Bacteria are very complex and I don't think anyone would suggest that they could "randomly appear".
The meteorite you are talking about is one from Mars. If such traces could be confirmed to be fossils (and the general consensus appears to be that they are not) then they would have come from Mars after the appearance of life there in a process, presumably, similar to one here.
Well where did that bacteria come from? I'm not trying to nudge the creationists to put there input in, but I just want to know what scientific explanation there is to explain the appearance of early bacteria.
------------------ "The only thing necessary for the Triumph of Evil is for Good Men to do nothing."- Edmund Burke
Actually 'nannobacteria' have been found in at least three different meteorites that I'm aware of, only one of which (ALH84001) is from Mars. And yes, that they actually are/were living things is a rather unpopular opinion in the scientific community, especially amongst biologists.
If they can be grown in culture that should settle the issue permanently.
quote:Uh, these are, at best, fossilized bacteria.
And in the case of the Martian rock that caused such a stir a few years ago, they're not even that.
Instead, they're magnetite crystals that we tend to find in certain bacteria here on earth.
In other words, it would be as if you found some hydroxyapatite and noting that since we find this material mostly in bones and teeth, that must mean that the hydroxyapatite came from a living creature. It's a huge jump, especially if, as in the case of the magnetite crystals found on the Martian rocks, there is a tremendous difference in scale between what we found and what shows up on Earth (if I recall correctly, the crystals on the Martian rocks are so small that, if we assume a consistency in size between bacterium and crystal, the Martian bacteria would be the smallest organism ever encountered.)
Ned, I was talking about culturing "nannobacteria" allegedly found in human aortas, human cataracts, springwater, mammalian blood, espresso machines and the water-supply pipes of the greater Austin area--that would presumably be alive right up until the point you plant them in a vacuum and gold-plate the buggers. Mea culpa, I worded my message ambiguously.
[This message has been edited by gene90, 02-24-2004]
Why do people consider bacteria to be 1. representative of the first replicators on Earth 2. primitive or unevolved?
Unless one is a panspermia adherent (which only pushes the location of abiogenesis somewhere else but not the root mechanism), bacteria are far to developed to have been the original products of abiogenesis. That would require a creationist leap in illogic.
Second, of all the lifeforms on the planet, bacteria are the easiest to follow many thousands of generation of morphological and molecular evolution. It is startling how quickly one can observe the accumulation and fixation of adaptive mutations under different environmental stresses in bacteria for example
Cooper VS, Bennett AF, Lenski RE. Evolution of thermal dependence of growth rate of Escherichia coli populations during 20,000 generations in a constant environment. Evolution Int J Org Evolution. 2001 May;55(5):889-96.
Given that within a few weeks one can observe tremendous change in the genetic composition of bacterial populations, why would anyone expect modern bacteria of any species to resemble in any way, bacteria from hundreds, thousands, millions or billions of years ago?