Warning this list may not be 100% accurate but cut me some slack I worked hard on this.
Using RYM I put every available genre here on AOTY and saw what was considered the first entry in that genre. Here is a very rough timeline of the history of recorded music and genre.
Genres that are just groupings of other genres or aren't on RYM:
Black Ambient
Dance
Hip Hop
Metal
Pop
Psychedelic
Punk
Raw Black Metal
Rock
Slacker Rock
Stenchcore
Amount of genres originating by decade:
Pre-1950: 54
1950s: 38
1960s: 75
1970s: 69
1980s: 129
1990s: 83
2000s: 25
2010s: 24