Summary of Today's Topic

      Last time in class we discussed the origin of life on Earth in a naturalistic way. Under natural law, how did life evolve? How did intelligence evolve? It was understood that the progression of evolution began with molecules and was governed by the laws of chemistry. But the evolution of intelligence was more of a grey area that is not as clear as the laws of more empirical subjects such as chemistry and physics.

     As scientists learned more about the complexities of evolution, genetics and biology, the chances that life similar to Earth could evolve on another planet seemed less probable. Pessimests like Dobzhansky said the chances of a similar evolutionary process on another planet producing human-like life is zero. Optimists like Carl Sagan aruged that the paths need not by identical to produce a similar result. 

Simpson

     The overall context of this article was the space program was revving up, taking place around the same time as the Mariner/Viking missions. Simpson, a professor of Zoology, was one of the more prominent evolutionary theorists of the mid 20^th century. Simpson was mostly interested in the biological aspect of the evolution of life on Earth. Simpson said there were 5 distinct stages of emergence of intelligence:

1)      Chemical Evolution: the formation of building blocks

2)      Cellular Formation: the creation of metabolic and genetic systems

3)      Intermediate Evolution: the evolution from single celled organisms to multi-cellular organisms

4)      Biological Evolution

5)      Emergence of Intelligence

Simpson claims that the probability of such things happening decrease as you go down his stages of evolution. Simpson was very pessimistic of the idea that the species and intelligence we find here on Earth can be replicated elsewhere.  Simpson's argument is similar to Wallace's regarding the fact that evolutionary theory is not linear or directed but is more like a branching tree.  Neither believe that the same branching can occur twice and thus it is unlikely that  humanoids or any other type of inteligent life will evolve again.  This is because evolution is contingent, meaning that it depends upon specific events occuring at a specific time.  Due to this view on the prospect of extraterrestrial life Simpson does not feel that it is even practical to attempt to communicate with extraterrestrials.  He states that even if there were other intelligent beings in the universe, they would have to be living so far away that by the time they recieved a message from us, we and/or they would most likely be dead. Therefore no communication could actually take place.

Gould

     To blunt Simpson’s pessimism Stephen J. Gould mentions convergent evolution, size of universe, and having a sample size of one. Convergence happens when characteristics of organisms are similar in function without having a close common ancestor--metaphorically speaking, a specific characteristic can emerge on two different branches of the “evolutionary tree”. The argument for the size of the universe is one we have seen many times before: the gigantic scale of the universe seems to "cancel out" Simpson's low probabilities of intelligence emerging. Finally, Gould points out that statistically, having a sample size of one (the Earth) is not sufficient enough to extrapolate a trend out and generalize it towards the universe.

Key Terms & People

Humanoid: having the physical form and intelligence that resembles Humans

Deterministic View: Chemists and Physisists have a deterministic view, the outcome of a system is determined by the conditions that are present in the beginning. If you go back to the beginning, under the right conditions intelligence will come out again

Opportunistic View: Biologists have this view, intelligence and the species as seen on the Earth are not replicable. Rewind the tape and the outcome will not resemble what we see today

Convergent Evolution: the appearance of apparently similar structures in organisms of different lines of descent. The adaptive evolution of superficially similar structures, such as the wings of birds and insects, in unrelated species subjected to similar environments.

Relevant Links

http://library.thinkquest.org/C003763/index.php?page=origin03

http://www.pbs.org/wgbh/evolution/library/06/2/l_062_02.html

http://www.snotr.com/video/128

Answer the question!  http://wiki.answers.com/Q/What_is_the_difference_between_chemical_evolution_and_biological_evolution