Difficulty understanding evolution

[Adamchiv]

"why is it that our arms don't have big lumps all over them or, our ribcage have random points sticking out of each one, or an extra toe poking out the side of our foot."
-- Some do! I worked in a hospital and I saw myself many abnormal newborns, most of which dying at once or soon after. This is natural selection at work.
The healty ones live on, the dying ones die. No one said it was a happy process.
---
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

Thats very interesting and once again another point that I forgot to think about, that is imperfection for sure

 

[haruspex]

there are other causes like sexual selection but let's stick with the basics for now.

But this is a significant part of the answer to the original question, which I take to be more along the lines of "why are there not more mutations of a fairly cosmetic nature?" I.e. how is natural selection so effective at weeding at even small imperfections?
Potential mates care about about genetic fitness. A lop-sided face can be a consequence of a childhood illness, so we have evolved to find such faces less attractive.

 

[Adamchiv]

But this is a significant part of the answer to the original question, which I take to be more along the lines of "why are there not more mutations of a fairly cosmetic nature?" I.e. how is natural selection so effective at weeding at even small imperfections?
Potential mates care about about genetic fitness. A lop-sided face can be a consequence of a childhood illness, so we have evolved to find such faces less attractive.

Yes that is very much to do with some of my problem I have understanding. That makes a lot of sense to me. Heres another issue, how do the male and female sexual organs develop side by side to work so well, same for the sperm and the egg. I kind of imagine it to go way back to bacteria or slightly after, but I really really don't understand how. Because they must develop and evolve separate from each other

 

[haruspex]

Yes that is very much to do with some of my problem I have understanding. That makes a lot of sense to me. Heres another issue, how do the male and female sexual organs develop side by side to work so well, same for the sperm and the egg. I kind of imagine it to go way back to bacteria or slightly after, but I really really don't understand how. Because they must develop and evolve separate from each other

It depends what you mean by working well together. Many aspects of this, in many species, are an arms race. The female side raises barriers so that only the fittest make it ( at the sperm level and higher), while the male side wages war with rivals, e.g. by leaving a plug in place or inflicting physical damage on the female.

 

[Bandersnatch]

Heres another issue, how do the male and female sexual organs develop side by side to work so well, same for the sperm and the egg. I kind of imagine it to go way back to bacteria or slightly after, but I really really don't understand how. Because they must develop and evolve separate from each other.

If you can find the time, read Matt Ridley's book: 'The Red Queen: Sex and the Evolution of Human Nature'.

 

[Adamchiv]

If you can find the time, read Matt Ridley's book: 'The Red Queen: Sex and the Evolution of Human Nature'.

Thats great I'll take a look at that, it really puzzles me but I know science will have the answer

 

[BillTre]

Heres another issue, how do the male and female sexual organs develop side by side to work so well, same for the sperm and the egg. I kind of imagine it to go way back to bacteria or slightly after, but I really really don't understand how. Because they must develop and evolve separate from each other

Yeast (a eukaryote and a fungi) and some bacteria have mating types, but they don't have sex organs. DNA exchange should only proceed between individuals with different mating types.
Although DNA is exchanged between these different mating types, they don't have sex organs or specialized reproductive cells like sperm, eggs, pollen, ovules (plant equivalent of eggs).

Sex organs are restricted to metazoan animals and plants have sex cells as a specialized sub-set of all the cells in their bodies.
Sex organs support the production of the gametes and are used for transferring gametes (sperm, pollen) so they can meet up with and fertilize eggs and ovules.

Some animals are both male and female (like most plants) at the same time. Some are first one sex than the other.
Again, selection has selected for them to work (either together or a lone) to achieve their function of reproduction (the most important biological property).

They don't always have to work together. Some worms will stab through the females skin with their "penis-like-thing" the get their sperm in the females body cavity where they will eventually find the eggs to fertilize. This requires little coordination with the females sex organs.
Some animals have sophisticated sperm storing organs that can keep sperm viable for months for fertilization long after copulation.

Just to add to the complexity, sex chromosomes can also evolve and change.

 

[Adamchiv]

Yeast (a eukaryote and a fungi) and some bacteria have mating types, but they don't have sex organs. DNA exchange should only proceed between individuals with different mating types.
Although DNA is exchanged between these different mating types, they don't have sex organs or specialized reproductive cells like sperm, eggs, pollen, ovules (plant equivalent of eggs).

Sex organs are restricted to metazoan animals and plants have sex cells as a specialized sub-set of all the cells in their bodies.
Sex organs support the production of the gametes and are used for transferring gametes (sperm, pollen) so they can meet up with and fertilize eggs and ovules.

Some animals are both male and female (like most plants) at the same time. Some are first one sex than the other.
Again, selection has selected for them to work (either together or a lone) to achieve their function of reproduction (the most important biological property).

They don't always have to work together. Some worms will stab through the females skin with their "penis-like-thing" the get their sperm in the females body cavity where they will eventually find the eggs to fertilize. This requires little coordination with the females sex organs.
Some animals have sophisticated sperm storing organs that can keep sperm viable for months for fertilization long after copulation.

Just to add to the complexity, sex chromosomes can also evolve and change.

Interesting, do you think that the human genitallia both male and female evolved independantly of each other for a long time? Was there a point when there was maybe one organism that reproduced and a split happened causing a male and female to evolve from it, one carrying the male components and the other the female components (in terms of reproductive cells) I don't mean suddenly there was man and woman like the biblical stories. I guess what I am trying to say is there must have been a point where male and female happened from when we evolved from bacteria up until we became two separate genders

 

[BillTre]

The two sexes had to evolve together in that they make haploid sex cells (sperm and eggs).
Haploid cells have only one copy of each chromosome. When the egg and sperm combine, they then have two copies of each chromosome (one from each parent), which makes them diploid, the normal state for animals. If they were haploid they would probably die before reproducing. If this were done without making the sex cells haploid, each generation would double its number of chromosomes, which would end badly.

Haploid cells are made by meiosis (special cell divisions that reduce the chromosomal number) rather than the more common mitosis (cell division without changing the chromosomal number). This requires males if there were females and visa versa. They have to had developed together.

 

[Drakkith]

Interesting, do you think that the human genitallia both male and female evolved independantly of each other for a long time? Was there a point when there was maybe one organism that reproduced and a split happened causing a male and female to evolve from it, one carrying the male components and the other the female components (in terms of reproductive cells) I don't mean suddenly there was man and woman like the biblical stories. I guess what I am trying to say is there must have been a point where male and female happened from when we evolved from bacteria up until we became two separate genders

This likely occurred very, very early on the history of life. Most likely when all life was still unicellular with perhaps some very simple multicellular organisms. By the time that the first fish species evolved, sexual reproduction had already been in place a long time.

 

[Vanadium 50]

By the time that the first fish species evolved, sexual reproduction had already been in place a long time.

True. A very long time. Around the time of the common ancestor of plants and animals, 1.2 billion years ago. Fish are only about 500 million years old.

 

[rootone]

Sexual reproduction must have initially been one of those lucky mutations.
Before that, and still now, there are many organisms which have their niche and are doing fine without it.
Once that exists though, evolution probably speeds up, more variables to play with.

 

[Drakkith]

Sexual reproduction must have initially been one of those lucky mutations.

Not just one of those lucky mutations, but a lot of "lucky" mutations acted upon by natural selection. That may seem like it's very unlikely to some, and it certainly is, but natural selection had several billion years to build up to that point. Trillions upon trillions upon trillions of fast-reproducing cells and a couple billion years over which to act is a lot of chances.

 

[Jon Richfield]

Not just one of those lucky mutations, but a lot of "lucky" mutations acted upon by natural selection. That may seem like it's very unlikely to some, and it certainly is, but natural selection had several billion years to build up to that point. Trillions upon trillions upon trillions of fast-reproducing cells and a couple billion years over which to act is a lot of chances.

To me that seems to under-emphasise the non-stochastic nature of evolution, "evolutionary opportunism" building upon the nature of what had gone before. (I don't like the use of the term "heuristic" in this connection, because to me that suggests something too teleological).

I suspect that sexual reproduction was a by-product or consequence of the nature of duplication of nucleic acid by chain sequence matching and of cell formation and division at the time when the first cellular life was evolving. I suspect furthermore that it was preceded by phases where cell materials were rather freely exchanged and the concept of "species" was not yet well-defined. (Not that IMO it is all that cleanly defined nowadays, but let that be for the moment!)

 

[Drakkith]

To me that seems to under-emphasise the non-stochastic nature of evolution, "evolutionary opportunism" building upon the nature of what had gone before. (I don't like the use of the term "heuristic" in this connection, because to me that suggests something too teleological).

I'm not sure what you mean by this. Can you elaborate?

I suspect that sexual reproduction was a by-product or consequence of the nature of duplication of nucleic acid by chain sequence matching and of cell formation and division at the time when the first cellular life was evolving.

Sexual reproduction is thought to have evolved around 1.2 billion years ago. Life is thought to have arisen well over 3 billion years ago. Cellular life was around long, long before sexual reproduction evolved.

 

[Jon Richfield]

I'm not sure what you mean by this. Can you elaborate?

"Stochastic" in this sense would suggest that just any mutation in any organism would be equally likely and equally evolutionarily significant, like starting over with a new toss of a hatful of type every time it doesn't come out reading like a page of Shakespeare.
"Heuristic" would be like tossing again mostly the letters that didn't match the page.
Evolution by natural selection is more like the latter, but not much like either, because it is not teleological; there IS NO page to match for a foreknown and desired, or notionally correct outcome. ANY outcome that serendipitously improves successful reproduction rates (ie increases "fitness") represents progress in the short term, though in the longer term it might be disastrous.
So for example, a more muscularly competitive male or one better endowed with an impressive fertilisation mechanism might be the result of advantageous to a male in a particular generation. (It might prove disastrous later, but that is a problem for the teleologist.) But the same mutations might prove useless a hundred million years earlier, when say, muscles or intromission were irrelevant to reproduction.

Does that help?

Sexual reproduction is thought to have evolved around 1.2 billion years ago. Life is thought to have arisen well over 3 billion years ago. Cellular life was around long, long before sexual reproduction evolved.

Good luck; never mind demonstrating that, good luck just stating it meaningfully -- ask yourself what form the original sexual reproduction might have taken!

What do you mean by sexual reproduction? Virile males and complaisant females with functionally conspicuous secondary sexual features to match each gender? Long before anything of the type emerged, before even distinct gametes had evolved in prokaryotes, let alone eukaryotes, the genetic functions of nucleic acid reading for gene expression had existed, and probably even before that, reproduction of nucleic acid chains by base-pair matching. (Think out the information theory of the process!) Even today the expression of genetic information in prokaryotes is not all that well distinguished from reproduction.

Now, what is the essence of sexual reproduction; not the variety and mechanism of genders: it is a variable set of aspects of:

1. Given an organism that has an adequate genome, (typically in the form of paired NA chains, so I'll ignore any other form here, though that is not necessarily the only possibility) the organism can split the paired chains apart for reading, either for expression or duplication. In its simplest form this is "asexual" reproduction, such as in somatic cells or monocellular organisms.
2. An elaboration or in fact possibly a degeneration of that very mechanism could match the paired chains in the organisation of the first approach to chromosomes in the modern sense. This could have been very helpful in permitting primitive, asexual, forms of chromosomal reproduction; cells could thenceforth "tell" whether their own or daughter chromosome complements were complete, in contrast to some viruses such as flu.
3. A separated, but coordinated mechanism would be necessary for cell division, or we simply would wind up with a mass of undifferentiated cytoplasm stuffed with chromosomes or perhaps ancestral forms of chromosomes.
4. Inverse forms of division of cells and matching of chromosomes would lead to the merging of cells and matching of their genetic material. this would amount to a primitive form of fertilisation. Note that a key aspect of this form of combination would amount to the formation of a diploid zygote from two haploid cells or gametes.
5. To correct this condition that otherwise must lead to runaway polyploidy; we need a form of division that would halve the diploid chromosome complement to reinstate the haploid state, and precisely that is what meiosis means: reduction (commonly called reduction division).
6. That is what sexual reproduction amounts to. All the rest, genders, manes on lions, penes in males, special forms of gametes (anisogamy instead of isogamy) are frills; frills arising repeatedly in innumerable forms in response to selective pressures. It is the frills that began to become arguably detectable about 1 - 2 GY BP. Sexual reproduction was something like twice as old at a guess; maybe more.

I have a nasty feeling that I have forgotten a couple of books' worth, but it is a big subject, the realities are speculative, and I suspect that you time is not much less at a premium than mine, so if I have omitted anything disastrously, please let me know.

 

[Ryan_m_b]

General mod note: there's been a lack of references for a while, that was ok when we were covering the very basics but if the thread is trending towards the evolution of specific traits PF rules on citations become more important.

 

[Adamchiv]

General mod note: there's been a lack of references for a while, that was ok when we were covering the very basics but if the thread is trending towards the evolution of specific traits PF rules on citations become more important.

I think that we are dealing with each issue as it comes, this specific issue has become deeper but I think we are on the cusp of resolving it and moving into another sub topic. As the original poster I feel that this is leading very nicely through each specific query. Though I am certainly not the authority on here this is just my opinion

 

[BillTre]

Sexual reproduction is usually considered to have the following cycle whenever reproduction occurs:
1) diploid cells (having two sets of chromosomes) divide to reduce the number of chromosomes to half (haploid)
2) the fusion of two complementary haploid cells to restore the resulting fused cell to the diploid state

Functionally important for this are:
-eukarote chromosomes (linear chromosomes with teleomeres), https://en.wikipedia.org/wiki/Centriole
-pairing of homologous chromosomes to facilitate crossing over,
-cell division mechanisms that ensure the right chromosomes go to the right cell during division
The cell division mechanisms involve centrioles (spindle organizers), a spindle containing microtubules on which the chromosomes move during division and that is involved in cell division, and centromeres on chromosomes that attach them to the spindle so they can be moved to one of the daughter cells.
This is suite of features is found in almost all sexually reproducing organisms, except that some plants and fungi can do without the centrioles.

This is distinguished from the situation in many bacteria, where they have a circular chromosome (which is structurally simpler) and most reproduction involves duplicating the chromosome followed by cell division such that each daughter cell gets a chromosome.
Bacteria can exchange DNA and increase their genetic variability by mechanisms like conjugation, but this is not something that happens every time the organism reproduces and it does not mix whole genomes. It is thus an occasional mixing event compared to sexual reproduction.

Genes genetically linked together on a parental chromosome have the opportunity to break their linkage to neighboring genes and acquire new neighbors. This results in greater diversity in the genetics of the offspring because an important aspect of diversity is in the diversity of different gene combinations.

Most sexual organisms use sexual reproduction whenever they reproduce, however, some cases (such as hydras) can bud off of new organisms in a non-sexual way.
This results in a clonal derivative of the organism's somatic cells. No genetic differences from the parents.
Asexual reproduction can be a faster way to reproduce in a very permissive environment where the organism is thriving, not stressed and apparently doesn't need a genetic recombination to create potentially more adaptive genetic combinations. Asexual reproducers can often also reproduce sexually, in less optimal conditions, so that their offspring are produced with the possible genetic benefits of genetic recombination. Aphids can do this kind of thing.
Some animals have lost sexual reproduction completely (such as Bdellid rotifers and some fish and reptiles).

In animals, the haploid cells are the reproductive cells and the diploid cells are the somatic cells (most of the other cells in the body). In some fungi and plants the relationship is reversed (adults haploid, reproductive cells diploid), but because the above cycle is still used, its still sexual reproduction and results in a greater diversity of gene combinations.

As stated above:

Sexual reproduction is thought to have evolved around 1.2 billion years ago. Life is thought to have arisen well over 3 billion years ago. Cellular life was around long, long before sexual reproduction evolved.

this complex suite of features required for sexual reproduction probably arose in a common ancestor of plants, animals, fungi and protists (single celled eukaryotes). Eukaryotes have linear chromosomes, and a cell division mechanism to deal with them properly.

The original post was about sexual organs, not sexual reproduction, but an understanding of sexual reproduction underlies it.
Sexual organs are there because of the occurrence of sexual reproduction. Sexual organs support the production and survival of the specialized sex cells (internal sexual organs). Sexual organs (external gentalia mostly) are involved in delivering the male haploid genome (sperm in animals) to the female's reproductive cells (eggs in animals) for fertilization. These organs probably evolved later as reproductive mechanisms became more complicated and sex cells in metazoans become more specialized. Early fish-like-things (and some fish today) for example, just released gametes into the ocean where they largely rely on chance to find and combine complementary gametes. The delivery system is minimal, but the cells still reside in testes and ovaries.

 

[Adamchiv]

There is certainly enough detail in these previous posts to form a detailed understanding, I thank you all for such in depth analysis, it will take me a while but I think I can find some foundation there for sure. Could we discuss (and this may sound crude or silly) the mental stimulation involved in evolutionary reproduction, for example, I can't think of which animal it is but there are animals that are dying out because they don't want to mate. So first question is why do they lose their libido, second question is regarding stimulation, to get to a positive stimulation in reproduction is that trial and error? For example those that got a positive stimulation were more likely to reproduce? Because it doesn't exactly feel horrible does it and there are obviously very positive urges that can't have just "been" it must have been an evolutionary trait right? Hate to get into these crude things but again its part of the whole development of life without any conscious design that I would really like to understand

 

[rootone]

Have you heard of Occam's razor?
It's rule of thumb which says the simplest idea is most likely to be right.
https://en.wikipedia.org/wiki/Occam's_razor
When you start introducing intention of some 'thing' to make the Universe and life what it is,
then you have a whole load of explaining to do as to how that 'thing' got to exist in the first place.
.

 

[Drakkith]

So first question is why do they lose their libido, second question is regarding stimulation, to get to a positive stimulation in reproduction is that trial and error? For example those that got a positive stimulation were more likely to reproduce?

For organisms that don't want to mate, the catchall reason would be because of "stress". That stress can be because of shortages of food and water, population pressure, disease, captivity, and countless other reasons.

Because it doesn't exactly feel horrible does it

For some species, mating is extraordinarily painful, stressful, or even fatal. For example, male bed bugs stab the female through the exoskeleton and release their sperm into the female's body, where it is transported through the hemolymph to the ovaries. In some species (such as some mantises), the male is sometimes eaten after mating.

and there are obviously very positive urges that can't have just "been" it must have been an evolutionary trait right?

Yes, but narrowing it down to some specific reason that the trait was selected for is usually very difficult. What may seem like a huge negative, like being eaten after mating, can actually be beneficial to the survival of the organism's genes (a well-fed mate is more likely to survive and pass on your genes than a hungry one).

 

[eltodesukane]

An interesting reference (a bit off topic):
About domesticating foxes by human/natural selection (like wolves were domesticated to become dogs over thousands of years)
"In the 1950s a Soviet geneticist began an experiment in guided evolution. He wanted to show how domestication works"
http://www.bbc.com/earth/story/20160912-a-soviet-scientist-created-the-only-tame-foxes-in-the-world

 

[Adamchiv]

An interesting reference (a bit off topic):
About domesticating foxes by human/natural selection (like wolves were domesticated to become dogs over thousands of years)
"In the 1950s a Soviet geneticist began an experiment in guided evolution. He wanted to show how domestication works"
http://www.bbc.com/earth/story/20160912-a-soviet-scientist-created-the-only-tame-foxes-in-the-world

Thats on topic for me, because I think that domestication over time is further proof of evolution. I wonder how information is preserved and passed down from generation to generation. On a basic level, instinct. I suppose its proof that the brain is a physical organism that works within itself and the soul is a stupid concept. Because everything within us is physical in some form, surely on a quantum level the instinct passed down from generation to generation must be observable in some sense, it must be detectable as some sort of neurological bar code or something

 

[Drakkith]

Instinct doesn't work on the quantum scale. It is the result of the particular way systems of neurological cells are connected to each other in an organism.

 

[BillTre]

Domestication is a very interesting subject. A lot is known about it.

The information determining the instinctive behaviors is genetically encoded within the animal's genome.
This is information in the order of the base pairs in the DNA double helix, as interpreted by the cellular environment in which it resides. Its not a quantum level thing.

That Genetic Information would then direct the development of the nervous system to make those neural connections mentioned by @Drakkith. This is a complex process working through a variety of encoded developmental processes.
Environmental Information: Some of the development would be influenced by general environmental sensory input (for instance to refine the visual map), but that would be refining the genetically determined developmental processes that set-up these refinements.
Culturally Inherited Information (among the domesticated) does not seem to be important since domesticated animals (or plants) don't have to be raised in groups to express their domesticated traits.

 

[Adamchiv]

Domestication is a very interesting subject. A lot is known about it.

The information determining the instinctive behaviors is genetically encoded within the animal's genome.
This is information in the order of the base pairs in the DNA double helix, as interpreted by the cellular environment in which it resides. Its not a quantum level thing.

That Genetic Information would then direct the development of the nervous system to make those neural connections mentioned by @Drakkith. This is a complex process working through a variety of encoded developmental processes.
Environmental Information: Some of the development would be influenced by general environmental sensory input (for instance to refine the visual map), but that would be refining the genetically determined developmental processes that set-up these refinements.
Culturally Inherited Information (among the domesticated) does not seem to be important since domesticated animals (or plants) don't have to be raised in groups to express their domesticated traits.

But if you take an individual memory, its a very complex image or mental video, surely it must be stored in the mind as a type of data? Its in there and can be accessed, its unique too, so as a stored unique thought, surely it must have some sort of a pattern or code etc

*maybe this is for another thread

 

[Adamchiv]

Its ok I've just looked into how memories are stored and I don't think I need to discuss it on this thread and also its going to get off topic.

Can we continue about domestication being passed down, because it is interesting

 

[BillTre]

Instinct is a kind of behavior.
It doesn't have in involve memory.
Most instincts (in lower animals) can be thought of as actions, perhaps in response to a sensory input, in a particular environment.
This can just be built into a nervous system when it develops.

Not all domestication traits are behavioral.
http://www.maizegenetics.net/genetics-of-domestication in corn deal with things like number of seeds, attachment to stem, etc.

 

[Adamchiv]

Instinct is a kind of behavior.
It doesn't have in involve memory.
Most instincts (in lower animals) can be thought of as actions, perhaps in response to a sensory input, in a particular environment.
This can just be built into a nervous system when it develops.

Not all domestication traits are behavioral.
http://www.maizegenetics.net/genetics-of-domestication in corn deal with things like number of seeds, attachment to stem, etc.

But the baby kangaroo climbs up into the pouch when its born, this is literally its first moments. There must be some instinct passed on, it can't be tought

 

[Drakkith]

But the baby kangaroo climbs up into the pouch when its born, this is literally its first moments. There must be some instinct passed on, it can't be tought

That's right. Instinct is stored and passed on in the genetic information of the organism. It is, by definition, complex behavior that doesn't have to be learned. Note that instinct isn't "hard coded" into the genome. There is no gene in sea turtles that says, "Okay, when you're done hatching and you see water, run towards it as fast as you can!" Instead, genes contain information having more to do with protein structure, timing of molecular signals, and regulatory sequences (e.g. promoters, enhancers, and silencers that affect the rate of transcription of that particular gene). The combination of many different genes governs the overall development of the organism and this initial development sets up the neurological and chemical "circuitry" that governs how the organism's instincts function.

Can we continue about domestication being passed down, because it is interesting

Domestication itself isn't something that's passed down. To quote wikipedia, "Domestication is a sustained multi-generational relationship in which one group of organisms assumes a significant degree of influence over the reproduction and care of another group to secure a more predictable supply of resources from that second group."

However, the traits that we usually select for when domesticating animals or plants are indeed passed on to subsequent generations in exactly the same ways that any other trait is passed down. The only difference is that we are doing the selection instead of nature. If you haven't already, take a look at the following article: https://en.wikipedia.org/wiki/Selective_breeding

 

[BillTre]

But the baby kangaroo climbs up into the pouch when its born, this is literally its first moments. There must be some instinct passed on, it can't be tought

Yes it is passed on, genetically.

 

[houlahound]

The silver fox experiment showed interesting traits re domestication. In the op you mentioned atheism and evolution, they are unrelated concepts. Why did you mention them together?

Not all mammals find their way to suckle, puppies that don't die within 24 hours unless hand fed.

I train working dogs, the traits that make them work contradict domestication. Its a balancing act of selective breeding to push traits back or bring them forward. The whole thing is fluid, there is no steady state.

 

[Drakkith]

In the op you mentioned atheism and evolution, they are unrelated concepts. Why did you mention them together?

Just a note for everyone: Let's stick to the topic of evolution, please. I've already had to remove one post that veered off into religious matters. Further off-topic posts may result in a locked thread. I hate to remove posts for this reason, but they're off topic and experience has shown that people tend to get very, very heated when it comes to religious matters, and discussions tend to fly out of control very quickly.

 

[BillTre]

I train working dogs, the traits that make them work contradict domestication.

What is this contradiction you speak of?
Is it a general affect or something specific to the task they are being trained for?

 

[houlahound]

It's a lot of splaining, in a nutshell a dog's survival instincts a what we can exploit for work, too much and the dog is unworkable, too little and the dog is a useless lawn ornament.

Modern society selects for the dull, useless lawn ornament with no sense of survival. Interestingly the demand for working dogs in the agencies is sky rocketing but the pool is almost empty.

Did you see the Whitehouse dogs fail? That right there shows the contradiction in full. Those dogs had no defense drive, no dominance, and failed because of it.

The harder dogs would not have got the job to start with being too offensive but were what was required in that instant.

My current idiot dog would have had to been choked off the guy and would have gone after the handler because he would have perceived the handler was challenging him, too much the other... see the contradiction?

Conversely when the balance is right you get the dog that got Osama with SEAL team 6. Those dogs are rarer than hen's teeth.

 

[stevendaryl]

I confess to not having read this entire thread, so I'm not sure if I'm saying something redundant, but the original poster is making a false assumption about the way that genetics controls the physical form of a creature. (I think the jargon is: how genotype influences phenotype). Random mutations do not lead (usually) to random bumps and appendages. Genes don't specify precisely what goes where on your body. Instead, their control over your body is very indirect--they (mostly? completely?) specify the presence or absence of certain proteins produced by your cells. The impact of these proteins is very indirect. Much of the development of a vertebrate should be thought of in the following way:

• There is a basic plan for a vertebrate: A spine, a head containing a brain, two eyes, and a mouth at one end of that spine, approximate bilateral symmetry, a heart, blood vessels, a stomach, etc.
• Genes mostly just tweak this basic plan. They enlarge some parts, shrink other parts, fuse parts, split one part into two, etc.

So you're not likely to have a mutation to a vertebrate that would make a second head at its knee, or have a third arm growing out of the back of its neck. If a genetic mutation is too extreme, by far, the most likely outcome would be that the creature would fail to live long enough to be born.

 

[Ryan_m_b]

I confess to not having read this entire thread, so I'm not sure if I'm saying something redundant, but the original poster is making a false assumption about the way that genetics controls the physical form of a creature. (I think the jargon is: how genotype influences phenotype). Random mutations do not lead (usually) to random bumps and appendages. Genes don't specify precisely what goes where on your body. Instead, their control over your body is very indirect--they (mostly? completely?) specify the presence or absence of certain proteins produced by your cells. The impact of these proteins is very indirect. Much of the development of a vertebrate should be thought of in the following way:

• There is a basic plan for a vertebrate: A spine, a head containing a brain, two eyes, and a mouth at one end of that spine, approximate bilateral symmetry, a heart, blood vessels, a stomach, etc.
• Genes mostly just tweak this basic plan. They enlarge some parts, shrink other parts, fuse parts, split one part into two, etc.

So you're not likely to have a mutation to a vertebrate that would make a second head at its knee, or have a third arm growing out of the back of its neck. If a genetic mutation is too extreme, by far, the most likely outcome would be that the creature would fail to live long enough to be born.

All generally correct, though mutations can occur that lead to gross physical changes (such as hox gene mutations, though I'm unsure how drastic they were in the wild vs the lab) they tend not to. One of the sticking points the OP had was difficulty keeping in mind that mutations tend to be very minor and evolution happens across long time scales. Anecdotally I've found this a very common confusion amongst non-biologists.

 

[stevendaryl]

All generally correct, though mutations can occur that lead to gross physical changes (such as hox gene mutations, though I'm unsure how drastic they were in the wild vs the lab) they tend not to. One of the sticking points the OP had was difficulty keeping in mind that mutations tend to be very minor and evolution happens across long time scales. Anecdotally I've found this a very common confusion amongst non-biologists.

Certainly, a mutation can result in huge changes, but it's a mistake to assume that there are genes that literally specify every aspect of an organism's body. There isn't a gene for "how many heads do you have", and a gene for "how long is your left pinky" and a gene for "what is the distance between your eyes" and separate genes for the locations of every hair on your head. Instead, a single gene (or sequence of DNA) typically modifies many different aspects of the organism.

 

[Ryan_m_b]

Yup, I am aware of that.

 

[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.