“At that point it’s indistinguishable from an embryo of a dolphin”

So we don’t know if embryos in humans are actually human?

The argument you are actually making is that it is visually indistinguishable from other embryos .

But this is meaningless, visual inspection is not the only allowed method for determining categorization. One wouldn’t look at a human in a realistic bear costume, and a bear and declare that they are the same thing. Or a stick-bug and a stick.

“It can’t even think yet”

There are numerous intervals of time were you don’t think, are you not worthy of protection? Can you be killed so long as neural synapses are severed faster than axons can fire? (Highly intense radiation can do this). Keep in mind that your argument completely falls apart once you consider that consciousness is a pattern of activity not a definite property.