it would not exist if not for us. So human in any creation of man is a spectrum that is in the eye of the beholder. Take a cave man, let him see a man in the 1800s with false teeth, a hook hand, a peg leg, and he sees something less than human to him. Now imagine that same peg leg man seeing someone today. That can run without legs, his arms hooked up to his brain so he can move the hands, his eyes with inbeded lenses for better vision, and implants so he can hear. Peg leg would think this man wasn't human. It's all perspective.

So many ways to go about answering that question! Here are three random musings, each in a different direction.

Possibility #1: If it starts as human, it can't ever become not human. A person in a coma would not necessarily have all of the aspects of free-will or consciousness, but is still human. An enhanced human is still human, assuming free-will and consciousness still exist. This would exclude "computer copies" of brains (a.k.a. "uploads" ), but include those who slowly replaced parts of themselves (including brain parts), in a way that preserved free-will, consciousness, or the perception of being. (so, apparently there is an inherent opinion about the Theseus idea in this answer).

Possibility #2: If it has free-will or consciousness, it deserves all the considerations afforded a human, irrespective of whether it is human. In this light, it seems to me that the question's use of "human" sounds like a category that is superior or preferable to non-human... in which case I'd posit that its use may be hearkening back to religious teachings! (thus a red flag is raised about the dubiousness of the concept). While I do admit that we might have an affinity for our own kind, given Possibility #2, I'd say that you'd be hard pressed to not logically group humans with dogs, cats, orangutans, and all the other entities that possess some sort of brain, no matter how minuscule. Thus it's inconsequential of when you stop being human.
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Possibility #3: As soon as the first upgrade happens. Uncle Bob isn't human anymore...he has a pacemaker. : )

When they (it) become part of the collective?

At the point said human decides it’s something else.

Human augmentation is the next step in our evolution and it's already started with simple seeing eye glasses to very complicated hearing aids. Prosthetic limbs that move on command when you think are getting more and more advanced, soon perhaps we could augment a human brain into a box idk but as long as what ever machinery has a human brain I'd consider it human.

When people begin to identify with the technology and see it as part of them.

I'll let you know if I ever get to that point.

I suggest that, aside from the Theseus paradox, humans are in a continual state of evolution, thus whatever humans become in terms of their makeup and form, they will remain humans. The Theseus idea looks at a single object (Theseus ship) being reworked over time, so it deals with an object. When we talk about humans changing over time we are not considering whether or not a single object having all its parts replaced over time is the same object. We are talking about a class of objects (humans) changing over time. They are two different ideas.

I think it will be when it no longer can reproduce another human. Like all species we evolve and when we can no longer reproduce with the former we become a new species.

Hmmm... I feel like I'm watching the Star Trek Next Generation episode, "The Measure of a Man." It may feel clunky if you watch it now, but it sets out this argument very well. It applies. Is Data a sentient being or a toaster? The direction the script took was that if start treating "machines" as they become more "human" as not-human, we are re-imagining slavery. I kind of like the cheesy ruling of the judge:

"It sits there looking at me; and I don't know what it is. This case has dealt with metaphysics - with questions best left to saints and philosophers. I am neither competent nor qualified to answer those. But I've got to make a ruling, to try to speak to the future. Is Data a machine? Yes. Is he the property of Starfleet? No. We have all been dancing around the basic issue: does Data have a soul? I don't know that he has. I don't know that I have. But I have got to give him the freedom to explore that question himself. It is the ruling of this court that Lieutenant Commander Data has the freedom to choose."

Now you know what a big dork I am.

Is this a similar question to the axe riddle? If you buy an axe and replace the handle and the head over the years is it still the same axe?

never. you can't escape your ancestry. We're still apes.

people can live with artificial limbs and organs but those organs do not at this point include brains. i think the brain would be the dealbreaker.

g

This is my second post on this thread...but... I just happened across Ray Kurzweil giving his answer to nearly this exact question! He is pretty much the quintessential, if not original transhumanist... His succinctly worded answer is given in the last 3min 30sec of this 1.5hr interview. It's perfect.

[lifeboat.com]

My first thought is that as logn s the brain functions without impairment... but that woudl mean most religous people are no longer human.... Hmmm, this will require more thought.

When we lose what makes us human: our humanity. Empathy. Compassion.