Its origin (Nature’s or evolutionary adaptational method) can be traced to the amphibian period millions of years ago. It may be observed in the frog today as part of an adaptational feature of the free swimming propulsional cycle of webbed hind extremities. With skin contact or resistance against the plantar and dorsolateral surface of the lower paddle extremity, the distal webbed portion reflexly assumes a fanned out state in preparation for applying the largest possible area for the propulsion effort, so that the water, sand, mud, or solid matter may be used as a base for projecting the trunk-head in the desired direction. Similar sequence of adaptation is noted in the undulating fish fin fanning.
Subsequently, the landforms of vertebrates and mammals modified the original web structure and purpose of propulsion. Moving the hoof/foot backward, brushing the sole against the media(mud, sand, rock or fixed object), causing immediate spreading of the webbed portions of the extremity, to prepare a wide and secure background of the field, in anticipation of the next projectional effort.
In humans, curiously, placement of five-day infants on the abdomen in shallow water revealed similar patterns of movement with extension of the great toe and fanning of the remaining digits upon surface contact simulating portion of the primitive propulsional adaptative pattern displayed in amphibians. As the pyramidal tract becomes more mature, gradually the foot extensors stop being a part of the flexion synergy. In adulthood, the flexor plantar response becomes dominant and the great toe goes down upon plantar stimulation.