Ska actually came before reggae. Yes, that's right. Most American fans think that reggae came first because they've been hearing about reggae since the late 1960s and early '70s but have only heard of ska since the 1980s and '90s.
Jamaican bands in the 1950s loved covering the famous R&B hits they heard on the U.S. radio, but they had some fun with it when they added some quick-paced jazz beats and a strong horn section. Ska soon transitioned into rock steady, which mixed Jamaican sounds with American soul hits coming from artists such as James Brown. The transition continued through rock steady to reggae, which chose rock as the next influence to alter Jamaican rhythms.
Reggae actually made its way to the U.S .in the late 1960s and became mainstream thanks to reggae tributes by big artists such as Eric Clapton, who popularized "I Shot the Sheriff."
Although ska started the post-World War II music revolution in Jamaica in the 1950s, which music historians refer to as the "first wave" of ska, it soon left Jamaica to become all the rage with British mods during the 1960s and '70s. This "second wave" in England was followed by a "third wave" in America, which hit in the 1980s and became immensely popular in the '90s.
Ska is distinguished by a "walking bass line" colored with rhythms at the upbeat. Reggae emphasizes the "off-beat" and does this at a slower pace than ska. This is exemplified by how each genres utilizes horn sections. Ska horns have a fast punchy beat, while reggae horns are soft and soothing.