The human body is the same as it was before your doctor was born.

Medicine however is not the same. Nor is our understanding of the human body.

For example, a 60 yo doctor would have been born before the first heart transplant, the recipient lasted 18 days. Now 5000 are performed each year and after 5 years 80% of recipients are alive.

The Earth was mostly the same in the 1300's. Let's use material from that time to do engineering.