Bob Holmes at the New Scientist described the work of Dr. William Ratcliff and his colleagues at the University of Minnesota in St. Paul to select unicellular brewer's yeast that clump into a "snowflake" form as a model to study the evolution of single-celled organisms to multicellularity. After several hundred generations of selection, the yeast snowflakes began to show reproductive properties with some cells undergoing cell death to provide weak points for other cells to break off, allowing the snowflake to create offspring while leaving the clump strong enough to survive. S. Pelech points out that yeast like Saccharomyces cerevisiae are well known to naturally form pseudohyphal filaments depending on the nutrient conditions in their environment, so the formation of cell aggregates is already an inherent property of these types of fungi. The fact that some cells in Dr. Ratcliff's "snowflakes" die, most likely from competition for food and toxic products produced by neighbouring cells, is hardly a measure of cooperation amongst cells for the survival of the colony. Read More...

Tags: Evolution, Multicellular cell origin