How much of my body from 40 years ago is part of me today? (part 2)

I am 65. Assuming that I still weigh what I did at 25 (I wish!), what percentage of material from 40 years ago remains as part of me today? (continued)

Tobias Bast
School of Psychology, University of Nottingham, UK

I wanted to pick up on a previous response to this question, which suggested that neurons in our brains are continuously replaced and an 80-year-old would retain virtually no neurons from their 20-year-old brain.

The formation of new neurons in adult brains, known as adult neurogenesis, is well established in many animal species, although evidence for it in humans is somewhat…