The reaction to study a specific race in the Biology lab uses any soul. I built one, thinking it might be useful later on. I decided to look at it, and saw that all the reactions were white. I ran one, and my dwarf grabbed a soul from a Mountain Tuskox soul. I canceled the reaction and made a stockpile of nothing set to give to the workshop (to see what the reactions took), and it said they took "SOUL plants", but the greater races give greater souls.
The reaction to study a specific race in the Biology lab uses any soul. I built one, thinking it might be useful later on. I decided to look at it, and saw that all the reactions were white. I ran one, and my dwarf grabbed a soul from a Mountain Tuskox soul. I canceled the reaction and made a stockpile of nothing set to give to the workshop (to see what the reactions took), and it said they took "SOUL plants", but the greater races give greater souls.