Some anthropologists say early humans were scavengers, not hunters

[Korn]

Hunting ancient scavengers - some anthropologists say early humans were scavengers, not hunters
(http://findarticles.com/p/articles/mi_m1200/is_v127/ai_3677563)



But reexamination of the bones and tools, some nearly 2 million years old, with electron scanning microscopes has convinced some scientists that early humans were scavengers, not hunters. The location of minute cut marks on many bones suggests that parts of scavenged carcasses were taken back to the ancient sites, where tools were stored (SN: 12/18/82, p. 390).

More here.
(http://findarticles.com/p/articles/mi_m1200/is_v127/ai_3677563)

[burl]

Most certainly, Humans didn't go from eating tubers and berries to hunting outright. Just like every other process humans built up to hunting on ce they realized that it was possible.