The Pharaonic dynasties of the Egyptian civilization alone goes back to 3200 BCE, supported by actual historical records. Evidence of Egyptian pre-history dates to around 6000 BCE.
Evidence of ancient Sumerians goes back to 6500 BCE with written records also at 3200 BCE.
Mesoamerica has evidence of maize cultivation by 5100 BCE.
There are/were trees in California over 5000 years old.
They simply ignore facts to support their timeline.