Given the rationale, provide a reasonable question and answer. Step-by-step reasoning process: To answer this question, we should know that: Finding Your Roots with Henry Louis Gates Jr. is a documentary television series hosted by Dr. Henry Louis Gates Jr. that airs on PBS.
The question and answer:
Finding Your Roots with Henry Louis Gates Jr. is a documentary television series hosted by Dr. Henry Louis Gates Jr. that airs on PBS. In each episode, celebrities are presented with a "book of life" that is compiled with information researched by professional genealogists that allows them to view their ancestral histories, learn about familial connections, and discover secrets about their lineage. The series premiered on March 25, 2012. Season four concluded airing on December 19, 2017.

Who is the host of finding your roots?
The answer is Dr. Henry Louis Gates Jr.