Use Simple Past tense for description?

Hi all,

I'm reading a transcript of a recording from Cambridge book on Vocabulary. In this transcript, there is one passage where the use of verb tense (highlighted in red) is not relevant for me:

"Now, the skulls of the Cro-Magnon people who inhabited the Earth 25,000 years ago show evidence of tooth decay and the earliest recorded mention of all disease was in 5000 BC. This proves that all disease is by no means a modern-day problem and has in fact played humans since time began. That particular reference appeared in a text written by the ancient people of Sumeria, which referred to “tooth worms”.

Since the reference always appears in this text and always refers to "tooth worms", should we just use the simple present tense?

In other passage of the same transcript, the author uses the simple present for introducing a historical thing:

"There is even further evidence of the troubles caused by toothache in the Ebers Papyrus, which is a text written between 1700 and 1500 BC by the people of the ancient Egypt. This papyrus contains references to diseases of teeth as well as the prescriptions for medications they used at that time."

Could you please help me to explain why the author use the Past tense in the first passage?

Thank you very much.