Selection from Pyramids of Thrush Creek


          As Roger unpacked his things he noticed a spider in the planter of Venus flytraps.  He wondered if it had been there while Kathy was carrying it and imagined her reaction if she had seen it.  He watched as the spider crawled across an open pair of leaves and came in contact with the small hair-like sensors.  The leaves quickly snapped together, trapping the spider inside.  What an amazing plant, he thought.  Within the next few days the plant would secrete enzymes which would digest the spider and the nutrients would be absorbed by the plant.  He thought about the three unique features of the plant: the ability to sense the movement of a living organism on its leaves, the ability to move its leaves, and the ability to digest its prey. 

            All three of these features had to work together to produce one benefit, supplying the plant with added nutrition.  In his mind he compared it to the little pyramid of four stones along Thrush Creek.  The three unique features of the plant were the base stones which together supported the top stone, the beneficial nutrients.  Take away any one of the base stones and the top would tumble down.  He wondered how these three unique features evolved.  Which one came first?  No single feature by itself would provide any benefit to the plant.  What are the odds of the three features evolving simultaneously?  How could the process on natural selection produce such a plant?  He knew what Rick’s answer would be, but there had to be a more scientific explanation.  However, if the three features had developed toward a future benefit, that certainly would lend credence to Rick’s view of things.  He made a mental note to do some research on the question as soon as he had time.