Brown Algae and The Serendipity of Multicellularity

Thanks Dr. Hunter; I liked this part: "Instead of the expectation that multicellularity arose once and then proliferated, evolutionists now must say it arose independently several times. And instead of a sort of primitive multicellularity emerging and then undergoing evolutionary refinement, we must believe evolution first produced profoundly unlikely molecular machines, which then in turn enabled multicellularity." Here is a gem courtesy of Sal: How many different cells are there in complex organisms? Excerpt: The nematode worm Caenorhabditis elegans, the cellular ontogeny of which has been precisely mapped, has 1,179 and 1,090 distinct somatic cells (including those that undergo programmed cell death) in the male and female, respectively, each with a defined history and fate. Therefore, if we take the developmental trajectories and cell position into account, C. elegans has 10^3 different cell identities, even if many of these cells are functionally similar. By this reasoning, although the number of different cell types in mammals is often considered to lie in the order of hundreds, it is actually in the order of 10^12 if their positional identity and specific ontogeny are considered. Humans have an estimated 10^14 cells, mostly positioned in precise ways and with precise organization, shape and function, in skeletal architecture, musculature and organ type, many of which (such as the nose) show inherited idiosyncrasies. Even if the actual number of cells with distinct identities is discounted by a factor of 100 (on the basis that 99% of the cells are simply clonal expansions of a particular cell type in a particular location or under particular conditions (for example, fat, muscle or immune cells)), there are still 10^12 positionally different cell types. http://ai.stanford.edu/~serafim/CS374_2006/papers/Mattick_NRG2004.pdf bornagain77