The idea of acquired characteristics proposes that certain characteristics acquired during the life of a parent organism can be passed to its offspring. In this theory also known as Lamarckism, individual efforts acquired during the life of a parent organism were the main mechanisms that drive species to adaptation. This is majorly because they would acquire adaptive changes and pass them to their offspring. This theory was proposed by Jean- Baptiste Lamarck. In this theory, Lamarck incorporated two main ideas which at that time were considered to be true. The first idea he based his proposition on was that of Use and disuse. In this he stated that individuals lose characteristics that they do not find useful to them and develop those that are useful to them. The second main idea behind Lamarckism is that of Inheritance of acquired traits. This idea basically relates to the traits individual organisms inherit from their ancestors.
In essence, according to Lamarckism, a change in the environment brings about change in "needs", resulting in change in behavior, bringing change in organ usage and development, bringing change in form over time - and thus the gradual transmutation of the species. Natural selection on the other hand is a process by which traits are modified by the consistent effects upon the survival or reproduction of their bearers. This is what generally described evolution in context. Darwin, who is a great proponent of this theory states that natural genetic variation within a certain population of organisms may cause some individuals to survive and reproduce more successfully than others in their current environment.
Root-Bernstein employs the questioned Lamarckian theory of evolution by transmission of inherited somatic modifications to support evolutionary theory and still not challenge out of his student religious beliefs. Having proved to his students that that theory to be wrong, he then explains to his students that for the same rationale one offspring would still have thumbs even if their parents would have had theirs chopped of, Adam's offspring would have the typical number of ribs although God removed one of his. If it did happen, then it would be Lamarckian inheritance which is by now established incorrect. He then explains to the class that even if Lamarckian evolution hypothesis was to be valid, all Adams descendants, both males and females, would take over his number of one ribs since ribs are without doubt not a sex linked trait similar to too much facial hair.
He also explained to his students that there is not a thing that is written in the bible to suggest how many ribs Adam had before one was taken so we cannot look forward to to knowing if one absent by counting. In the end he manages to illustrate to his students that the real number of ribs in men and women does not in any way insinuate that the creation theory is not true and also one that one cannot use a questionable hypothesis to question religious beliefs. He also manages to show the students that the number of ribs in men and women supports both the creation theory and the evolutionally theory.
There is thus a disparity between Lamarckism and Darwinian school of thought. In Lamarckism the evolution of species is entirely based on the individuals themselves while in Darwinism it is because of survival that species evolve. The idea of survival for the fittest best brings itself out in the Darwinian school of thought. Lamarckian hypothesis hold that selection is a process that is non- arbitrary and environmentally determined while on the other hand Darwinian Theory posits that evolution develops by the process of differentiation and is a genetically random. Darwinian school of thought holds that organisms evolve to attain a characteristic that they need through inner requirements or by use and disuse. Another difference is that in Darwinism, mutations are not meant to necessarily profit the creature; rather, it is a random process of selection.