I just finished reading the book "Your Inner Fish: A Journey into the 3.5-Billion-Year History of the Human Body."  I really liked this book for it's insights into how humans evolved.   The book provides examples of how we carry the history of evolution within our own bodies. 

 One example is the phenomenon of  hiccups. Hiccups are triggered by electric signals generated in the brain stem. Amphibian brain stems emit similar signals, which control the regular motion of their gills. Our brain stems, inherited from amphibian ancestors, still spurt out odd signals producing hiccups that are essentially the same phenomenon as gill breathing.