Do unicellular organisms age?

Oliver Bogler obogler at
Wed May 31 14:28:11 EST 1995

In article <3qd1fe$bl5 at adelbert11.Stanford.EDU>,
cpatil at leland.Stanford.EDU (Christopher Kashinath Patil) wrote:

> Do unicellular organisms age? 
> It seems unlikely to me that unicellular organisms would age (as it would
> result in the extinction of clones that did undergo aging), but it also seems
> difficult to understand how certain kinds of age-related damage (buildup of
> metabolic by-products, etc.) could be avoided by these organisms.

I agree witht the first point - bacteria, for example, do not age as there
*must* be an unbroken chain of cells from the beginning of the bacterial
life to today. The germline of higher organisms can be seen similarly as
an "immortal" clone. (Immortal is in quotes because there was a heated
debate in this group about the appropriateness of using that word to talk
about cells - it is used purely in its narrow biological sense).

It is on the basis of this argument that it has been proposed that life
does not necessarily need to age. Ageing can then be seen as either 
1) a process that is not actively prevented in the somatic cells of
multicellular organisms, perhaps because that would be too metabolically
2) or as a process that is actively encouraged in the somatic tissue of
multicellular organisms to allow the turnover of generations that is
demanded by evolution.

> 2) Do all multicellular organisms age? If not, what is the complexity thresh-
> hold for aging?

Caleb Finches book describes senescence in some simple multicellular
organisms such as tetrahymena.

> "That in our day such giant shadows are cast by such pygmies only shows
> how late in the day it has become." -- Chargaff, referring to Watson & Crick

I love that quote!


Oliver Bogler
obogler at

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