Abstract:

Aims: What do higher or lower organisms mean, or, is there any hierarchy among different organisms, is a big question, not only of life sciences, but also of practical philosophy. To answer this question, we must return to its starting point, Darwin’s On the Origin of Species.

Progress: In this article I show that Darwin in his masterpiece used a lot of expressions that imply some meaning of “biological hierarchy” (a ladder of life), referring to seven different aspects or indicators: (1) the degrees of morphological rigidity and functional differentiation, (2) the degree of directional development of traits, (3) morphological complexity, (4) competitive strength, (5) the time of phylogenetic differentiation, (6) evolutionary rate, and (7) taxonomic rank. Further analysis demonstrates that these different indicators, except indicator (7), can generally keep consistent with each other within Darwin’s theory of evolution, that is, they are various manifestations of the phylogenetic tree driven by the biological interaction of competition. In this framework, the logic of a biological ladder can be understood.

Conclusion: Further investigation, however, shows that this understanding faces two major challenges: (1) probabilistic uncertainty pertaining to any law of life sciences and (2) a revision of Darwin’s mesoscopic-static theory of evolution, which is dominated by biological interactions, taking into account the macroscopic-dynamic evolutionary schema, which is subject to changes in the external environment. In a considerably variable environment, evolution has no goal or direction, whether predetermined or predictable, factual or desirable. Therefore, with respect to macroscopic evolution, what could be called “biological ladder” tends to be an expedient metaphorical expression with little substantial meaning, let alone axiological implications. This conclusion also constitutes the criticism of Social Darwinism and naturalistic environmental ethics on the ontological level.

Key words: Darwin, evolution, competition, survival of the fittest, phylogeny, Social Darwinism, naturalistic environmental ethics