Waxaa jira kaliya laba daahfurka diiwaan gashan ee burburka qoolleyda bog. Marxuum J. Alan Holman, oo ah khabiir cilmiga duugta ah iyo khabiir ku takhasusay duugta, ayaa markii ugu horreysay aqoonsaday qashin-qubka qoolleyda bog ee Cumberland Cave, Maryland (u dhow Corriganville), kuwaas oo ah da'da Irvingtonian (laga bilaabo 1.8 milyan illaa 300,000 sano ka hor). Daahfurka labaad wuxuu ahaa Rancholabrean (inta u dhaxaysa 300,000 iyo 11,000 sano ka hor) qaybo ka mid ah qolofka ku yaal Giant Cement Quarry ee South Carolina (u dhow Harleyville), oo ay sameeyeen Bentely iyo Knight 1998.
khabiir ku takhasusay dhirta iyo xayawaanada