The fossil record can't tell us anything about a mechanism- random mutaions & variations culled by natural selection, built-in responses to environmental cues, a carefully written genetic algorithm designed to bring about common descent, or a special creation for specific types of organisms.
It can't tell us if any alleged morphological similarities are due to convergent or divergent evolution. Nor can it tell us if the alleged lineage is just phenotypical plasticity of a population.
Genetic similarities can also be the result of convergence. Also we see similar proteins common in many organisms. These proteins have differences in nucleotide sequences allegedly due to random muations culled by NS. However even with the differences the proteins perform the same function (or no function at all, ie pseudo-genes)
Again there isn't any way to tell if the allged homologs are due to convergent or divergent evolution. Or if they are due to some design archetype.
Our arms and legs are very similar- femur to humerus; ulna/ radius to fiblula/ tibia; tarsals to carsals, etc., but no one is suggesting that the hind limbs evolved from the fore limbs or the fore limbs from the hind limbs.
Embryology and Evolution
Recently a college student wrote to the Creation Research Society asking about the status of embryology with relation to evolution because his zoology professor had presented the so-called Ã¢â‚¬Å“biogenetic lawÃ¢â‚¬Â to their class. This Ã¢â‚¬Å“lawÃ¢â‚¬Â states that as embryos develop they pass through the various stages attained by their ancestors as they climbed the Ã¢â‚¬Å“evolutionary ladderÃ¢â‚¬Â.
Considerations in Earlier Years
I empathized with this student because in the spring of 1947 when I was a freshman taking my first semester of zoology at the University of Massachusetts in Amherst, I had a similar experience. My professor, Gilbert L. Woodside, a HarvardÃ¢â‚¬â€œtrained embryology Ph.D. and then a leader in this field, presented to our class the embryology argument for evolution. Usually this concept is called recapitulation because the developing embryo is assumed to Ã¢â‚¬Å“summarizeÃ¢â‚¬Â or Ã¢â‚¬Å“epitomizeÃ¢â‚¬Â the entire history of its race. When certain embryonic observations are presented in a convincing way, the argument compels acceptance of a macroevolutionary sequence of animal or plant species. I recall thinking after that class, Ã¢â‚¬Å“How could anybody possibly doubt evolution when they understand this evidence?Ã¢â‚¬Â
I was driven to know more biology, and so I switched my major from psychology to zoology, taking physiology and entomology in my sophomore year. I had become a Christian while in the Navy before my collegiate education, but after two years at the university my Christian beliefs were being challenged in ways that were difficult to handle. I was slated to be a laboratory assistant in the physiology class the next fall, and would have enjoyed that greatly, but I transferred to a Christian college (Houghton in New York), majoring in zoology along with minors in Bible and in chemistry. I obtained a BA degree in 1950, and in the summer of 1951 a BS degree, also in zoology, from another Christian college (Wheaton in Illinois). In the latter I expanded my science and theology backgrounds. Then I taught science to middle and high school level students for one year at the Ben Lippen School which was then in North Carolina. In 1952 I returned as a graduate student to the University of Massachusetts where I obtained teaching and research assistantships.
Change of View
To my surprise I found myself in an experimental embryology course with Dr. Woodside, who now was Chairman of the Department of Zoology and of the Graduate School. I became captivated by Dr. Woodside and his field of embryology. I did research and wrote a masterÃ¢â‚¬â„¢s thesis on chick embryology and the first cancer-inhibiting drug, 8-azaguanine (see Frair and Woodside, 1956).
During my reading and research I became determined to plumb the depths of embryonic recapitulation, but to my utter amazement I learned from Dr. Woodside that the Ã¢â‚¬Å“biogenetic lawÃ¢â‚¬Â was dead! So the man who had convinced me of the importance of recapitulation when I was a freshman, then five years later was convincing me of the opposite. Dr. Woodside not only disbelieved it, but also he virtually despised it. Recapitulation no longer could be any more than a hypothesis at best, and he wanted me to have nothing to do with it.
Professor Woodside believed that embryology as a discipline was retarded because of recapitulation. He told me that by the mid-20th Century no informed embryologist could accept the recapitulation concept. Many investigators had given up their work in disgust because they ran into dead ends trying to fit their embryological data into an evolutionary context. Professor Woodside also believed that there had been only one Nobelist in embryology (Hans Spemann) because so many other good embryology investigators had been focusing on evolution and failing. An example of the many exceptions to the hypothesis of recapitulation is that in an evolution scheme the spinal cord is present before the brain, but in embryology the brain develops first. But, has not evolution been the thread that holds all of biology together? At least we knew 50 years ago, and still realize today, that Darwinian recapitulation is not part of any such thread (see Bergman, 1999; Wells, 1999a).