Switch is an action performed by pressing the appropriate button when available.
This action is not the same as the Switch Hands action which is used to change what hands are holding.
This action will only appear if you are close enough to another member of your clan and oriented to face them. Press the appropriate button and a very short animation cut-scene will take place showing black and green neurons moving through space showing you transferring consciousness to the other hominid. You orientation/view will change and you will then be on control of the other hominid. To change back, face the other hominid and press the appropriate button again.
As long as the hominid is a member of your clan you can switch to that hominid.