LEARNING ENGLISH

Passage 12

Scientists at Michigan State University are asking a most challenging question. Can a computer program be considered alive? The members of the Digital Evolution Laboratory say yes. Computer scientists at the laboratory have created a program called Avida that has intrigued not only scientists and engineers but biologists and philosophers as well.

The Avida project began in the late 1990s, when Chris Adami, a physicist, sought to create computer programs that could evolve to do simple addition problems and reproduce inside a digital environment. Adami called these programs “digital organisms.” Whenever a digital organism replicates, it has a chance to alter the program of the newly created offspring. In this way, the programs mutate and evolve. The goal of the Avida program is to create a model that could simulate the evolutionary process.

Initially, the digital creations were unable to process numbers in any way. But Adami designed Avida to reward digital organisms that were able to work with the numbers in some way. The digital organisms that could process numbers were allowed to reproduce in higher numbers. In only six short months, the primitive program had evolved a number of mechanisms to perform addition. And, most surprisingly, not all of the digital creatures performed addition in the same way.

The Avida program now resides at Michigan State University, where it has been growing and changing for years. The digital creatures number in the billions and have colonized more than two hundred computers. The organisms compete with one another for resources, and the most successful ones are able to make more copies of themselves. Just like living creatures, the digital entities also undergo mutations. Mutations that are beneficial ensure greater reproduction; harmful mutations have the opposite effect.

As a model for studying evolution, the Avida project has been a great success. Adami’s digital organisms have suggested solutions to some of evolution’s biggest mysteries. For example, Avida has helped disprove the theory have suggested that some structures, such as the eye, are too complex to have been created in piecemeal stages. The evolution of Avida’s digital organisms proves that even extremely complex structures can be developed in stages over time.

The Avida program’s success has also raised some unintentional philosophical dilemmas. Does Avida just simulate evolution? Or are digital organisms a new form of life? According to the director of the Avida project, the processes undergone by the digital creatures are the same as those experienced by biological organisms. The only difference is that biological entities are based on strings of DNA, whereas the digital creations from Avida are based on strings of ones and zeros. In a living creature, different sequences of DNA instruct cells to create certain proteins. In one of the Avida creations, different sequences of computer code instruct the program to perform certain functions. In both cases, the reproduction of the organisms is subject to forces such as competition and mutation.

Now, some biologists are maintaining that the programs in the Avida project are alive. The programs live, die, reproduce, compete, cooperate, and evolve—activities that many biologists consider the hallmarks of life. One prominent biologist says, “They don’t have a metabolism—at least not yet. But otherwise, they’re alive.”

Of course, not everyone agrees that the program’s creations are alive. One difficulty is that biologists do not even agree on the definition of life. The diversity of life on Earth constantly surprises scientists, and there are simply too many characteristics and qualities to provide one simple definition of life.

Despite these misgivings, the directors of the Avida program remain optimistic that their program, even if not considered alive, is leading to a greater understanding of life in all its forms. It may even facilitate future searches for life on other planets. According to one member of the Avida team, “The problem that we have now is that we are focused on looking for DNA-based life. But there may be other kinds of life out there that we have never dreamed of.” The Avida program may provide biologists with another avenue to explore.
TOEFL-READING/Presentation: (DUE ON MONDAY JULY 25th, 2011)
Passage's purpose:
_____________________
Paragraph
a. What is the subject?
b. What are the main ideas?
Passage's main idea:_______________________

CÁC TIN KHÁC:
Passage # 4 7/4/2011 9:35:57 PM
Passage #3 6/29/2011 12:56:05 PM
Practice reading 6/2/2011 9:02:38 PM
1