Of Natural History is the second album by avant-rock group Sleepytime Gorilla Museum. It was recorded and mixed at Polymorph Recording in Oakland, California during the years 2003 and 2004. Whereas on the first album, Grand Opening and Closing, Dan Rathbun handled the mastering (in addition to producing, recording, and mixing), on Of Natural History the mastering duties are handled by Justin Weis, who mastered the album at Trakworx, San Francisco.
All the tracks on this album were produced by Rathbun & the other members of the band, except for "Phthisis", which was produced by Scott Humphrey, and recorded at the Chop Shop, Hollywood in May 2004; Chris Baseford engineered the recording sessions, while Garry Raposo and Vincent Piette assisted in engineering.
Interestingly, like with the first album, this album again marks the transition from one drummer to another: Frank Grau, who replaced David Shamrock after the first album, left after this album, and Matthias Bossi took the drummer's position and has held it since then (Bossi plays different instruments on the tracks "Phthisis", "FC: The Freedom Club" and "Gunday's Child").
Of Natural History continues on the same diverse and eclectic musical lines as its predecessor, with even more new elements, like dance music ("Bring Back the Apocalypse") and funk and jazz ("Gunday's Child"). Also notable is the incorporation of a plethora of field recordings and samples into the songs and interludes.
Of Natural History has a continuity in the sense that all the songs sequence into each other, thus holding the narrative element(s) of the album better together along the album. The continuity and the coherent feel make Of Natural History very close to a concept album. While the lyrics themselves differ much from song to song, the underlying imposing mood is concerned with the apocalyptic implications caused by human presence on earth; to offer different viewpoints on this, SGM create their own characters and stories (tracks 1 & 2, both of which are a continuation of a story created already on the first album that was non-musical) and borrow from Filippo Tommaso Marinetti, Unabomber, Muriel Rukeyser and Kenneth Patchen (tracks 3, 5, 6, and 9, respectively) in addition to own lyrics.