What happened "before" evolution?

[Anaglyph]

@Polar_Iceman

Thanks for that; so to continue off on this tangent:

If the species can be identified by a “barcode” in the DNA, does this mean that the barcode segment defines the species, and that all life shares a certain proportion of DNA, except for the “barcode” segment?

Could I, hypothetically, extract and mix 'n match the barcode segments, attach them to a chunk of the common DNA, and still produce viable life forms, as defined by the “barcode” segment?

There is no “species barcode”. If you compare corresponding sequences of DNA across different species, you find that the more distantly related two species are, the more differences you find between the two sequences. If the number of differences in a given length of DNA is below a threshold within a large enough segment of DNA, you can deduce that the two sequences derive from two individuals of the same species.

Parts of the DNA that code for important proteins show a lower number of differences, because changes (mutations) that impair the functions are discarded by natural selection, while parts of DNA that have no specific function are highly variable. Therefore, if you want to determine the degree of relatedness between closely related individuals (e.g. paternity test), you look at these highly variable sequences, and if you want to determine the degree of relatedness for distantly related species, you look at genes that are known to allow only very little change.

[Leo_Bloom]

[QUOTE=Mijin]
…

Actually, look what other organs we have paired. Hands! Knees! Eyes! It’s almost like the default is for organs to be paired in a bilaterally symmetrical organism, unless they’re along the lateral line (in which case they’re often composed of two hemispheres).
[/QUOTE]

On the evolutionary history of bipolarity (a huge topic) the following quickie might be of some interest.

An inquirer writes: What’s so good about bilateral symmetry? Why is it so successful? I understand that 1. having a head to figure out where to move and 2. having forward going part and a backward following part both could lead to bilateral symmetry…but couldn’t they lead to other structures as well? Why two eyes and not three? Why not five legs? Is it that two-sided symmetry is easier to develop so a more foolproof way to get from fertilized egg to adult? Is it that the most successful ways of moving involve two motions (right/left for a fish, fall/jump for runners)? I’m perplexed.

Response at:

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[DrFidelius]

I hate bipolarity, it’s awesome!

[Voyager]

@Polar_Iceman

This response really lies at the root of my question. In all of my reading of late, it seems to me that the biological sciences are a mish mash of hard fact, speculation, dogmatism and leaps of faith.

As a case in point, your assertion that the prototype cell is the result of evolutionary processes seems to me to fall into the categories of dogmatism and faith, as opposed to demonstrable fact.

Why? A virus is not considered to be living, but it does reproduce and evolve. Why couldn’t a virus-like object exist an environment where it would pick up “food” from the environment, and where there were no more advanced organisms? We certainly can’t expect to find fossil records of such things.

I’ve seen some articles on membrane like substances which some of these things could have gone into, where they would be like a cell wall protecting them from the outside environment.

The life sustaining processes of even the simplest cell are of immense complexity; all of which are interconnected and interdependent. Many of these processes are well documented in the texts I have been reading, and I have no argument with that hard science.

And where to you get the idea that a cell was first? That is creationist nonsense, used I suppose to make evolution unlikely because of the complexity of modern cells - all of which have evolved for nearly a billion years.

However, my objections arise from the explanations as to how these processes came to be. The postulates that this level of complexity came to be by evolutionary processes really require an immense leap of faith, and fly in the face of even simple statistics.

Why do you think that?
Here is my favorite analogy about complexity. Say you have to open a lock which requires you to set 1,000 10 digit dials correctly. There are 10 ** 1000 combinations - so guessing it would be impossible, right? But I didn’t tell you something. Each dial, in order, clicks when you have the right digit. Now opening this impossible lock is easy. A mutation that allows a creature to reproduce more successfully is like that click, and no complex organism evolved in one step. My analogy is incorrect in one way - it assumes a goal, which is not the case in evolution - so it is even easier.

So while I appreciate and acknowledge that your responses are consistent with what I have been reading in current texts, I find that they really do lack in credibility.

Hence my question regarding a third alternative: without invoking “God” or highly improbable “evolutionary processes”, how could a fully functional living cell appear on the scene?

I trust I’ve answered this. As has been mentioned previously, the simple cells which first evolved would have been out-competed and would disappear, leaving only the more complex and sophisticated ones we see today.

[Leo_Bloom]

@DrFidelius

I hate bipolarity, it’s awesome!

I am bipolar (bipolar 1, mixed, since you asked).

It is awesome when you’re king of the world and think your checking account has $100,000 in it, and act accordingly. Or the other side of the median.

Then I hate it when I’m in the loony bin for three weeks.

[[sigh]]

[TriPolar]

@Leo_Bloom

I am bipolar (bipolar 1, mixed, since you asked).

It is awesome when you’re king of the world and think your checking account has $100,000 in it, and act accordingly. Or the other side of the median.

Then I hate it when I’m in the loony bin for three weeks.

[[sigh]]

I feel the need to one up you.

[Polar_Iceman]

The numerous responses to my question caused me to do some thinking and triggered one of those “Eureka” moments; I think I may have answered my own question.

Rather than me respond directly to the individual questions asked, let me respond with an analogy which I think addresses the major issues, at least as they are in my mind.

Consider NYC; this is a megalopolis of great complexity and for the purposes of illustration could be considered an analogue of a cell. Therefore, using a bit of poetic licence and made up history, the evolution of NYC could be considered analogous to that of living organisms.

A couple of hundred years ago, a handful of settlers landed on the shores of Manhattan Island and established a small colony. With the passage of time, the residents grew in number, and as their number grew, their requirements also grew. Individual settlers specialised: some became builders, some became accountants, some became street cleaners. Each of these specialities evolved in response to a particular need.

The individual specialties applied their expertise and constructed their required physical facilities, supporting infrastructure and whatever supply and distribution systems were required to both maintain and enhance their individual lives and the city.

Over an extended period of time, the current city evolved into its current complexity. Food and supplies flow in, are distributed as needed, and wastes are removed. Internally, structures and facilities are constructed, renovated or demolished as needed.

In a broader perspective, the world outside the city could be considered a supply and support source for the needs of the city. For example, the cornfields of Kansas could be considered to be the nutrients supply, and the oilfields of the Middle East could be viewed as an energy supply. With the tapping of these supply sources, and entire supporting transport and distribution system evolved.

In parallel with this, the technological sophistication of the population evolved and eventually they developed the Cray super computer, and all its operating systems and application software. This computer then came to embody all they needed to know about maintaining and perpetuating the city.

To summarise the analogy: the cell is the city, the body is the world, and the Cray is DNA.

To my thinking, this analogy does explain a lot of the questions I have about the whole evolutionary process. However, it does leave one question: what is the biological equivalent of the original colonial settlers?

[Voyager]

@Polar_Iceman

To summarise the analogy: the cell is the city, the body is the world, and the Cray is DNA.

Good up to here. Control through DNA is more distributed than your Cray analogy recognizes. It might be more like a library of manuals which are everywhere, and which all city workers consult how to do their jobs. The Cray might represent the brain and high level planning, which works because it is not involved in the details.
Your analogy correctly does not have anyone planning the development of the city over the centuries - it evolved in reaction to the challenges of the moment.

To my thinking, this analogy does explain a lot of the questions I have about the whole evolutionary process. However, it does leave one question: what is the biological equivalent of the original colonial settlers?

Perhaps the first self reproducing molecules? Think of a primitive molecule, assembled by chance, with the ability to reproduce by bonding with smaller molecules until a mirror image is created - like RNA/DNA, but much simpler. And think about if the reproduction were imperfect. Any change that would involve attracting molecules which were more common would lead to that “mutation” out-reproducing the original one and spreading. A mutation which allowed it to grab chunks of broken molecules ditto - maybe more primitive and shorter versions. That is like predation. I’m not saying that this is how it happened, but it seems like a plausible mechanism.

[Polar_Iceman]

@Voyager

Perhaps the first self reproducing molecules? Think of a primitive molecule, assembled by chance, with the ability to reproduce by bonding with smaller molecules until a mirror image is created - like RNA/DNA, but much simpler. And think about if the reproduction were imperfect. Any change that would involve attracting molecules which were more common would lead to that “mutation” out-reproducing the original one and spreading. A mutation which allowed it to grab chunks of broken molecules ditto - maybe more primitive and shorter versions. That is like predation. I’m not saying that this is how it happened, but it seems like a plausible mechanism.

Your response has got me thinking: assuming that the analogy holds, the chemical version of it should be testable and reproducible. Surely somebody has already thought of this and done the experiments?

If so, what would be the starting molecule, and what would be the sequence of subsequent molecular products?

[Exapno_Mapcase]

@Polar_Iceman

Your response has got me thinking: assuming that the analogy holds, the chemical version of it should be testable and reproducible. Surely somebody has already thought of this and done the experiments?

If so, what would be the starting molecule, and what would be the sequence of subsequent molecular products?

Short answer: nobody knows. It’s a difficult problem, since all we have are some of the later end-products, and the possible lines from simplex to complex are numerous.

Scientists consider a deep problem like this absolutely wonderful, the reason they got into the profession. What they would like outsiders to understand is that there are only two possible scientific states: knowing the answer and looking for the answer. Postulating magic as an alternative is guaranteed not to yield any answer at all.

[Polar_Iceman]

@Exapno_Mapcase

Postulating magic as an alternative is guaranteed not to yield any answer at all.

Postulating magic??? Did I miss something???

[si_blakely]

@Polar_Iceman

Your response has got me thinking: assuming that the analogy holds, the chemical version of it should be testable and reproducible. Surely somebody has already thought of this and done the experiments?

If so, what would be the starting molecule, and what would be the sequence of subsequent molecular products?

The problem is no-one knows the starting conditions - there are a number of candidates.

The original focus was the atmosphere/water phase - the Miller/Urey experiment. While it produced a number of amino acids, the experiments have not really progressed beyond that.

The discovery of Black Smokers produced a new avenue for research - these geothermal vents have gradients of heat, chemicals and pressure, and the precipitates form complex environments that could trap active chemicals in cell like structures. The bacteria that populate/utilise these environments are primitive and utilise a variety of chemical energy sources that are not common on the planets surface - they provide some clues.

There have been experiments with some demonstrations of interesting results, but nothing conclusive - researchers are restricted by volume, time and funding where nature had billions of years and an entire planet surface to carry out experiments. Researchers are more directed, but may also be blinkered - suffice to say, they are not there yet.

Si

[Punoqllads]

@Polar_Iceman

Postulating magic??? Did I miss something???

Postulating magic = Awizarddidit. E.g., before there was life, the Invisible Pink Unicorn (If she’s invisible, how do you know she’s pink? Faith!) dipped her horn into the primordial mud, and then: life!

[Smeghead]

@Polar_Iceman

Your response has got me thinking: assuming that the analogy holds, the chemical version of it should be testable and reproducible. Surely somebody has already thought of this and done the experiments?

If so, what would be the starting molecule, and what would be the sequence of subsequent molecular products?

There have, and continue to be, a huge number of experiments attempting to recreate the earliest chemical reactions that could lead to life, with varying levels of success. It’s a tough problem, though, for a few reasons. First, there are a HUGE number of possible starting conditions, and any component could turn out to be absolutely vital. Second, some of these starting points are difficult to reproduce on earth. Finally, the original mixture had millions of years to progress from chemical to life. We’re trying to reproduce that process in terms of, at most, a few years.