What about the pace of evolution?

 

There are two theories about the pace of evolution. One believes that evolution occurs by accumulations of incremental changes over long periods of time. This is associated with gradualists and neo-Darwinism. Another theory proposed by Eldridge and Gould states that the fossil record shows very rapid spurts of change followed by long periods of stasis. This is known as “punctuated equilibrium”. Sympatric speciation from polyploids is likely a very rapid event in evolutionary context. A sudden geographical shift may also produce a very rapid change as well.

The debate is likely to flourish. Remember fossil records show external or skeletal changes, not internal organs. And fossilization is a rare occurrence.

 

Does evolution produce a perfect organism?

 

No. Nor does it have an “obligation” to do so.

 

Organisms are locked into historical constraints. Modifications are made on existing structures (Krebs cycle on top of glycolysis; PSII on top of PSI). Natural selection cannot rebuild existing structures; it adapts and co-opts structures. Selective pressure is applied to existing structures. Natural selection does not respond to future changes or aspirations of the individual.

 

“Here. Let me take your heart out and repair it while you wait” – that’s not going to happen.

 

Adaptation is about compromise. Versatility demands generalities. Unique abilities demand unique structures. A seal can swim very well, but walks very poorly. Can we really expect any animal to be able to do both exceedingly well?

 

We have wonderfully flexible hands and athletic bodies that are prone to sprains, torn ligaments, and dislocations. It’s the price we pay.

 

Not all evolution is adaptive. Alleles that are fixed by genetic drift are not always the best suited for that environment.

 

Wow, I survived that earthquake, but I and everyone around me is sensitive to peanuts.