Lantog wrote: Everything we’ve learned from developmental biology and comparative genomics in the last decade is consistent with extant body plans being derived by descent with modification from simpler ones…
That question is the center and core of dispute between evolution and design. No wonder, this question keeps the debates and disputes alive, because we have not yet a clear and fully elucidated picture. In order to know what provokes the origin of body plans, and if the claim that evolutionary mechanisms might explain biodiversity, and the change from one kind or species to another, and the formation of evolutionary novelty, like eyes, wings, legs, finns, ears etc. we need to know first what ontogenetic mechanisms and forces actually provoke body forms. Paul Nelson has not lied in regard of stating that mainstream science has been greatly ignorant to point out clearly what mechanism that is.
EVEN PROPONENTS OF EVOLUTION ADMIT TO NOT KNOWING HOW EVOLUTION SUPPOSEDLY WORKS:
No coherent causative model of morphogenesis has ever been presented.
“Although the vast majority of research in evolutionary biology is focused on adaption, a general theory for the population-genetic mechanisms by which complex adaptations are acquired remains to be developed.”
Proceedings of the National Academy of Sciences of the U.S., “Scaling expectations for the time to establishment of complex adaptations”, September 7, 2010, doi:10.1073/pnas.1010836107.
“Students should realize that although virtually all scientists accept the general concept of evolution of species, scientists do have different opinions on how fast and by what mechanisms evolution proceeds.”
The American Association for the Advancement of Science, Educational Benchmarks, (F) Evolution of Life
“Scientists are still uncovering the specifics of how, when, and why evolution produced the life we see on Earth today.”
Smithsonian’s National Museum of Natural History’s website, “Foundational Concepts: Evolution” page
“But they are trying to figure out how evolution happens, and that’s not an easy job.”
University of California Museum of Paleontology and the National Center for Science Education
“Much of the recent experimental work on natural selection has focused on three goals: determining how common it is, identifying the precise genetic changes that give rise to the adaptations produced by natural selection, and assessing just how big a role natural selection plays in a key problem of evolutionary biology—the origin of new species.”
Scientific American Magazine, “The Evolution of Evolution: Testing Natural Selection with Genetics”, December 18, 2008.
Science however goes forward, and keeps elucidating what goes on inside the cell, and development biology is opening the black box, and demonstrating how organisms develop. We are slowly getting out of a state of ignorance in regard of what mechanisms determines cell shape, assignment of their planes of division, tendencies to move, directions and rates of movement, modes of differentiation into particular cell types, and cell death (apoptosis).
Two reasons :
One primary feature of oriented cell division is the proper positioning of the mitotic spindle relative to a defined polarity axis. In principle, spindle orientation is achieved through signaling pathways that provide a molecular link between the cell cortex and spindle microtubules. These pathways are thought to elicit ( provoke ) both static connections and dynamic forces on the spindle to achieve the desired orientation prior to cell division. Although our knowledge of the signaling molecules involved in this process and our understanding of how they each function at the molecular level remain limited, collective efforts over the years have shed light on the importance of spindle orientation to animal development and function. Moreover, emerging evidence shows an association between improper spindle orientation and a number of developmental diseases as well as tumor formation.
and: Electrical gradients and fields are critical in the 3D function and shape of cells and organs.
Electrical signaling is key for cells to properly interpret their environment, and when this process goes awry, the cells default to a cancer program.
While ion flows control cell-level behaviors such as migration, differentiation, and proliferation, bioelectric signals also function as master regulators of large-scale shape in many contexts: a simple signal can induce complex, highly orchestrated, self-limiting downstream morphogenetic cascades. For example, an unmodulated flux of protons can cause the formation of a complete tail of the right rise and tissue composition.
BOTH EXPLANATIONS POINT TO INFORMATION. INFORMATION IS THE KEY. CHANGE THE INFORMATIONAL INSTRUCTIONS, AND THE RESULT IS NOT NEW BODY PLANS, BUT DESEASE, CANCER ETC. IN THE END, THE QUESTION IS: WHERE DOES THE INFORMATION COME FROM THAT DIRECTS THE FORMATION OF NEW BODY PLANS ?
And a second question arises : Why the heck would unicellular protozoans want to evolve into multicellular organisms, if they compartmentalize and are able to work with multiple organs which exercise various tasks just fine, like multicellular organisms do ? As for example : Diplodinium (Epidinium) ecaudatum, which has a kind of "brain" (motorium); 2 - - mouth; 4 - conductive filaments of the pharynx; 5 - fibrils pharynx; 6 - skeletal plate; 7 - endoplasm; 8 - "hindgut"; 9 - poroshitsa; 10 - contractile vacuole; 11 - Ma;Mi-12; 13 - dorsal lip; 14 - dorsal cirri area ???