Reductivism has greatly benefited science in that the ability to break down an area of study into a more neatly defined territory with relatively clear boundaries allows a researcher to get on with the work at hand and to have a higher hit rate of identifying that which is measurable in that set range.
However such an approach can suffer from a lack of holism and the danger of believing that the world does conveniently fit into the categories we place upon it.
A fascinating demonstration of this, as featured recently in an article in National Geographic, is the question over whether it is ethical to bring back extinct species through cloning methods.
Whatever the most appropriate answer may be, the question is raised as to what really constitutes an animal and what the criteria would be for successfully restoring one.
A reductive approach to take would be to, on a purely genetic level, clone an animal that has died out in the past. However without parents of its own species to raise it, possibly without the same environment and climatic conditions as its ancestors, and with potentially different dietary constraints, what would be the nature of this animal?
Rather like the observation of Heraclitus of never being able to step in the same river twice, it would seem that the natural variation from generation to generation means that no two animals are ever the same, though they may of course share certain common characteristics based on the tolerances we place upon the categories we call species.
However whilst the inevitability of change could be used as a license to bring back the dead, albeit in a new 21st century edition, it must be remembered that the burden of adaptation is something that is typically shared by all of the members of a species, interactively with their environment, over the course of time. Placing this amount of pressure to 'fit back in' on a single representative of a species may prove rather intense.
It strikes me that a good way forward in answering these types of questions is to not just map genomes, but also social and environmental factors, to at least attempt to have a more holistic picture of what makes a species. It might not yield an a clear answer, but definitely better data to base such a question upon.
Just as we would likely see it as inappropriate to clone an animal with only half a nervous system or with other imperfect and limiting conditions, it may be that the same concern needs to be placed on the context of that species in their environment.
Perhaps if it can be determined that a suitable environment and food source for a given species still exists, then this will count in favour of it being a candidate for de-extinction. The issue of socialising is a trickier one but some species, for example tortoises that hatch from eggs, tend to live more solitary lives so may be a more appropriate choice.
Another possibility is that herd animals may also be mixed with other herds, for example mammoths with elephants, however the results here may be questionable.
If all of the above conditions can be met then we have to question why the species is extinct to begin with. Granted it could have been circumstantial, or as a result of human hunting which could now be defended against, however it would take a very clear knowledge of all of the extended factors of what makes a species thrive in order to be able to address this question with any confidence. And reductivism, for all its triumphs, just doesn't seem like the right approach.
The full National Geographic article can be read here.