As we know the sudden appearance of most if not all phylum and basic body plans occurred in the Cambrian period. Did the instructions for these body plans come from nowhere or were there some sort of code that produces these. Despite the differences in form from the modern animals like Zebras to the Cambrian creatures, the Zebras basic body plan stems from the body plans that first appeared in the Cambrian period. So the developmental programs for these body plans must have been around from a very early time with the first creatures.
Perhaps it has been a case of the switching on and off of the particular genetic info for all body plan features to produce the different life forms ie limbs are similar despite whether they are fins of legs/arms so it is a case of a variation of the same basic body plan. As noted in embryology all life seems to develop along similar lines as though cast from the same mould and then will change in their fetus development according to that particular creature. This must have been in place from the start of when the first aquatic type creature existed and also before this if these body plans were produced relatively sudden in evolutionary terms in the Cambrian explosion.
According to this model, (a) the Universal Genome that encodes all major developmental programs essential for various phyla of Metazoa emerged in a unicellular or a primitive multicellular organism shortly before the Cambrian period; (b) The Metazoan phyla, all having similar genomes, are nonetheless so distinct because they utilize specific combinations of developmental programs. This model has two major predictions, first that a significant fraction of genetic information in lower taxons must be functionally useless but becomes useful in higher taxons, and second that one should be able to turn on in lower taxons some of the complex latent developmental programs, e.g. a program of eye development or antibody synthesis in sea urchin. An example of natural turning on of a complex latent program in a lower taxon is discussed.
http://www.tandfonline.com/doi/abs/10.4161/cc.6.15.4557#.VaEEzbUoTfc
Please refer to the above answer
Yet funny enough some say it was the Neanderthals that were stronger and more fit than modern humans. Anyway, I would have thought that even a smaller group could have survived and repopulated. But nevertheless, as many have shown small populations are more susceptible to the accumulation of harmful mutations and this perhaps caused their downfall in the end otherwise they could have replenished the population with time. They probably got many diseases and died out.
Yes, there is a lot of speculation in that article but it also mentions that Neanderthals suffered from diseases.
According to one study Neanderthals did carry harmful mutations and passed these on to modern humans when they interbred and we are still being affected by these though many have been eradicated out of the population. So this was probably a sign that Neanderthals were slowly dying out through many diseases as well due to their smaller populations and inbreeding.
The Neanderthal genome included harmful mutations that made the hominids around 40 percent less reproductively fit than modern humans, according to new estimates. Non-African humans inherited some of this genetic burden when they interbred with Neanderthals, though much of it has been lost over time. The results suggest that these harmful gene variants continue to reduce the fitness of some populations today.
Inbred Neanderthals left humans a genetic burden: Non-African human populations today have marginally lower fitness thanks to Neanderthal inheritance