N'ọgwụgwụ 1950s, Ivan Terence Sanderson, onye America na-ahụ maka ihe okike, kesara akụkọ na-atọ ụtọ banyere akwụkwọ ozi o nwetara n'aka Alan Makshir, onye injinia guzo na Shemya Island na Aleutians n'oge WWII.
Mgbe e nyere Alan Makshir na ndị ọrụ ya ọrụ ịrụ ebe mgbada, ha na-amachaghị emebi ugwu ole na ole ma chọpụta ọkpụkpụ mmadụ n'okpuru ụfọdụ ebe mgbada. Ha rutere n'ebe yiri ebe e liri ụfọdụ nnukwu ozu mmadụ, gụnyere nnukwu okpokoro isi na ọkpụkpụ.
Site na ntọala ruo n'elu, otu okpokoro isi dị sentimita iri na otu n'obosara yana sentimita iri abụọ na abụọ n'ogologo. Okpokoro isi ndị okenye na-ahụkarị bụ sentimita asatọ n'ogologo site na azụ ruo n'ihu. Nnukwu okpokoro isi dị otú a nwere ike ịbụ naanị ihe onwunwe nke nnukwu mmadụ.
Dị ka nkwupụta e nyere n'akwụkwọ ozi ahụ si kwuo, n'oge gara aga, ndị dike ahụ nwere ahịrị nke abụọ nke ezé na ndị na-enweghị isi. N'akụkụ elu nke okpokoro isi nke ọ bụla, e nwere oghere a kpụrụ akpụ, nke a kpụrụ akpụ mara mma.
Ndị Mayan nke Peru na ndị Flathead India nke Montana na-amanye okpokoro isi nwa ọhụrụ iji manye ya ka ọ tolite n'ụdị ogologo.
Mazị Sanderson chọkwuru ihe akaebe mgbe ọ natachara akwụkwọ ozi nke abụọ, mana o kwughachiri enyo ya. Nke Ụlọ ọrụ Smithsonian ejidela ọkpụkpụ ihe omimi ahụ, dị ka akwụkwọ ozi abụọ ahụ siri dị.
Maazị Sanderson maara na Smithsonian Institution nwere ọkpụkpụ ahụ, ọ gbagwojurukwa ya anya ihe mere ha ji jụ ime ka nchoputa ha pụta n'ihu ọha. "Ndị mmadụ enweghị ike ịmegharị akụkọ ihe mere eme?" O juru ya anya.
