I read that book when it came out. Really liked it, but, from that link:
"The reasoning of 1421 is inexorably circular, its evidence spurious, its research derisory, its borrowings unacknowledged, its citations slipshod, and its assertions preposterous ... Examination of the book's central claims reveals they are uniformly without substance."
If I'm interpreting parent correctly, they're arguing that had the Chinese recently visited the Americas, the Portuguese and Spanish would have encountered native populations which were already decimated by disease. As this isn't the case, the epidemiological argument against shortly prior Chinese encounters with American populations is strong.
That post Portuguese/Spanish contact native American populations were annihilated by disease is now well established fact. That again argues against earlier Chinese contact.
>native American populations were annihilated by disease is now well established fact
Conveniently formulated historic fact absolving settlers IMO. Apropo to topic.
Convincing argument from indigenous is that indigenous in NA didn't get wiped out "because of" disease, worst historic pandemics wipe out like 50% of population over ~10 years before some sort of immunity kicks into population and gen pop rebuilds a few generations after that. Indigenous NA got wiped due to generations of increased deprivation enforced by settlers over 100+ years that made them suspectible to disease/fatality. It's like how malaria, dysentery, starvation was primary cause of death in prison camps, but really it's the fact that prison camp conditions allowed those diseases to spread in enviroment of artificially sustained deprivation.
90% population wipes over multipe generations isn't how disease operates, it's not natural epidemiologic behavior on continental scale. 90% population wipes happens because of coordinated genocide over generations across continent, blaming "contact" and "disease" is deflection. Hence if prevous visitors (can be whoever) didn't stick around for 100 years to coordinate a genocide, the indigenous people would still be around to greet Portugese/Spaniards, because they would have had ~100 years to recover/rebuild from whatever contact disease from prior meeting.
You seem to be arguing against your first comment to this thread.
Why take an account from an author of dubious qualifications and veracity seriously if the most significant evidence of such an encounter is entirely lacking?
"The reasoning of 1421 is inexorably circular, its evidence spurious, its research derisory, its borrowings unacknowledged, its citations slipshod, and its assertions preposterous ... Examination of the book's central claims reveals they are uniformly without substance."
Whelp!