Results of the study are published in the Jissue of the journal Mammalian Genome. Scientists use this method because mitochondrial DNA is more accessible, easier to sequence, and all multi-cellular animals have mitochondria, whereas all animals do not share the same nuclear genes.

Mitochondria are the cell's power plants and possess their own genes that are inherited through the maternal line. Their own research using nuclear genes (genes from the nucleus or core of cells) has shown a nearly 100 percent statistical likelihood that the Duke results are correct. Using a more comprehensive method to analyze the genetic material of 15 types of mammals, Duke researchers have shown that the mitochondrial DNA method that links disparate animals (hippo and whale, kangaroo and platypus) is statistically unreliable when it comes to evolutionary genetics, said Randy Jirtle, professor of radiation oncology at Duke University Medical Center. The mitochondrial DNA method of analyzing mammals has turned on its head the common-sense approach of linking mammals by similar anatomical traits or 'morphology,' they said. Classifying kangaroos and platypuses together on the evolutionary family tree is as absurd as adding your neighbors to your own family ancestral line simply because they share your love of the opera, according to scientists at Duke University and Duke University Medical Center.īut the current molecular method of using mitochondrial DNA to classify how mammals evolved is so flawed that it might have erroneously linked very different mammals, the scientists said.

Platypus evolution tree