I am a paleontologist interested by atavisms and retrograde evolution.
I found interesting indications in the l iterature concerning reverse evolution
in the limbs of snakes, eyes of ostracods, mandibles in collembola, wings in phasmids and ancestral digits of guinea pigs, but no explanations of those phenomena. Could you indicate me some papers about the origin of such retrograde evolutions?
thanks in advance and all the best
Dear Jean, I have written extensively about the use of cell biology in evolution (Evolutionary Biology, Cell-Cell Communication and Complex Disease. Wiley, 2012). The key to understanding morphogenesis has been the recognition that soluble growth factors and their receptors determine form and function……the same is true in phylogeny and evolution, though this concept is never applied in the evolution literature. Yet there are hints to this in Greg Gibson's writings (Gibson G, Reed LK. Cryptic genetic variation. Curr Biol. 2008 Nov 11;18(21):R989-90.) about cryptic variation and in the use of the term Ghost Lineage, which are correlative of the underlying molecular signaling that I am referring to. I am about to publish a paper, for example, explaining how pleiotropy and heterochrony can be understood mechanistically through this approach. John Torday
Heterochronous development (?) in cell cell communication. Meaning the time giving for a development is shifted in time for a given trait e.g. evolution of viviparity in Salamanders. Who knows?
I know that Heterochrony is a popular explanation for the evolution of novelty, but other than as a metaphor, I have never been able to get my head around what it meant until I started applying the principles of molecular embryogenesis. In that field, understanding the mechanisms involved in growth and differentiation remained descriptive until the late 1970s when George Todaro published a landmark paper showing that cells in culture secreted soluble growth factors. The discovery of the receptors for such growth factors on neighboring cells during embryogenesis provided the deep understanding of pattern formation. OK, now by applying such principles to Heterochrony, by 'rewiring' the cells producing the growth factors and the receptors you will generate changes in form and function over time…..and if those signaling mechanisms are constrained within any given structure- bone, lung, liver, kidney, brain- the modifications to the cell-cell signaling will come up with configurations more conducive to the environmental conditions that initiated them. Nowhere is that phenomenon more apparent than in the water-land transition, when specific gene duplications occurred under physiologic stress as vertebrates had to emerge from water on to land, or become extinct due to the drying up of bodies of water.
I hope that explanation of Heterochrony was helpful. If you have a particular phenotypic change of interest perhaps we could discuss how to use the ontogenetic/phylogenetic molecular approach, since it is only of interest if it is useful. For more information, please refer to the following.
1. Torday JS. Evolutionary biology redux. Perspect Biol Med. 2013
Autumn;56(4):455-84.
2. Torday and Rehan. Evolutionary Biology, Cell-Cell Communication and Complex Disease. Wiley, 2012.
3. Torday JS. A Central Theory of Biology. Med Hypotheses. 2015 Apr 4.
Valentin Krassilov, paleobotanist from Israel, is the author of term "retroconvergence" (there are some papers and chapters, particularly in the book "Evolutionary theory and processes: the modern horizons" dedicated to honour of Prof. Eviatar Nevo, 2004). In my book "Epimorphology and tectomorphology of higher fungi" (2010) the phenomenon of retroconvergency is associated to limited field of modules (hystiones) combinatorics.
Dear Jean Guex
Can you share with us the interesting facts about mandibles in Collembola that you mentioned?
Best regards,
Nikola
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