THE LAW OF USE AND DISUSE:JEAN-BAPTISTE LAMARCK

Lamarck was one of the first scientists to understand that changes occur with time, and that changes are an adaptation to the environment. According to Lamarck, these changes are acquired during the organism's lifetime, and are then passed on to the offspring.
In his work 'Zoological philosophy' he explained a new theory he named as 'The law of use and diuse' which stated that organisms react to changes in their environment by changing or strengthening a determined organ. However, in the same way an organ can stop working or disappear if it stops being used. The changes that an organism undergoes have a tendency to go towards perfection, in order to acquire features to help them live successfully in their environment. Nevertheless, Lamarck's theory could not explain how were traits inherited from one generation to the other, and didn't convince the scientific society, as the theory didn't follow the scientific method (he could not prove it through experimentation).

Charles Darwin: Theory of Natural Selection

In 1859, Charles Darwin book "The Origin of Species" started a scientific revolution that still continues today. In this book, Darwin shows a visiopn of life that can be divided into 3 different points:

• Variation: Inside a certain species, there is always some variation, that is, no two living organisms are totally the same.
• Natural Selection: It is the mechanism that picks the characteristics that give an adaptive advantage to the individuals that have them, allowing their reproduction and their transmission to the next generation.
• Gradualism:With the pass of time, the individuals with the characteristics will become the majority of the species, making the species evolve and change gradually over time.

The impact of Darwin's theory on the rest of the world was enormous, and because of it there are various important consequences:

• Similar organisms are related (if we go back in time, we will get to the point where all living organisms come from the same place, called the LUCA, or the Last Universal Common Ancestor).
• Variation is totally random, and natural selection is a filter over characteristics that are adaptative to one certain place. this means that one characteristic can be better for one place and worse for a different place.
• It puts mankind in nature as another of many species. this was the most polemic consequence.