Simplify the following text for a Grade 8 native English-speaking person.
Original: This can stem either from natural causes such as in Olaf Stapledon 's novel Odd John , and Theodore Sturgeon 's More Than Human , or be the result of intentional augmentation such as in A. E. van Vogt 's novel Slan .
Simplified: Two examples of this type are Olaf Stapledon 's novel Odd John and Theodore Sturgeon 's More Than Human .