A fascinating piece of research published a few days ago shed some light on how transitional fish/amphibians may have learned to walk on land as they moved from an aquatic to a terrestrial existence.
The researchers from the University of Ottawa, Canada, led by Emily Standen, took juvenile bichir (Polypterus senegalus) - a freshwater fish from Africa which has a primitive lung as well as gills and so can live on land - and raised them on land for eight months. The control group was raised in water as normal.
The land-raised bichir showed not only a noticeably more sophisticated style of walking but there were marked changes in the skeleton and musculature compared to the control group too.
What this illustrates is a basic principle of biology - a developing organism is 'plastic' in that its environment changes the phenotype so the final organism is not simply an expression of the genotype. This is not at all surprising since we know how things like health, nutrition and exercise can influence the development of human children - something implied in my earlier blog about melanoma, vitamin D and rickets.
It also shows how transitional fish could have become subject to selective pressures on land even before they had left their 'normal' aquatic environment. Those best able to survive on land and which were best able to develop a musculoskeletal system which facilitated survival there would have been differentially selected by the environment, so speeding up the transition to fully terrestrial existence and the evolution of limbs.
It must be so galling being a committed creationist and having to live with such clear evidence not only for evolution but such a clear illustration such as this of how it could have happened.
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