Jungle beats, originally cut from the hip hop breakbeats of the 70s and 80s, developed from their early form as equipment would allow. Many loop samplers around the time of Jungle's emergence would not accommodate beats faster than 150 BPM, and as technology adapted, artists made beats specifically for jungle, often out of beats sampled from old records. Drum machines were also employed, as their design allowed.
One of the original jungle breaks, a classic that is still in common use and misuse today, is the amen break, from a funk song called "Amen Brother". The energy and intensity of this particular breakbeat is a perfect example of what drives jungle and drum and bass.
Jungle vs. drum n bass
Jungle is a blanket term that covers drum and bass, jump up, dancehall, 2-step, drill n bass, ambient dnb and many other subgenres, all with different sounds and esthetics. Pure Jungle often employs an MC's rasta vocals and rapping. drum and bass tends to be more dark, while jump up and dancehall are geared more to dance club environments.