Sci-fi book identification-Feral Child to Superhuman

I read a sci-fi/thriller novel many years ago, probably published between 1980-1990 in the USA in English that had the following elements:

1. A feral child/teen is found in the wilderness, but his brain is underdeveloped.


2. Scientists "fix" him with a brain tissue transplant to increase his intelligence.


3. The child rapidly develops vast intelligence, surpassing his doctors.


4. The doctors hire a prostitute to do an experiment on the teen/experiment


5. Teen develops telepathy


6. Teen uses super brain to augment another low-intelligence female patient.


7. The book ends with the end of the world and the teen and his newly-enhanced female friend watch the end of the world from a jungle. There is a definite Adam/Eve vibe to the ending.


8. Protagonist may be named Adam.