This idea was originally from Lamarck, a scientist who was studying animal populations and cheking onto their patterns.
When you think of Lamarck, it's very easy to see where the problem with this hypothesis is, for example, when a father, that usually goes to the gym, walks every day, has lots of well developed muscles, has a son, is this son going to be strong just like his father when he's born? The answer is, of course not, he needs to go to the gym too right? But be careful, nowadays we have a new thing coming up that is called epigenenics, this is almost as Lamarck described, a fenotype being developed and going to other generations, but it's far more complicated than he had ever imagined it to be.
