According to Darwin’s theory of evolution, individuals in a species pass successful traits onto their offspring through a process called “deterministic inheritance.” Over multiple generations, advantageous developmental trends — such as the lengthening of the giraffe’s neck — occur. An opposing theory says evolution takes place through randomly inherited and not necessarily advantageous changes. Using the giraffe example, there would not be a common neck-lengthening trend; some would develop long necks, while others would develop short ones.