Human is a fact of DNA — of which embryos are unmistakably humans. But we don’t ascribe rights based on humanity, but on personhood, which is why embryos have virtually none.
You come across as dishonest and put people off from your perspective when you won’t admit basic facts — eg, this is experimenting on humans.
I think perhaps your aversion to basic facts is that you don’t feel comfortable being honest:
You support experimenting on living humans.
Similarly neither are embryos. A human is a collection of trillions of cells arranged in a particular manner, not just any cell (or relatively small set of cells) that has human DNA. Human, as a word, has meaning far beyond that.
I'd agree that personhood is the more important qualification (though, of course, we experiment on people all the time, and rightly so). But a few cells with human DNA does not a human make.
They are absolutely a human.
To sibling comment’s point: personhood versus humanity is already the legal distinction - eg, children and invalids are fully human but not fully people, so we don’t grant them full legal rights and instead let others exercise control over them. For children in particular, we grant them more autonomous control of their rights as they mature.
Your path of denying humans their humanity has a dark history, including within medicine.
I don’t support that, even if they’re very tiny and fragile humans early in their development — eg, if we could raise them in artificial wombs, they may have a right to life as a human, despite what anyone else wishes.
Denying their humanity is denying their right to life as a fellow human.
This is absolutely not the definition of a human. It denies the humanity of genetic chimera (https://en.wikipedia.org/wiki/Human_chimera) and organ transplant donors and recipients. It would define a cancer tumor (which will have it's own unique DNA lineage) as a human.
You're twisting yourself in circles trying to create some pseudoscientific definition of a human based on DNA to get to the outcome when you want, when the definition of a human is simply "matter arranged in a human form". DNA is a tiny portion of that matter, and isn't really critical at all. Theoretically you could simultaneously destroy all the DNA in a human and while they'd die in short order they'd remain human and initially pretty much entirely unchanged (hard to say for how long, maybe hours).
We'll never agree on what a human is [1], but this hamfisted attempt to define it in terms of DNA will never even create a consistent definition with the properties you want.
[1] You're plainly motivated by a spirtual or religious belief in a non-falsifiable manner that embryos share some important spiritual/religious characteristic with humans - likely something to do with a "soul". As a result you want to modify the definition of the common english word human to include them to make your beliefs seem inevitable. Meanwhile I don't share that view and will insist on continuing to use the traditional meaning of the word. I'll die on this hill because it's correct, but also because people who share your view frequently go beyond that and attempt to impose their own religious beliefs on other people in the form of laws that deny them their religious freedom, and freedom to control their own bodies. Laws incidentally that wouldn't be justified even if the embryos were full grown human being somehow squashed inside other people. And laws that have been tried, and result in not just loss of freedom but the death of actual living humans. This is the dark history in medicine that is actually worth considering in this conversation.
There is nothing extra magical about conception that makes the creation of a human (or a person if you prefer that), all of the DNA already existed before and nothing that defines a person is yet present.
My point is that if you feel that way, be loud and proud about it: having to deny the humanity of embryos suggests you’re avoiding cognitive dissonance or trying to manipulate others.