Complex sentence: The dissimilarity of the remaining genes to any that are known led the researchers to speculate that this virus may represent a previous unknown branch of the tree of life; however experts not involved in the study have called that suggestion premature.
Split into simpler sentences: The dissimilarity of the remaining genes to any that are known led the researchers to speculate that this virus may represent a previous unknown branch of the tree of life. However, experts not involved in the study have called that suggestion premature.