I’ve been thinking about the symbiosis between organisms and I want to present a different view that should simplify our understanding of the tree of life. With the rise of the computation of phylogenetic trees then this isn’t a new idea but I’m presenting it from a layman’s point of view.
Organisms use different processes of reproduction as a means of genetic survival but to consider a group of organisms that use a specific mechanism in isolation to the many other organisms that together ensure the survival of that genetic information is to me an arbitrary division of the genotype.
You can’t say that humans are a ‘separate’ species without considering the many thousands of different microbes that keep us alive. What keeps us alive is also what keeps us genetically fit.
We do this grouping into species though for convenience sake. We group organisms by reproduction and by features of the phenotype (the body). But that is just that. It is a rule of thumb or a heuristic that is arbitrary. It has been useful given for most of human history until modern times we have been ignorant of the genome.
The probability is that we have descended from a single replicator. This is supported by the science when we examine the genome of quite diversely expressed organisms. So there are not so many species but so many individual replicators which differ from all other replicators by a variable percentage of changes in the genetic material from that first replicator.
From a human point of view that’s pretty amazing as it means that there is information in your body, in your genome, that is over 3.5 billion years old from what is called the last universal common ancestor (LUCA).
That we group sets of these replicators by an arbitrary expression of the phenotype does not falsify the process of evolution of the genotype because we cannot explain the underlying gene sequences needed to explain the expression of the phenotype that we grouped the organisms by.
This is very hard to do. It took over a decade and a lot of work to explain the one trait of blue eyes in humans. That we cannot yet reverse engineer the exact sequences that give us our arbitrary classification of “species” isn’t a refutation of common descent but just our lack of skill in reverse engineering the genotype to correlate to the phenotype we have arbitrarily selected.
It may even be that our grouping by phenotype expression involves so many genetic sequences that it is computationally impossible but I’m confident that in time we’ll have a heuristic to automatically categorize a genome into a “species” using a small number of tags. This then finally eliminates the false dichotomy of creationist micro- verses macro- evolution as a species would be “Those sequences which the computer tags”.