Category Archives: life

Thinking About Life

When I told you there is no consensus on a definition for life, you don’t need to take my word for it. Just check out wikipedia!

It is still a challenge for scientists and philosophers to define life in unequivocal terms.[11][12][13] Defining life is difficult —in part— because life is a process, not a pure substance.[14] Any definition must be sufficiently broad to encompass all life with which we are familiar, and it should be sufficiently general that, with it, scientists would not miss life that may be fundamentally different from earthly life.[15]

Since there is no unequivocal definition of life, the current understanding is descriptive, where life is a characteristic of organisms that exhibit all or most of the following phenomena:[14][16]

I always keep this fact in mind anytime someone tries to extract too much significance out of the fact that it is likewise difficult to define things like ‘design’ and ‘intelligence.’  An attempt to build an argument around a selective demand for precise definitions is a sign that the attempt is rooted in a biased agenda and not an open-ended investigation.

But let’s get back to the descriptive criteria used to identify life.

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What is Life?

Biologists find themselves in the uncomfortable position of studying something that is difficult to define. Traditionally, they define life by listing several features characteristic to life, including metabolism, growth and development, responsiveness, and reproduction. Because of its central importance in evolution, many emphasize reproduction. Yet Daniel Koshland tells this story:

What is the definition of life? I remember a conference of the scientific elite that sought to answer that question. Is an enzyme alive? Is a virus alive? Is a cell alive? After many hours of launching promising balloons that defined life in a sentence, followed by equally conclusive punctures of these balloons, a solution seemed at hand: “The ability to reproduce–that is the essential characteristic of life,” said one statesman of science. Everyone nodded in agreement that the essential of a life was the ability to reproduce, until one small voice was heard. “Then one rabbit is dead. Two rabbits–a male and female–are alive but either one alone is dead.” At that point, we all became convinced that although everyone knows what life is there is no simple definition of life. [1]

Koshland himself defines life by citing seven features that are both universal and essential to life: “P(rogram), I(mprovisation), C(ompartmentalization), E(nergy), R(egeneration), A(daptability), S(eclusion), PICERAS, for short–are the fundamental principles on which a living system is based.” [1] That life resists attempts to define it in an efficient and simplistic manner may speak to manner in which reductionism fails to account for it.

In 2001, Bernard Korzeniewski used a cybernetic approach to come up with a definition of life that turns out to be quite helpful when thinking of evolution as a process that was designed.

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What is Life?

Peter Macklem has written a very interesting short article that many readers of this blog might enjoy

Here are a few excerpts with some follow-up questions to think about.

Life’s order is characterized by emergent phenomena. These I define as the spontaneous development of self-organized order among ensembles that can neither be predicted nor explained by examining component parts in isolation. Spontaneity and self-organization mean that no external agent is sculpting the organism: it sculpts itself. Ensembles mean that an emergent system is composed of many parts. And for the component parts to self-organize, they must intercommunicate, interact, and cooperate. Life provides many interconnections: hormones, nerves, gap junctions, cytokines, and so forth. Thus understanding emergence requires studying the behavior of integrated networks. Reductionism cannot solve the secrets of emergence.

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