RE: Evolution: Abrupt Changes
December 22, 2016 at 9:51 pm
(This post was last modified: December 22, 2016 at 10:10 pm by Anomalocaris.)
(December 22, 2016 at 9:18 pm)RiddledWithFear Wrote:(December 22, 2016 at 9:04 pm)Anomalocaris Wrote: Define abrupt.
Sudden, in this case sudden leaps from one "form" to the next.
(December 22, 2016 at 9:10 pm)ignoramus Wrote: Never heard it talked about like that...
http://phys.org/news/2013-02-species-sudden.html
Sudden? Over how many generations? You might find the so called 'sudden' change actually occurred progressively over a very large number of generations. tens of thousands. Admittedly many species may appear to change little over millions of generations, so speciation over ten thousand generations is abrupt compared to the period of stasis. But the process of speciation still takes place incrementally with little apparent change from generation to generation, but sufficient cumulative change over tens to hundreds of thousands of years.
The reason why species appear to remain little changed over many millions of years and then change significantly over hundreds of thousands of years usually have to do with stability of environment. When the environment is stable, species evolve into an relatively stable form In adaquate equilibrium to the environment. Once there, the species settle down into apparent stasis. Genetic motive force behind the change still occur at the same rate. But changes Now bring diminished possibility of further improvement in adaptation, but enhanced possibility of losing adaptation already achieved. So most changes are weeded out. The species over all appear to change little.
But if the environment changes, previously achieved adaptation losses their efficacy. Now change bring increased chance of improving adaptation. Improved adaptation gets selected, old obsolete adaptation does out. So specie overall appear to change.
When you have just a few fossils of a specie, so 50. The typical life of a mammalian species of 2 million years. This means on average your 50 specimens are from time slices 40 thousand years apart. Given this granualrity, a speciation event can indeed appear to us to be abrupt. Slightly older, and the specimen looked this way. For the last 49 specimens, the fossil all looked much the same. Next specimen, it changed so much it's probably a new species. Bang, abrupt speciation. Yes? No. remember there are probably 40 thousand years between specimens.
