Again I ask a question, “What would a 900 year old + skull look like?”
The patriarchs of Genesis would not have been the only ones who grew old back then.
They all probably did.
My best guess is that the early earth conditions were optimal to live forever. Giant creatures ( which we can prove) and giant men (which the legends attest to) lived.
God cursed the Creation and man.
It then, took a slow turn to death.
We die, the creation dies. Birth pains.
Initially, they lived to a 1000 years because they were close to the beginning. But as time marched on, death approaches us all sooner and sooner.
We again have secular confirmation of Biblical events. The Global Flood is another.