Subject: Is there any solid evidence about Intelligence being hereditarily linked?

i am really puzzled and have been in debate with a friend of mine (whose 
parents are doctors)about inteligence being hereditarily linked, he argues 
that some people are born smart while others are just born DUMB.i on the 
other hand believe that people are molded because of the exposure and the 
environment that they grow up in. i just really want to know if there is 
solid evidence reagarding this matter. 

Re: Is there any solid evidence about Intelligence being hereditarily linked?