Difficulty understanding evolution

[DiracPool]

but I am always concerned it won't talk about the inbetweens that I worry about.

I'm going to cop stevendaryl's plea here and say that I haven't been following the thread even though I was the "first responder." That said, the issue of the "in-between" species or forms is a legitimate concern and the point to be made here is that there are plenty of intermediate forms that are found to be statistically significant. Those stats are low, though, because intermediate forms are an extreme rarity. Why? Because speciation and the genomes that embody them are like trajectories in chaotic attractors. A species is like a limit cycle attractor. It kind of goes round and round in it's own little niche until it is forced out of that niche for one reason or another. Then it (or more accurately the population) undergoes a bifurcation event where you separate the wheat from the chaff. You can call this the transitional or "intermediary" period, as you referred to it. What is the transition? You name it, maybe it's fins to arms, or to wings. Why don't we have transitional forms? Well we do. The problem is that fossilization of forms is an extremely rare event. So, to find evidence of a fossilization of a transitional form is something along the odds of multiplying a derivative by a derivative (or squaring a derivative), in which case we usually just regard it as a negligible value. Even so, we do do find intermediate forms, surprisingly enough. However, they are very rare for the reasons I described.

So the issue shouldn't be, "why don't we find more intermediate forms." the issue should be, "Wow, I can't believe we've found so many intermediate forms."

Another good metaphor to think about when you think about evolution is something else. Think about a bunch of salad bowls. Maybe 64 of them in an 8x8 array. Now think of a marble bouncing around in one of those bowls. Don't move the array. The marble stays in one bowl. Now shake the array slightly. The marble bounces around but still stays in one bowl. Now shake it some more. At some point the exaggerated shaking is going to bounce the marble out of that bowl and into another another bowl. This is a chaotic dynamics description of speciation. Once the marble transitions into the other bowl, or well, we have a speciation event.

But, the important point is that the marble, or more accurately. marbles (plural) can stay in that bowl indefinitley, for years or thousands or millions of years. It takes some kind of dramatic event to shake it up to the point where you can shake the marble from one bowl to the other. But it does happen and that is what we call a speciation event. But, again, as the analogy suggests, it is a very rapid conversion, akin (in geological timescale) to a ball rolling around in a bowl and then suddenly gaining enough energy to leave that bowl and fall into a different bowl. That is the transitionary period and it is very short. So, it's not wonder why there isn't a huge representation of these transitional forms in the fossil record.

 

[gmax137]

Sorry, I hope this isn't de-railing the thread (maybe this question should be the start of a new thread?) I'm going way back to Post #50, where eltodesukane said:

---
The regular use of Caesarean sections is having an impact on human evolution, say scientists.
More mothers now need surgery to deliver a baby due to their narrow pelvis size, according to a study.
Researchers estimate cases where the baby cannot fit down the birth canal have increased from 30 in 1,000 in the 1960s to 36 in 1,000 births today.
Historically, these genes would not have been passed from mother to child as both would have died in labour.
Researchers in Austria say the trend is likely to continue
"Without modern medical intervention such problems often were lethal and this is, from an evolutionary perspective, selection.
"Women with a very narrow pelvis would not have survived birth 100 years ago. They do now and pass on their genes encoding for a narrow pelvis to their daughters."
http://www.bbc.com/news/science-environment-38210837

Where are these narrow-pelvised women coming from, if the millions of years / generations have been selecting for wide pelvises? Is there a steady stream of mutation to unusually narrow pelvises? When we were talking about eye-spots it was noted that the individuals lacking the spots were eaten before reproducing, hence the population becomes spotted. Why hasn't the human population become entirely wide-pelvised?

 

[peety]

I suppose that as medical intervention and surgical technology improves we move towards survival of the less fit but more desired by the more affluent. Just as we have bulldogs with breathing problems we'll have more people with weak hearts and other survival disadvantages.

 

[Ryan_m_b]

No, human women aren't being significantly affected by ceasarians. PZ Myers (prominent blogger and biologist) went over the paper here:
http://freethoughtblogs.com/pharyng...-havent-been-shown-to-change-human-evolution/

 

[Kaura]

Natural selection is a self correcting system more or less
When dealing with large population traits that give even a slightly better chance of survival and reproduction typically emerge
This is why certain things such as random seemingly inconsequential deformities are not often to be passed down on a large scale

 

[grumpup]

One word - Darwin.

i.e. survival of the fittest, but remember the survival takes place in time. What is best at one point in time is not necessarily best at all points in time.

You said "I am and athiest and I believe on [sic?] evolution."

The Greeks thought faith to be assent by the intellect w/o evidence. What is there to believe about evolution that is not evidenced by nature? And I do mean evidenced not proved. Because nothing asserted by science can be "proved", only supported by evidence.

A few years back where I live there was a kerfuffle about stickers in science textbooks. A physics teacher was quoted in the newspaper that "I believe in science." I hold that was sufficient evidence to immediately either terminate his employment or send him for remedial education. He understood neither science nor faith.

 

[houlahound]

Good point, i don't believe in science. I accept the evidence.

 

[Drakkith]

Good point, i don't believe in science. I accept the evidence.

Remember that language is fairly flexible, and even if you're not using a word correctly, the overall idea you're trying to convey is usually intact.

That being said, the phrase "I believe in science" is perfectly valid. See the definitions of "believe" here: http://www.dictionary.com/browse/believe?s=t

 

[houlahound]

I don't believe the world exists. I don't believe the internet exists... said while posting to it.

That's how I use the word "believe". Yes it seems problematic as a general word.

 

[zinq]

"But surely some mutations that wernt asthetically pleasing or slightly non uniform wernt always a problem for survival."

They may not seem to have been a problem for survival. But besides the basic aspects of survival like getting air, water, and food, there is also the issue of whether one's genes will survive to the next generation. For better or worse, symmetry is extremely important with (at least) humans' mate selection. Many other animals also have very stringent standards for mate selection.

I don't want to pretend that evolution is a simple, obvious thing to me; it certainly is not. I'm usually not surprised about the traits that are bred *out* by natural selection. What amazes me is that there are enough *positive* mutations to create astonishingly specific and complicated structures (including mental ones) like Beethoven's ability to compose ineffably beautiful classical music — or even a parrot's brilliant flash of spectral colors.

But I chalk up my amazement at these things to simply not having an intuition that is equal to the task of imagining what is possible to occur in billions of years.

 

[houlahound]

I have seen wild boar mutate after 10 years of drought.

I have seen pet cats mutate into an unrecognisable feral species with colours you will not find in the domestic world.

The structure of skeletons, teeth, colour, scent... I have personally observed them mutate in my own life time.

 

[Drakkith]

I have seen wild boar mutate after 10 years of drought.

I have seen pet cats mutate into an unrecognisable feral species with colours you will not find in the domestic world.

The structure of skeletons, teeth, colour, scent... I have personally observed them mutate in my own life time.

Most of these are unlikely to be the result of mutations. They are probably the result of genetic recombination and gene expression.

 

[houlahound]

Agouti, sable, black brindle cats - where have you seen that in domestic cats??

All our wild cats here are from domestic stock.

 

[Adamchiv]

Just to let everyone know I fully understand the difference between blind assertion and imperical evidence, and that science doesn't really deal in facts, only theories that advance and become a body of evidence. Can I point out I mentioned atheism because I knew some of my questions would seem very phyloslophical and I didnt want to leave the impression that I was a creationist trolling this forum.

For the admin, I know this is becoming unscientific, and hope we can get back on topic asap

Can anyone tell me at roughly what point all the main organs became inherant, I know its gradual, but for example did our ancestors (i.e earliest life forms) live a long time without a liver, or kidney etc

 

[houlahound]

this is a physics community granted on a biology sub- forum. Have you considered joining a biology forum with a dedicated evolutionary biologist community.

No offense to the physicists here.

 

[Bystander]

For the admin, I know this is becoming unscientific, and hope we can get back on topic asap

Hear. Hear.

 

[Adamchiv]

this is a physics community granted on a biology sub- forum. Have you considered joining a biology forum with a dedicated evolutionary biologist community.

No offense to the physicists here.

No because the answers here have been very helpful

 

[Drakkith]

Agouti, sable, black brindle cats - where have you seen that in domestic cats??

All our wild cats here are from domestic stock.

I'm pretty sure I found all of those on domestic cats in google images just now. But I don't know cat coat colors that well, so I may be mistaken (though I did look them up to try to make sure).

Can anyone tell me at roughly what point all the main organs became inherant, I know its gradual, but for example did our ancestors (i.e earliest life forms) live a long time without a liver, or kidney etc

Basic organs were part of the earliest multicellular life forms. As an example, take a look at a jellyfish. They've been around for somewhere between 500 and 700 million years and they have multiple rudimentary organs, including a nervous system, digestive system, and more. These organs aren't nearly as complex as ours, but they were probably among the most advanced organs at one point in time.

Organs that more closely resemble ours can be found in fish and evolved somewhere around 350-400 million years ago. The main organs are probably a hard requirement for complex life to develop. Without ways to efficiently process food, get rid of wastes, and seal the organism's internal systems from the outside world, complex life cannot develop.

 

[Adamchiv]

Without ways to efficiently process food, get rid of wastes, and seal the organism's internal systems from the outside world, complex life cannot develop.[/QUOTE]

Youve just sent me on another tangent why did we ever (again I say we as the whole spectrum of evolved life) start to need oxygen and require food? Does this stem back to the fact that bacteria requires some sort of energy nurishment? And does bacteria need oxygen? Does it all stem back to bacteria? Or a little further down the line? (Sorry) your previous answer was very helpful

 

[Bystander]

why did we ever (again I say we as the whole spectrum of evolved life) start to need oxygen and require food?

Energy. Are there other energetic chemistries than coupled oxidations and reductions? Yes. Are they common? No.

 

[BillTre]

Oxygen allows biochemical processes to extract more energy from their food molecules.

Life is pretty energy intensive (compared to a rock).
In some cases each proton moved across a membrane is pumped with cellular energy.
The addition of each amino acid to a protein chain uses energy.

 

[Drakkith]

Youve just sent me on another tangent why did we ever (again I say we as the whole spectrum of evolved life) start to need oxygen and require food? Does this stem back to the fact that bacteria requires some sort of energy nurishment? And does bacteria need oxygen? Does it all stem back to bacteria? Or a little further down the line? (Sorry) your previous answer was very helpful

All living things expend energy to stay alive, even bacteria and other unicellular organisms. The source of this energy is whatever the organism uses as food. Oxygen or other chemicals are required to complete the reaction, which generates other molecules like adenosine triphosphate (ATP) that serve as the immediate energy source for each cell. I believe ATP is used in all living creatures, so it likely evolved LOOOONG ago.

 

[rootone]

The first lifeforms on Earth did not need Oxygen, at least not as a free gas.
When some later life evolved photosynthesis using light as an energy source, they released free Oxygen as waste.
Only then did Oxygen became a major component of the atmosphere
This turned out to be deadly rather than nourishing for most of the previously existing organisms.
https://en.wikipedia.org/wiki/Great_Oxygenation_Event

These first photosynthesizing microbes are probably the common ancestor of all plant life on Earth today.

 

[sarrabeth]

It seems as though you've picked up too much information on evolution, without a proper framework to put it on. That often happens when you're teaching yourself through books or videos. For a basic understanding of evolution, I recommend Nova's Judgment Day. It will also tell you how a whale's nose ended up on the top of it's head, and ours didn't.
Mutations are random, but evolution moves in whatever direction the species needs to go in order to survive (hopefully). The variety of genes that exist in a population are what ensures survival. There's a moth, in England, that hides on the bark of a tree. The moth is a greyish white, with black speckles, as is the bark of this tree. At one time, 3 out of 4 moths were this color, with the odd one more of a black. The black ones were easily seen against the white bark, and few survived. In the 19th century, England was burning huge amounts of coal, and the bark of the trees began to turn black. Before long, 3 out of 4 moths were black, rather than white. When cleaner fuels were used, the trees began to look white again, and the moths went back to their original color. This is not evolution, it is an example of how natural selection works on the existing variations in the gene pool. Natural selection is whatever predator is eating the moths that don't blend in. If the black ones are eaten, than the white ones survive, and vice versa.

 

[Drakkith]

When cleaner fuels were used, the trees began to look white again, and the moths went back to their original color. This is not evolution, it is an example of how natural selection works on the existing variations in the gene pool.

No, that's evolution also. Evolution is simply the change in heritable traits in a population over time, and it includes the causes of that change.

 

[sarrabeth]

No, that's evolution also. Evolution is simply the change in heritable traits in a population over time, and it includes the causes of that change.

Thank you for responding.
It seems to me that the heritable traits have not changed, since both colors were and are present. If the situation had not changed, and continued to favor the darker colored moths, maybe the lighter variation may have disappeared, but I doubt it. The very fact that a population has a lot of variations is a way of ensuring that a portion of the group might survive a sudden change in environment. If the genome of a group is too similar, all it takes is a new disease or climate change to pretty much wipe it out. Or humans moving into the area.

 

[Drakkith]

It seems to me that the heritable traits have not changed, since both colors were and are present.

The traits themselves have not been altered, as this isn't an example of a mutation, but natural selection acted upon the population and changed the proportion of white vs dark colored moths in response to the changing environment. This is a clear-cut example of evolution. Note that natural selection is a mechanism by which evolution occurs, and it is only one of several mechanisms. Other mechanisms include genetic drift and genetic hitchhiking.

See here: https://en.wikipedia.org/wiki/Peppered_moth_evolution

The very fact that a population has a lot of variations is a way of ensuring that a portion of the group might survive a sudden change in environment. If the genome of a group is too similar, all it takes is a new disease or climate change to pretty much wipe it out.

Indeed. Variation is important to ensuring a population is resistant to sudden changes in their environment or exposure to diseases.

 

[lavinia]

I sent your question to a biologist friend. Here is the first part of his response.

"A lot of issues here. Let’s start with the lumps on the arms etc. First, one has to distinguish the evolution of complex structures from single gene mutations that occur in a single generation. The lumps on the arm are presumably an example of the latter. Whether any mutation is truly “neutral” meaning that it confers no selective advantage or disadvantage is still, I believe, a matter of debate. However, if mutation does not confer a selective advantage, it is likely to be diluted into the gene pool to such an extent that it’s reappearance seems more like a random event. There are mutations that fit this description - white forelock, sixth finger etc. Note that neutral or even deleterious mutations can gain in frequency in a subpopulation where inbreeding occurs and dilution is not possible. So, for example, the hemophilia mutation is relatively common on Pitcairn island as well as in the British royal bloodline. The bottom line here is that we don’t have lumps on our arms because the lumps confer no selective advantage and we are not inbred.

More on the complex structures in a subsequent note when more time is available. "

 

[Adamchiv]

I sent your question to a biologist friend. Here is the first part of his response.

"A lot of issues here. Let’s start with the lumps on the arms etc. First, one has to distinguish the evolution of complex structures from single gene mutations that occur in a single generation. The lumps on the arm are presumably an example of the latter. Whether any mutation is truly “neutral” meaning that it confers no selective advantage or disadvantage is still, I believe, a matter of debate. However, if mutation does not confer a selective advantage, it is likely to be diluted into the gene pool to such an extent that it’s reappearance seems more like a random event. There are mutations that fit this description - white forelock, sixth finger etc. Note that neutral or even deleterious mutations can gain in frequency in a subpopulation where inbreeding occurs and dilution is not possible. So, for example, the hemophilia mutation is relatively common on Pitcairn island as well as in the British royal bloodline. The bottom line here is that we don’t have lumps on our arms because the lumps confer no selective advantage and we are not inbred.

More on the complex structures in a subsequent note when more time is available. "

Thanks very much to you and your biologist friend! I will read up on the hemophilia mutation

 

[lavinia]

Here is the second installment of my friend's response.

"
Where complex structures like a nose and mouth are concerned, it must be appreciated that they did not arise as a single mutational event, but developed as stepwise elaborations of primordial structures. In multicellular invertebrates that are either sessile or that do not benefit from movement in a straight line (e.g. sea cucumber, slime mold) there is no selective advantage to development of a midline around which structures are placed symmetrically. However, in multicellular vertebrates for whom movement is a straight line is advantageous for targeting food sources, escaping predators, etc., development around a midline has a selective advantage. Symmetrical development around this midline helps maintain this selective advantage (fins on either side of the fish vertebral column, legs on either side of the early amphibians), and this arrangement thus dominates the anatomy of multicellular vertebrates. The nose is not a single structure but a complex one that connects both to the respiratory system and the brain. It is situated around the midline, with parts placed symmetrically on either side of the midline. The same holds for the mouth, which is just a part of the digestive system. While it’s theoretically possible to find a mouth at, say, the top of the forehead in the midline, evolution of the digestive system occurred in a coordinated fashion with the central nervous system. For the mouth to be at the very top of the head, the esophagus would then have to travel through the brain without disrupting brain function, which depends on communication between neurons on either side of the midline, and which was also evolving with the digestive system. Given the arrangement of these structures in primordial species, it is highly unlikely that any single genetic event could effect such a dramatic rearrangement. Moreover, were that to happen, it is prohibitively unlikely that the new arrangement would confer a selective advantage.

The notion that complex structures arise as stepwise changes in corresponding systems found in ancestral species also holds for networks like the circulatory system. Circulation arose to allow cells deep inside solid organs receive needed oxygen, and once the system developed, it is not feasible to imagine new organ systems arising that would obtain oxygen by some other method. Note that in insects, which are invertebrates whose evolutionary tree goes back to ancestral invertebrates that did not have a circulatory system, such a system does not exist, and cells receive oxygen through conduits that connect from the surface of the body. The insect system is not too different from that of the invertebrate sea cucumber. It’s not surprising that the insect system is not well adapted to vertebrate organisms with very large organs that may be billions of cells thick. So, the insect system is built on the tubule structure also found in the sea cucumber, while the arterial/venous system is descended from the oxygenation system of early vertebrates.

The underlying motive force for skepticism about complex structures evolving rather that being designed by an intelligence stems, in my view, from a lack of appreciation of the amount of time evolution has been taking place. Most people cannot really get a handle on a time frame of 40 million centuries, which is a reasonable estimate of the time since life first appeared. A lot of genetic experiments that failed can take place over that expanse of time. "