According to Merriam-Webster (2013) the definition of atavism is "recurrence in an organism of a trait or character typical of an ancestral form and usually due to genetic recombination" or "recurrence of or reversion to the past style, manner, outlook, approach, or activity".
Merriam-Webster. (2013). Atavism. Retrieved from http://www.merriam-webster.com/dictionary/atavism
In an article by Tomic & Meyer-Rochow discuss the idea of atavism through medical, genetic, and evolutionary perspecitives. One of the major challenges with this concept is that scientists struggle to tell the difference between atavism and a mutation. Originially the term atavism was used in a negative way, but over time it has changed into the definition that we know today. In order for a trait to be classified as atavism they must have the following criteria:
1. a high level of physical resemblance to a distant relative.
2. appearing as a fully developed adult
3. noted as a rare occurance throught the population; only occuring a few times
4. an organism cannot display something that was not found somewhere in their lineage
Tomic, N. & Meyer-Rochow, V. (2011). ATAVISMS medical, genetic, and evolutionary implications. Perspectives in Biology & Medicine, 54(3), 332-353.
Examples of atavism include an extra nipple or tail in humans. The article states how scientists located a dolphin with an extra set of flippers. It is strange to think that a "lost" characteristic could suddenly reappear in the genetics of an organism.
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