Major Transitions in Evolution
Life, a manifestation of replicating entities with heredity and variation, has flourished on planet earth over the last 3.8 billion years. It has expanded and diversified, occupying an ever greater range of habitats and utilizing newer and newer forms of resources. This has involved the evolution of ever more complex organisms, animal societies and biotic communities. This progressive elaboration of complex forms has been accomplished through a diversification of simpler entities, their aggregation and incorporation into higher level entities. This has entailed ever more sophisticated cooperative interactions, supported by a variety of group cementing forces: genetic similarity, central control, and synergy. Since every replicating entity has a tendency of producing more copies of itself, this results in a variety of conflicts at many levels, leading to manifestations such as the proliferation of junk DNA, parent-offspring conflict, and suppression of one human language by another. This saga of life on earth may be visualized as involving nine major transitions:
- Replicating molecules -to- Populations of molecules in protocells
- Independent replicators -to- Chromosomes
- RNA as gene and enzyme -to- DNA genes and protein enzymes
- Bacterial cells -to- Cells with nuclei and organelles
- Asexual clones -to- Sexual populations
- Single-celled organism -to- Multicellular animals, plants, fungi
- Organisms lacking nervous system -to- Animals with nervous system
- Solitary individuals -to- Colonies with non-reproductive castes. This evolutionary process has given rise to two other forms of replicating entities besides genes, namely, memes or behaviour patterns propagated through replication, and artifacts. The development of memes has led to the ninth major transition:
- Primate societies -to- Human societies with an elaborate symbolic language. The culmination of evolution of artifacts to the present day information and communication technology has brought us to the threshold of a tenth major transition:
- Language based human societies -to- Human societies with global access to entire stock of human knowledge.
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