If there is a heavy growth of hair on the body... then it is said to b atavism since these represent ancestral characters which are no more present in human of this generation....

Atavism refers to the reappearance of ancestral characteristics in an organism that are not currently present in its immediate ancestors. It is a phenomenon that occurs due to the activation of dormant or suppressed genes that were once present in the organism's evolutionary history.

Ancestral characters reappear

Atavism is characterized by the reappearance of traits or features that were present in a distant ancestor but have been lost in the intermediate generations. These ancestral characters can manifest in various ways, such as physical features, behaviors, or even genetic traits. For example, a human may exhibit a tail-like appendage, similar to that of our primate ancestors, or a horse may possess an extra toe, resembling the three-toed structure of its evolutionary predecessors.

Activation of dormant genes

The reemergence of ancestral characteristics in atavism occurs when dormant or suppressed genes are activated. These genes may have been silenced or rendered non-functional over the course of evolution, but under certain circumstances, they can be reactivated, leading to the expression of ancestral traits. The reactivation of these genes can be triggered by genetic mutations, environmental factors, or other unknown mechanisms.

Evidence of evolutionary history

Atavism provides valuable insights into an organism's evolutionary history by offering glimpses into the traits and characteristics of its ancestors. It serves as evidence of the shared ancestry between different species and highlights the genetic connections that exist across evolutionary lineages. By studying atavistic traits, scientists can gain a better understanding of the evolutionary processes that have shaped life on Earth.

Conclusion

In summary, atavism refers to the reappearance of ancestral characters or traits in an organism. It occurs when dormant or suppressed genes are activated, leading to the expression of traits that were present in distant ancestors. Atavism provides evidence of an organism's evolutionary history and helps scientists unravel the complexities of evolution.