Question

1. Explain the difference between ideas of Lamarkian and Darwinian evolution using giraffes as an example. Explain how what we know now made them both partially correct. What was Darwin missing to complete his ideas? What did Lamark get wrong?

Answer 1

Lamarckism was based on the idea that according to the environmental changes that take place, Organisms acquire new characteristics by developing new organs based on their increased use or disuse of the said organ and this acquired trait was passed onto the next generation. For instance, According to Lamarckism, Giraffes did not originally have long necks as they have now. To keep themselves fed, they reached for the higher up leaves and this resulted in them stretching their necks and caused the elongation of their necks. This trait was passed onto the succeeding generations. Lamarckism implied that each generation of giraffes had longer necks than the previous generations. But, this theory failed to explain the existence of simple unicellular organisms. It was assumed that organisms developed more and more complexities as the environment continued changing. It is a well-known fact that there are several species of unicellular and simple multicellular organisms existing on this planet without developing any new organs. This theory also blurred the lines between acquired and inherited traits. As we know now, acquired traits which occur due to the interaction of the organism with its environment are not passed onto its progeny.

Darwinism, on the other hand, states that beneficial traits already present in organisms allowed them to survive rather than developing new traits. This theory put forth the idea of natural selection, which explained that organisms were born with variations which made them more likely to survive and reproduce in their environment and these variations were passed on to the next generations. In the context of the previously stated example, Longer necked giraffes were more likely to survive, hence the next generations constituted of long-necked giraffes. However, This theory failed to explain the origin of variations.