Kanzi says, "nobody makes a monkey out of me!"
The problem with defining personhood is that depending on how broadly you define the term, you start including a lot more members into the club of "personhood" that aren't necessarily human, and start to exclude a lot of humans.
A corporation is legally a "person", but it isn't human. Is dissolution of a corporation on par with homicide?
And how about dolphins and chimpanzees? Undoubtedly some of them are more intelligent and literate than a lot of humans.
Should they be considered persons, with equivalent rights as human persons? If not, why not? Should personhood be dependent entirely on chromosome count? Before you answer yes, understand that you risk excluding people with Down's Syndrome. We'll get back to that.
Pictured above is Kanzi, a male bonobo with a command of pictogram vocabulary of about 450 words. He can communicate intelligently with scientists and reporters, which is more than one can say for many politicians. He can also craft stone knives using ancient flint-knapping techniques, build a fire and toast food on it, without the use of lighter fluid, match-light briquettes or compressed propane gas. These are skills that I have observed to be lacking in many supposedly intelligent humans.
I would say that Kanzi is a person, and that all chimps, bonobos and other great apes are at least as much potential persons as the least intelligent members of our species. A normal human has forty-six chromosomes. A chimpanzee has forty-eight. A person with Down's syndrome splits the difference, with forty-seven. Notably, 98 percent of our 21st chromosome is identical to that of a chimp. The 21st chromosome is the one that is duplicated in Down's Syndrome humans. Genetically and behaviorally, a Down's Syndrome person has at least as much in common with a chimp as with a human. Maybe more.
I mean no offense to Down's Syndrome people. This is just the way it is. Severely disabled Down's Syndrome people could not compete with Kanzi in terms of manual dexterity, reasoning or communication.
Either a chimp is a person, or a Down's Syndrome person is not. My money is on the former.