Friday, March 29, 2013

CH9: Puncturing punctuationism




          Evolution is like slowly filling a bottle with water. You can constantly fill the bottle. Alternatively, you can quickly fill the bottle, stop for a while, and start filling again. Either way, in the end, the bottle is filled with water. For evolutionists, the former and latter approaches are referred to as  ‘gradualism’ (constant speed) and ‘punctuationism’ (variable speed), respectively. 


Gradualists and Punctuationists


          Gradualists believe that evolution proceeds constantly and slowly. Punctuationists, on the other hand, believe that evolution consists of two alternating periods. In an evolving period, things evolve significantly. In a stasis period, nothing evolves at all. 

Macro Mutation

          Macro mutation is a large scale mutation. The mutants would greatly differ from the original species. 

Saltation

Saltation is a type of macro mutation where big change (or jump) happen in one generation (sound like X-Men, isn’t it). Saltation is unlikely in nature. Here’re why:
  • Mutants are rare. They are usually seen as freaks. No one in the herd would want to mate with mutants. Mutants should become extinct in a few generations.
  • Big change cannot get to an optimal point, because it can easily step over the optimal point.
  • Saltation means a species arises by jumping directly to a particular position in a vast biomorph space. It is very difficult, since the space is astronomical.

Punctuationism’s View for Evolution

          Punctuationists believe that any large population resists change. There are two main reasons for this:
  • Genes in every original individual are already working in corporation. There is no need to welcome a new gene to  the new corporation and create a mutant.
  • The group of mutants will be kill to extinction. The mutants evolve from the original population, and tend to have similar way of life. The original and mutated populations therefore tend to compete rather than co-exist. They will kill each other until one of them  becomes extinct. 
          But these two reasons are not always true. If the organism really resists changes, we should see difficulty in genetic engineer. But so far, we don’t see much. For example, we can selective breed cows to have more milk without difficulty.

Paleontologist and Evolutionists

          Paleontologists are closely related to evolutionists. They both attempt to find out what happens in the distant past.  While paleontologists study about fossil, evolutionists use fossil to deduce clue about evolution. 


Fossil, Gradualism, and Punctuationalism

          Fossil is one evidence gradualists and punctuationists use to support their stand point. The fossil record is incomplete. We do not have fossil of all species in this world. There are few reasons for this. First, not all species (e.g., those with no bone structure) can fossilized. Also, bone must be in a very special condition in order to fossilized. Next, perhaps, not all fossils have been discovered. 
Gradualists argue that if the fossil record was complete, we should see a very smooth evolution of all the species. We should see the species evolving inches by inches. 
“Something like the transition from Amoeba to man, he pointed out, goes on in every mother's womb in a mere nine months.”
          Punctuationists, on the other hand, argue that the fossil might not be as incomplete as we thought. The evolution is, by nature, not continuous. Therefore, we should not expect to see smooth evolution from the fossil record.  

Modern Punctuationism, Saltation, and Catastrophism

          These three schools of thoughts are the opposite of gradualism. Modern punctuationism believes that evolution happens only for a brief period immediately after an event. The word “brief” is in geological time which means tens of thousand of years. This brief period is followed by a stasis period, where there is no evolution at all. 

“The origin of a new kind of animal in 100,000 years or less is regarded by paleontologists as sudden or instantaneous.”

          Saltation believes in jump evolution where a mutation can happen in a single generation. Finally, catastrophism believes that catastrophe causes mass extinction and creation of new species. 

“You cannot do history by selective quotation and search for qualifying footnotes.” 

Speciation

          Speciation is a study of how a new species come to existence. Tigers and Lions are similar in some sense. They must share the same ancestor in a distant past. But how do they turn out to be two species?


How Difficult is Speciation

Think about it. It’s rather difficult to have a new species. If a saltation really happen, the new species would not be able to find a mate. Even if two species would like to mate, they won’t be able to create offspring due to biological incompatibility. 
Also, the new species would not coexist with the original species. They will compete. They will kill each other until one of them has gone extinct. After all, you can’t imagine see tigers and lions live together happily ever after. 

“It is a widely accepted principle of ecology that two species with the same way of life will not coexist for long in one place, because they will compete and one or other will be driven extinct.”

Geographical Isolation

         One theory for speciation is geographical isolation. At the beginning, two species might be just one species. Then, somehow, a part of the species might have migrated to a new location. And, there must be geological condition to prevent the emigrants to return to the original herd. 
From that point, two groups of the same species evolve separately. After some time, they become two species which look quite different from each other. More interestingly, the migrated species may return to the original place and drive the original herd extinct. 

Fooled by Geographical Isolation

            Suppose we dig at the place where the original herd lived. We shall see fossil of both original and migrated species. We can see that the owners of these fossil share similar traits, and we must have concluded that they would share the same ancestor in the distant past. This is quite correct. 
                 But, we might be fooled when moving a step further. When we might have concluded that the big difference in two species is because of ‘jump’ evolution. What we forgot to factor in is ‘geographical isolation.’ If we do, we should have concluded that fossils are jerky, because of migration, not because of evolution. We just dig at the wrong place. 

Summary of Rate of Evolution

We can classify all evolution schools of thought based on the rate of evolution:
  1. True saltation: Mutation takes place in one generation
  2. Gradualism, i.e., anti-true-saltation
    1. Constant speedism: Evolution proceeds at a constant speed. No evolutionists today believe in this.
    2. Variable speedism: Evolution proceeds but not necessarily at the constant speed. There are two types:
      1. Discrete variable speedism: The rate of evolution at a particular time can be one of several values. In the view of punctuationists, the rate can be either top-gear evolution or
      2. Continuous variable speedism: The rate of evolution can fluctuate to any value. From this point of view, stasis is just a state with very low evolution speed.
 ---------------------------------------------------------------------------------------------------------
Book or Audiobooks?

Personally, I prefer audiobooks. It's fun, and I can listen when I'm doing something else. It also makes other activities (e.g., jogging) a lot more fun. For more detail about audiobooks, please read [this post].

There is one more reason that may encourage you to go for the audiobook version. You can get it now for FREE. Audible offers you a free trial for 14 days. Even if you get the book and cancel the subscription right away (so that you don't have to pay), you can keep the book. And, don't worry if you lost the audiobook file. Just log into audible.com. You can keep downloading the over and over again.
About the summary: It takes time to finish up a book. And, when you do, sometimes, you want to review what you learn from the book. If you do not make  notes as you read, you might have to go through the book once again. This can be time-consuming when you are dealing with a book. But you can still flip through the book and locate what you are looking for.

However, when the material is an audiobook, it is extremely hard to locate a specific part of content. Most likely you will have to listen to the entire audiobook once again.

This book summary will help solve the pain of having to go through the book all over again.

I am leaving out the details of the books. Most books have interesting examples and case studies, not included here. Reading the original book would be much more entertaining and enlightening. If you like the summary, you may want to get the original from the source below.

No comments:

Post a Comment