Keep writing Brian. Someone should be able to come up with some viable answers. It might as well be you.
When it comes to the discussion at hand, I approach the subject from the viewpoint of the operation of complex systems. Nature is a complex system; and, subsets of this uber system are plants, animals, electromagnetic radiations, earth's weather patterns and atmosphere, geological shifts in earth's foundational materials, and even materials and animate and inanimate objects modified and created by intelligent beings, since these are, by definition, only expedient and transitory rearrangements of natural complex systems re-fashioned to suit our needs. Everything within this categorization is entirely composed of a fixed number of naturally occuring elements, arranged with each other in varying combinations. As far as we are able to see in the observable universe this all seems to be the case.
So think of all our earthly realities as nested sets of macro and micro complex systems that tend to come into being naturally or artificially, that exist for differing time spans in certain forms, and then tend to transform themselves because of environmental necessities into other sorts of complex systems. Such transformed systems are not necessarily very different from what came before, but just different enough in order to, perhaps, adapt more effeciently to the new and changed environmental order.
Water is a complex system, yet it may exist in at least three forms on the earth or in the atmosphere; steam, liquid, or as a solid. The phase changes that mark the shifts between the forms exhibit hallmark patterns at the molecular and atomic levels as the changes progress. But these hallmark patterns are dormant once the stability of a new phase is attained.
This same or similar process takes place in living organisms as they change to adapt over time to environmental variabilities. If a Finch species in the Galapagos Islands adapts its beak characteristics to adapt to new food source conditions, it may or may not signal a permanent change in the animal and the establishment of a new species. It's a question of how long the new stability lasts. It depends upon one's definition of permanence. Beaks may change within another ten years or so because of other needed adaptations to feeding conditions. Can that also be considered a species change ? I believe that this is all a matter of degree and time spans.
Science is a series of measurements and observations that describe conditions in our environments of complex systems. It and its findings are always subject to adjustment and change depending upon the relative stabilities over time of what is being observed and measured. Looking at past objects gives us a series of pictures of past realities frozen in time, and by stringing enough of them together science has the ability to determine and, now, digitally model, over time, whether phenomena such as global warming trends are real, and what the causes might be. But these methods, such as stringing together humanoid fossils to determine our heritage, are notoriously incomplete because of the lengthy time periods involved. Actually, digital archaeogenetic analyses are currently yielding more fascinating versions and pictures of what we are and where we came from.
In living complex systems these things are much more difficult to theorize upon and to reach concrete conclusions about. These systems are much more sensitive to many more variables than, say, water is. They must also react and mesh with atmospherics, light, electro/geomagnetic variances, nutrient availabilities, etc., so there are many more things to observe and measure to determine accuracy and applicabiliy of any explanatory theories which may be derived in the process.
So saying that there have always have been three distinct varieties of humans and that they correspond with the stories concerning Noah's three sons may be true, but it could also just be a convenient metaphor to explain our possible genotype, phenotype, and cultural histories. In a like manner we might regard random genetic mutations within the human system to be transitory and not necessarily indicative of species change. It is clear that autism, attention deficit disorder, juvenile diabetes, increased allergen sensitivities and the like signal changes in the human system. But are they changes that signal some immense movement towards a permanent shift in the makeup of our species ? Maybe, maybe not. Time will tell.
But these days some epidemiologists are concerned that our species' shift away from living in natural as opposed to constructed environments over the past 150 years or so may be enough of an environmental imposition upon our system's stabilities to force cascades of genetic changes that may profoundly change all of us in significant ways.
flow....
