[tatumizer]

Do you know that MANY cells in our body are not replaceable? E.g. those that control muscles. If this cell dies, the man dies, it's that simple. BTW, bacteria (=~cell) intelligence is an active area of research (google it, you will be surprised). That's the only form of intelligence we know. Apparently, we are not familiar with the most intelligent ones yet - they (certain species) may have very developed knowledge of things, including the art of DNA manipulation, which goes far beyond everything ME-cell (=human) knows. Why assume we are the brightest ones? It's laughable.

[yohui]

As someone with a modicum of biological knowledge, I am not aware of any single cell that is critical to human survival in the way you describe.

As for your analogy, it is true that microorganisms can perform wonderful feats, but it is a bit misleading to equate that to general intelligence. It is like saying a compiler is smarter than a programmer, because its design incorporates tricks the human may not know. (The bacteria being "designed" by the trial-and-error process of natural selection, rather than an intelligent entity, of course.)

[tatumizer]

Of course? It's the same kind of "of course" as heavy objects fall faster than light ones. Because Aristotle said so.