From: Annamalai Muthu (muthu@cs.washington.edu)
Date: Wed Dec 01 2004 - 02:16:42 PST
Paper Title: The evolutionary origin of complex features
One-line summary of the paper: The paper tries to explain the role of
various components of evolution in the building of complex features, with
the help of .digital organisms..
Main contributions of the paper:
-It has always puzzled me as to how humans had managed to attain such a
level of complexity in their structure. This paper uses a model
constituting of digital organisms to explain how certain complex features,
which provide immense benefit to the organism, evolve over time.
-The digital organisms (which are nothing but a sequence of instructions),
thrive by capturing energy from the environment to execute instructions
and replicate. Every time the sequence of instructions produces
meaningful functions, it is rewarded appropriately. This gives rise to a
form of competition between digital organisms. The good ones manage to
survive, while the bad ones die out. This competitive nature directs
evolution (mutation and replication) in the right direction.
-The paper shows how the EQU function (the most complex of them all)
evolves incrementally. First, the simpler functions are realized, then
they go on to build the more complex form.
Flaws:
-The paper presents a picture which claims that these digital organisms
can represent the natural evolution process very well. But I do not
agree. All organisms in the digital world live in an ideal world where
everyone is rewarded for being good, all organisms reside in the same
environment, the number of possible mutations is low and every organism is
very similar to the other organisms since it comes from the same set of 26
instructions. In the real world, the environment is not ideal, since not
all good organisms are rewarded, some good traits can go unrewarded. The
number of possible mutations is of the order of at least a few billion.
There are a variety of organisms in the real world, each type being
extremely diverse.
-Most complex organisms reproduce sexually, hence the applicability of
this idea might be greatly restricted.
Is this search???!!!
This can be thought of as search. The states constitute of the various
organisms put together, while the evaluation function used to guide the
search can be the fitness of the individuals in the population. The
operations used to get from one state to another are replication and
mutation. The goal state can be a variety of things, depending on the
required solution. It could be defined as one in which at least one
organism has reached a state of optimality. Alternatively, it could be
defined as one in which at least a certain portion of the organisms have
reached optimality. This search requires you to have great foresight,
because an immediate deleterious effect can have a good impact a few
generations down the line.
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