MadSci Network: Evolution |
Great question! If life did originate by natural, trial-and-error combinations of organic chemicals, it is likely that its enzymatic effeciency was very poor, at first. If no other life is present, even an inefficient, weak enzyme would always win, since it is the sole enzyme (or cell). However, such a primitive biochemical metabolism could not compete against the ultra- sophisticated, fast, efficient enzyme capabilities of modern bacteria. Once you get some background into marine ecology, it will be clear that the competition for nutrients (nitrate, phosphate, iron, vitamins etc.) is fierce, and competitive exclusion is common. (For example, now that the silica input into the Black Sea has been interrupted by dams on the Danube that hold back the sandy sediments that once entered the Black Sea, the phytoplankton community has been totally changed: the silica-dependent diatoms have been replaced by the slower-growing dinoflagellates that do not require silica.) Another way of thinking about this is to use an human analogy: a young inventer like Alexander Graham Bell, working in his workshop in Nova Scotia, couldn't invent the telephone and start up a company that could successfully compete against ATT (unless a fundamentally different technology was involved, like the internet). In the case of life on earth, there seems to be only one basic type of biochemistry, so life cannot originate a second time, unless all life is first extinguished.