Section 1.1: The Species Dilemma

Commonly, we categorize living organisms—humans, ants, and bananas—as distinct entities. This classification seems straightforward, yet it is fraught with complications. The scientific concept of "species" presents numerous challenges, leading to debates among biologists. To arrive at a functional definition of "species," it's essential to consider the origins of life itself.

The prevailing understanding is that all current life forms evolved from a single ancestral cell that divided and diversified. Consequently, the boundaries separating species are largely arbitrary, lacking clear delineations. This ongoing debate is known as "the species problem."

Occasionally, biologists identify groups of organisms based on reproductive isolation. However, this criterion is more of a practical tool than a definitive measure. For distinct species to exist, transitivity must apply; if species A is the same as species B, and species B is the same as species C, then species A should also align with species C. Yet, instances arise where A can reproduce with B, and B with C, but not A with C—leading to logical inconsistencies.

Recognizing these complexities, biologists have attempted to broaden the definition to include geographical isolation as a factor. This approach, however, poses significant issues for humans. Approximately 15,000 years ago, a group of humans migrated to the Americas across an ice bridge, later severed by melting ice. This isolation lasted roughly 10,000 years, suggesting that these populations might be considered a different species from their Asian relatives. Nevertheless, most biologists would disagree with this classification.

Section 1.2: Potential Definitions

Currently, no universally accepted definition of "species" exists. Charles Darwin deemed it a futile endeavor, attributing the various competing definitions to the challenge of "defining the undefinable." However, I propose a definition that may hold merit.

If we assume all life on Earth descends from one organism, we must also consider the possibility of life originating independently elsewhere. This raises the intriguing idea that the entire biosphere could be viewed as a single species, while unrelated life forms from other origins would be classified as different species. Similarly, if life were synthesized in a laboratory, it would also qualify as a distinct species.

This perspective offers a biologically grounded conceptualization. Viewing a species as the cumulative biomass descended from a common ancestor allows for transitivity within the definition. Even when genetic material is exchanged through processes like conjugation, the lineages remain separate. A violation of this definition would require sexual reproduction between two different lineages, a scenario unlikely to occur with theoretical entities like Vulcans and humans.

Section 2.1: Rethinking Biodiversity

The term "species" often comes up in discussions about populations and biodiversity, particularly concerning extinction rates influenced by human activity. Given the ambiguous nature of species classification, this term may not serve as an accurate indicator of biodiversity loss.

In an era when DNA sequencing was not readily accessible, relying on the vague notion of species may have been our best option. Today, however, we can generate comprehensive genetic databases, enabling a clearer view of genetic diversity within the biosphere. Tracking genetic richness loss might provide a more insightful measure than merely counting lost species over time.