THE CAMBRIAN EXPLOSION
I believe I can explain the Cambrian explosion. The Cambrian explosion refers to the appearance, in a relatively short space of geological time beginning more than 500 million years ago, of a very wide assortment of animals. I believe it came about through hybridization.
Many well preserved Cambrian fossils occur in the Burgess shale of the Canadian Rockies. These fossils include small soft bodied animals, several of which are plank tonic but non of which are larvae. Some of them seem to have the front end of one animal and the rear of another. Modern larvae present a comparable set-up; that is, larvae seem to be derived from animals belonging to groups different from those of their adult form. I have amassed a boxful of evidence that the basic larval forms did indeed originate as animals in other groups, and that such forms were transferred by hybridization. Animals with a larval stage are sequential chimeras” creatures initial whose body form, the larva, is followed by a distantly related form, the adult. I believe there are no true Cambrian larvae, only pseudo larvae, in which the initial form became the front end of the adult. Cambrian hybridizations produced concurrent chimeras, each made up of two distinctly related body forms.
About 600 million years ago, shortly before the Cambrian period animals with tissues made their first appearance. I agree with Darwin that there were several different forms of metazoan- Darwin suggested four or five and I believe they resulted from hybridization between various protists. All Cambrian animals were marine and like most marine today, they shed their eggs and sperm into the water where fertilization took place: Eggs of one species frequently encountered sperm of another species, and mechanisms to prevent hybridization would have been only poorly developed. Early animals had small genomes, which left their cells with plenty of spare gene capacity. These factors led to many fruitfull hybridizations, which result in concurrent chimeras.
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