 They also argue that YAP+ migrated back to Africa with other Eurasian haplogroups, such as Haplogroup R1b1* (18-23kya), which has been observed with especially high frequency among the members of some peoples in northern Cameroon, and Haplogroup T (39-45 kya), which has been observed in low frequencies in Africa.Haplogroup E at 50kya is considerably older than these haplogroups and has been observed at frequencies of 80-92% in Africa.In a 2007 study, Peter Underhill and Toomas Kivisild stated that there will always be uncertainty regarding the precise origins of DNA sequence variants such as YAP because of a lack of knowledge concerning prehistoric demographics and population movements.