A 2011 ancient DNA study of the complete mitochondrial genome (inherited through the female line) showed that two examined Columbian mammoths, including the morphologically typical "Huntington mammoth", were grouped within a subclade of woolly mammoths. This suggests that the two populations interbred and produced fertile offspring. One possible explanation is introgression of a haplogroup from woolly to Columbian mammoths, or vice versa. A similar situation has been documented in modern species of African elephant ("Loxodonta"), the African bush elephant ("L. africana") and the African forest elephant ("L. cyclotis"). The authors of the study also suggest that the North American type formerly referred to as "M. jeffersonii" may have been a hybrid between the two species, as it is apparently morphologically intermediate. These findings were not expected by scientists; nuclear DNA and more specimens will have to be examined to clarify the situation.