The species problem

THE THREE SPECIES PROBLEMS

The species problem is actually a number of problems that biologists have dealt with since the term was first applied to biological organisms by Aristotle. I call the three main problems the grouping problem, the ranking problem, and the commensurability problem. It will benefit us to clearly distinguish these at the beginning of our discussion and to bear them in mind as we consider the philosophy of species.

What is a species?

From Appendix B in Species: A History of the Idea (2nd ed.) by John Wilkins:

Microevolution and macroevolution

What's the distinction between microevolution and macroevolution?

Traditionally the distinction is supposed to be at the species level. Micrevolution involves evolutionary changes within a species, while macroevolution involves evolutionary changes beyond a species. Such as when one species becomes another species. Or one species becomes two species (speciation).

1. Yet, today, many scientists disagree with how to define a species. What, precisely, makes a species a species?

2. Also, why is the focal point of macroevolution at the species level? Why is species where we draw the line between microevolution and macroevolution? After all, isn't evolution supposed to be akin to climbing Mt. Improbable? If so, then evolution is simply a gradual but continuous series of changes in one direction (give or take). Hence, why couldn't the line be drawn elsewhere?

3. In fact, is it even a line so much as an outline or sketch? A fuzzy boundary?

4. Moreover, aren't there multiple blurred lines?

5. As such, the traditional demarcations between microevolution and macroevolution seem to overemphasize the significance and roles of species and speciation.

6. Yet, if the borders are hazy enough between microevolution and macroevolution, then that could potentially affect the theory of evolution as a whole. After all, of what use are concepts like microevolution and macroevolution if the borders are so hazy? We might as well simply call microevolution "small change" and macroevolution "big change" for all the explanatory power these terms have.

7. Macroevolution is supposed to be reducible to microevolution. Macroevolution is supposed to be the accumulation of small genetic changes over time (microevolution). Macroevolution is a continuous spectrum of microevolutionary changes.

   All this requires genetic changes. How do genetic changes occur? There are several ways, but the primary driver of these small genetic changes is supposed to be random mutations. In addition, these genetic changes can't be deleterious mutations, or even neutral mutations, but they must be beneficial mutations, in order to drive phenomena like speciation. However, the vast majority of mutations are not beneficial mutations. And according to mathematicians, the problem isn't solved even if given hundreds of millions of years to work with.