What major hominin group, for which we have an extensive fossil record, lived from approximately 4 to 1 m. y.a.

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what do the different brain waves do?

explanation:

brainwaves are produced by synchronised electrical pulses from masses of neurons communicating with each other. brainwaves are detected using sensors placed on the scalp. brainwave speed is measured in hertz (cycles per second) and they are divided into bands delineating slow, moderate, and fast waves.

answer///unconditioned stimulus;