Science 20 September 2013: Vol. 341 no. 6152 pp. 1355-1356 DOI: 10.1126/science.1239450
- Perspective / Earth Science
Causes of the Cambrian Explosion [subscription required] by M. Paul Smith and David A. T. Harper
Excerpt: “The rapid diversification of animals in the early Cambrian is likely to have been the result of a complex interplay of biotic and abiotic processes (see the first figure).”
My comment submitted to the Science site on 9/20/13 and approved on 9/24/13.
Thank you. There is now no question that the abiotic to biologically-based origin of the cascade involves the ability to acquire nutrient chemicals and to construct ecological niches. Ecological niche construction leads to social niche construction via the metabolism of nutrients to species-specific pheromones, which also control reproduction in all species. (Yes, even in birds.)
Ecological and social niche construction clearly lead to morphogenesis and neurogenic niche construction exemplified in nematodes that developed teeth in the transition from bacterial “grazing” to predation. Nutrient-dependent pheromone-controlled adaptive evolution then appears to be responsible for the earliest forms of socio-cognitive niche construction exemplified in brainless learning and memory.
Thus, the basis for the Cambrian explosion can be linked to an environmental drive that evolved from that of nutrient ingestion in unicellular organisms to that of pheromone-controlled socialization in insects sans mutations. In vertebrates we can see the progression from neurogenic niche construction in nematodes to construction of the invertebrate socio-cognitive niche, which reaches its pinnacle in mammals.
In mammals, food odors and pheromones epigenetically effect changes in hormone-organized and hormone-activated behaviors via hormones such as gonadotropin releasing hormone, luteinizing hormone and their downstream developmental affects on pheromone-controlled sexual behavior in nutrient-dependent reproductively fit individuals across species of vertebrates (Yes, again, even in birds.) Thus, the epigenetic effects of the sensory environment are linked to genes, behavior, and back via genetically predisposed species-specific behaviors that involve the physiology of reproduction.
Thanks again. The authors make no mention of mutations or any aspect of what might otherwise still be considered by evolutionary theorists to be mutation-driven evolution. Evidently they are aware of the experiments and recent report that mutations are not fixed in nematodes, which is why I mentioned the transition to predatory nematodes that clearly involves nutrient-dependent pheromone-controlled fixation of new alleles, not mutations.
Apparently, we can no more get to the Cambrian explosion via mutations than we can get to construction of our socio-cognitive niche without the central role of nutrient-dependent pheromone-controlled reproduction. That makes sense, doesn’t it?