Why Didn't They Grow Up?

[seer]

I have been reading about bacteria. It seems that over millions or even a billion years that they have remained quite stable, there may have been minor changes but some, it seems, never changed into anything else.

An example:
http://www.ucmp.berkeley.edu/bacteria/bacteriafr.html

The picture above is a short chain of cyanobacterial cells, from the Bitter Springs Chert of northern Australia (about 1 billion years old). Very similar cyanobacteria are alive today; in fact, most fossil cyanobacteria can almost be referred to living genera. Compare this fossil cyanobacterium with this picture of the living cyanobacterium Oscillatoria. The group shows what is probably the most extreme conservatism of morphology of any organisms.

How come these never evolved, how could it be that many bacteria remained relatively the same over all this time. That the bacteria we have today hasn't long ago changed into something else?

[phank]

Selection. There are certain niches in the environment which support different lifestyles. Larger (multicellular) organisms can fill some of them, and sure enough some single-celled organisms DID evolve. Probably the key invention was the eukaryotic cell.

But really, asking why all bacteria didn't become something totally different is kind of like asking why there is still traffic on side streets even after the interstate highway system was built. If some organisms are ideally suited for some unchanging habitat, what's to select?

Now, maybe the question you're asking has to do with drift? One would expect mutations in these bacteria for all the usual reasons, one would expect a great many of those mutations to be neutral, and statistically one would expect a good many neutral mutations to reach fixation just because they fall at the far end of the drift curve. And I think the answer to this question refers back to the "conservatism of morphology". NOT conservatism of genetics or DNA, just morphology. The modern versions look like and live like the old versions. At the molecular level they're probably quite different just through drift.

[oxmixmudd]

I have been reading about bacteria. It seems that over millions or even a billion years that they have remained quite stable, there may have been minor changes but some, it seems, never changed into anything else.

An example:
http://www.ucmp.berkeley.edu/bacteria/bacteriafr.html



How come these never evolved, how could it be that many bacteria remained relatively the same over all this time. That the bacteria we have today hasn't long ago changed into something else?

One of the most common missses from creationists is to thing about evolution as a serial process rather than a parallel process.

The short answer seer is that some populations of them did evolve. But others did not.


Jim

[seer]

The short answer seer is that some populations of them did evolve. But others did not.

Jim

Ok Jim, so some species, like the one linked - never really evolved. So not all creatures evolve?

[wattsr1]

I have been reading about bacteria. It seems that over millions or even a billion years that they have remained quite stable, there may have been minor changes but some, it seems, never changed into anything else.

An example:
http://www.ucmp.berkeley.edu/bacteria/bacteriafr.html



How come these never evolved, how could it be that many bacteria remained relatively the same over all this time. That the bacteria we have today hasn't long ago changed into something else?

That's a bit like asking - how come people in southern Australia are dressing in thick, heavy clothing, when people in Florida are running around in thin, skimpy clothing.

Different environments mean that different things happen to people. Southern Australia is in the grip of winter. Florida is in the grip of summer. There is no pressure in Florida for people to wear thick heavy clothing. There sure is here in Oz.


So, if 99.999999% of bacteria remain in environments where there is no pressure on them, why would they change - other than by random genetic drift?

[phank]

Ok Jim, so some species, like the one linked - never really evolved. So not all creatures evolve?

All lineages evolve. No individual organisms evolve, since evolution applies only to change from generation to generation. And evolution doesn't necessarily mean major morphological change over time, although it CAN happen, and occasionally has happened. But failure to change form or lifestyle isn't the same thing as failure to evolve.

[Jorge]

I have been reading about bacteria. It seems that over millions or even a billion years that they have remained quite stable, there may have been minor changes but some, it seems, never changed into anything else.

An example:
http://www.ucmp.berkeley.edu/bacteria/bacteriafr.html



How come these never evolved, how could it be that many bacteria remained relatively the same over all this time. That the bacteria we have today hasn't long ago changed into something else?

************************************************************

When you do a thorough search of the literature, the answers to your question that you will find are as preposterous as they are imaginative. I've read many such answers and the bottom line to all of them is this :

NO MATTER WHAT YOU ASK ABOUT EVOLUTION, through creative just-so stories the Evo-Faithful will always -- I mean ALWAYS -- have an answer. They can answer why things change and why they stay the same ... why "evolutionary-advantageous" things happen and why "evolutionary-advantageous" things do not happen. They can answer the thesis and the antithesis. They can answer the Ying and the Yang. The Evo-Myth answers all!

That's why I ceased exploring lines of reasoning such as the one you raise here - heads they win, tails you lose.

End of my input here. Hope you learned something (if not, you will end up wasting lots of your time).

Jorge

[seer]

So, if 99.999999% of bacteria remain in environments where there is no pressure on them, why would they change - other than by random genetic drift?

But most of these bacteria, like the Cyanobacteria in the link, are pretty much universal. So why didn't these various environments create the necessary pressures to change them into a different species?

[wattsr1]

But most of these bacteria, like the Cyanobacteria in the link, are pretty much universal. So why didn't these various environments create the necessary pressures to change them into a different species?

How do you know they didn't?

Clearly the fact that the bacteria inhabit those environments means that they are to some degree adapted. But how do you know that there was no change?

[Tiggy]

But most of these bacteria, like the Cyanobacteria in the link, are pretty much universal. So why didn't these various environments create the necessary pressures to change them into a different species?

Why should they? Just because something can happen doesn't mean it must happen. You may as well ask "why don't I get 6-6 every time I roll a pair of dice?"

- T

[seer]

How do you know they didn't?

Clearly the fact that the bacteria inhabit those environments means that they are to some degree adapted. But how do you know that there was no change?

Well according to the article there was really no change in morphology. No one knows what their internals were like, but considering that they were relatively simple animals I doubt that the internals changed much either. One would think that any significant change within the internals of such a simple creature would have presented itself in real morphological change.

[seer]

Why should they? Just because something can happen doesn't mean it must happen. You may as well ask "why don't I get 6-6 every time I roll a pair of dice?"

- T

Ok, so not all species evolve - fine.

[Tiggy]

Ok, so not all species evolve - fine.

All species keep evolving over time; that is the nature of the imperfect genetic copying process. But not all change their morphology.

- T

[lao tzu]

The following is a repost of a response I made to a muslim creationist a few years back. It seems especially relevant considering the OP's reference to the unchanging characteristics of cyanobacteria.



I've read your comments about a "bacteria remaining a bacteria." As bacteria represent the vast majority of diversity of life on this planet, not to mention ninety percent of the earth's biomass, this statement, as popular as it seems to be in creationist circles, reflects a profound disconnect from the actual science.

The genetic differences in the realm of bacteria dwarf anything we can find in the macroscopic world. As they are also the most primitive organisms, and thus have had the longest time to evolve, this is to be expected.

While we could show the evolution you're asking for by looking at mitochondria, I'm going to concentrate on plastids, a fundamental component of all plant life, as I've got the review paper describing their evolution in front of me. Plastids, like mitochondria, are an example of a "bacteria becoming an organelle." The paper is from 2005, "Changing concepts of a plant: current knowledge on plant diversity and evolution," by Isao Inouye and Noriko Okamoto.

See the animated attachment, derived from a figure in the above paper.



The organism pictured is in the phylum cryptophyta, and beyond the presence of mitochondria, the picture shows they are an example of an extra-ordinary evolution of bacteria into plants through a process called secondary endosymbiosis. Endosymbiosis means a separate organism has been incorporated into the first; secondary endosymbiosis means an organism that has accomplished this task is then incorporated into a third, yielding organisms like cryptophyta.

Unlike ourselves, bacteria have far more flexible means of evolution, at a relatively much larger scale. Endosymbiosis is an example.

Cryptophyta derive from the endosymbiotic incorporation of rhodophyta (red algae), themselves deriving from the endosymbiotic incorporation of cyanobacteria, the most primitive organisms capable of photosynthesis. The remnants of this ancient process are literally visible in the separate cell membranes we can see in the diagram. This is the "ultrastructural evidence" you'll find in the literature. The remnants are called "plastids."

From Inouye/Okamoto, "Plastids are formerly independent photosynthesizing organisms that were integrated into eukaryotic cells via a temporary symbiont, eventually becoming a permanent organelle."

On another branch, cyanobacteria were incorporated into viridiplantae, from which all green plants derive. I'm attaching a blowup of the phylogenetic tree from the same paper.

PlantEndo.gif

Now, how do we know this pathway? To an extent, we just got lucky. The Glaucophyta you can see in the diagram need not have survived; species have been going extinct for billions of years. Fortunately for biologists, they did survive, and the clear similarities to cyanobacteria in the glaucophyta plastid are evident, even in this picture.

Please do not read "absolute certainty" into my short declarative statements. Like all science, these results are tentative. I remove the cautionary modifiers only to make the material more readable.

Nor is this the only place where we've gotten lucky. From Inouye/Okamoto, "The concept of secondary endosymbiosis arose from early ultrastructural studies on cryptophyte and chlorarachniophyte algae (Greenwood 1974; Hibberd and Norris 1984). It is fortuitous that these two groups of algae have persisted for millions of years. Had they not existed today, secondary endosymbiotic theory would have taken much more time to be recognized and accepted."

We're not restricted to visual information here, as useful as that might be. Given recent technological advances in transcribing genetic information, we can compare organisms and organelles at the level of DNA. Plastids, like motichondria, have their own DNA, even if unlike mitochondria, that DNA has become incorporated to a very large extent into the nuclear DNA of the host organism. Plastid DNA is contained in the structure called the "nucleomorph."

From Inouye/Okamoto, "Molecular phylogenetic studies suggested that the nucleomorph of the cryptophytes is truly a vestigial nucleus phylogenetically related to the Rhodophyta, or red algae (Douglas et al. 1991), while that of chlorarachniophytes is related to the chlorophytes, or green algae (McFadden et al. 1994; Gilson and McFadden 1996; Van de Peer et al. 1996; Ishida et al. 1997)"

One thing bears mentioning here. In my experience, there are no creationist objections to evolution that have not already been answered by available research. This is almost startling. Given the ever-expanding realm of research, it should be expected that creationists would at least occasionally be able to seize upon an open question. Yet this never turns out to be the case.

What this says about the backwardness of creationism I leave to the reader.

As ever, Jesse

[seer]

All species keep evolving over time; that is the nature of the imperfect genetic copying process. But not all change their morphology.

- T

But you just said, Just because something can happen doesn't mean it must happen. So evolution does not necessarily happen - according to you.