Who is credited with formulating the theory of relativity? Albert Einstein, of course. But Einstein got his uniform motion-state of rest idea and his speed of light idea from two less-heralded physicists - one a Scotsman and the other a Frenchman (see Chapter 11).Who introduced jazz to America in the 20th Century? Many say Duke Ellington or Louis Armstrong. But they simply inherited jazz from a pair of 19th Century-born musicians, one the son of a slave and the other the son of Creole parents (see Chapter 4). Who was the first Afro-American player inducted into the Baseball Hall of Fame? Answer: Jackie Robinson. But, older than Robinson, and paving his way into the Big Leagues, were two superstar, black baseball players in the old Negro Leagues, the legendary Satchel Paige and the slugging, so-called Black Babe Ruth (see Chapter 2).Who was the world’s first evolutionist? A clue: it was not Charles Darwin. Preceding Darwin with their own versions of natural selection were a competitor of Darwinand Darwin’s own grandfather (see Chapter 5).Is Bernie Sanders the world’s oldest socialist? Of course not. That honor goes to an ancient Greek philosopher and to an Englishman beheaded by King Henry VIII (see Chapter 13).Who was America’s most famous practitioner of civil disobedience? Most would say Martin Luther King, Jr. But King adopted his non-violence from two earlierpassively resisting protesters, both of whom are more commonly associated with their literary accomplishments - one a New Englander and the other a Russian (see Chapter 12).Were the Suffragettes and Womens’-libbers of the 20th Century the first feminist activists? Hardly! That role was played by an 18th Century wife of a poet and a 19th Century husband of the writer of Enfranchisement of Women (see Chapter 3).The title, KINDRED SPIRITS, plural, denotes the two avant-garde comrades in arms in each chapter, the pair, ahead of their time – the unsung pioneers of modernity.