Intelligence of Evolution

[Thefourth]

Has anyone ever been able to describe how evolution seems to know of the surroundings of an animal? For example how is it animals whose natural fur color matches that of their surroundings? Or how did the eye come about? How would it know to make an organ that picks up light waves and how to even translate the information?

[ewmon]

Here's a well-known example — Peppered moth evolution

 

This is true for all traits (not just coloration), and includes the senses (such as touch, smell, and sight), motor control (muscles, bones, tendons, and ligaments), intelligence (comprehension, abstract thinking, memory, etc), etc.

[TonyMcC]

It's down to what is known as "survival of the fittest". Fittest in this sense means what fits the environment best - not fittest meaning most healthy or strongest. If a mutation gives an advantage for an organism within its environment it has a better chance of survival and reproduction thus passing on the mutation to some of its ofspring. The mutation can be small and yet give a real advantage. A sucesson of mutations can, given enough time, produce something as complicated as the eye. All stages of eye devopment can be seen in some sea creatures. The most basic being light sensitive tissue that just warns of movement. In the land of the blind the one eyed man is king!

[D H]

Fittest in this sense means what fits the environment best - not fittest meaning most healthy or strongest.

It's not even that. Fittest is whatever maximizes the number of offspring that live to a breeding age and in turn have more offspring. Evolution is stupid, stupid, stupid. The fitness metric is local in time and in place. Evolution has no foresight, no global vision. The selection process can be particularly stupid when mate selection is the driver. Sex-driven evolution can result in some bizarre characteristics that otherwise would almost certainly have to be deemed "unfit".

 

Evolution is a slow and inefficient process with zero intelligence. Fortunately (for us), evolution has had about 4 billion years in which to conduct its slow and inefficient experiments.

Edited October 19, 2010 by D H

[TonyMcC]

D H - Don't disagree - Birds of Paradise are an example of what you say. But where there are predators survival depends on being able to evade them until offspring can be produced. If a mutation aids that then an advantage is gained. Obviously where life is "easy" being more able to attract a mate becomes an advantage. Evolution is really a "trial and error" situation with, I think, many more failures than sucesses. It certainly is inefficient without planned intelligence of any kind. I do believe Darwin used the word "fittest" in the way I describe?

Edited October 19, 2010 by TonyMcC

[D H]

In a sense, who cares what Darwin said? Darwin was the start, not the pinnacle, of modern biology. As a starter, his 19th century theory had no underlying mechanism. Using Darwin as a basis is kind of like analyzing atoms using the Rutherford model. We've progressed beyond that in the last hundred in physics; biology has had even more time to progress beyond Darwin's ideas. Biology has undergone at least two, maybe three major revolutions since Darwin's time, first with the modern synthesis in the 1930s and then again with molecular biology in the 1950s, maybe again in the 1970s when modern geology and biology started getting rid of gradualism as the sole descriptor for change.

Edited October 19, 2010 by D H

[TonyMcC]

D H - I can't work out whether we are agreeing with each other or arguing some point. I guess you are letting me know that as well as gradualism, evolution can be caused by other means such as punctuated equilibrium. Since both seem probable and since it applies to both scenarios (and any other that I can imagine) it seems to me that explaining the phrase "survival of the fittest" is relevant. If it is relevant then giving credit to the man generally believed to have expressed it seems fair even if at that early stage he did not have the whole picture.

[Mr Skeptic]

Evolution can be seen as both ingeniously clever but simultaneously unimaginably stupid. There's plenty of examples of both.

[CharonY]

Punctuated equilibrium and gradualism are not really mechanisms, but just different and PE a slightly expanded viewpoints on the evolutionary history. Both are, in essence, descriptors for certain patterns. The mechanisms could be, in cases of PE, for instance the isolation of daughter populations.

[TonyMcC]

Would you not say that punctuated equilibrium may well be a possible cause for an abrupt evolutionary change of a species but if that changed species cannot flourish in the environment it finds itself it will probably not succeed? i.e. it must "fit" its environment?

[CharonY]

PE is the observation of a possibly rapid change, due to a variety of effects. It could very well caused by the occurrence of a strong selective pressure.

In that case a radical sweep through the population may occur resulting in a very different composition (as all with or without certain alleles essentially have low or no offspring) from a few generations back. This will then be observed as PE.

Of course, stochastic effects are also likely (maybe even more likely) causes.

 

PE is generally not that suddenly new phenotypes sweep through the population and are then selected. PE still relies on the gradual occurrence of mutations, for instance.

[D H]

Would you not say that punctuated equilibrium may well be a possible cause for an abrupt evolutionary change of a species but if that changed species cannot flourish in the environment it finds itself it will probably not succeed? i.e. it must "fit" its environment?

Hypothetical example: Suppose a population is spread over a relatively wide range, wide enough that some variations exist over the geographic area spanned by the population. There is nothing special in the environment that explains those variations. All that is needed to explain those variations is genetic drift. Now imagine that something happens that splits the population in half. A rising mountain range, an earthquake that diverts a wide river right through the middle of the population. Those two now-split populations will go there own way. The starting point of this deviation isn't "fitness"; it is just randomness.

 

Darwin was a 19th century scientist. Clockwork universe. Attributing all to "fitness" ignores that our universe is not a clockwork universe. Chaos appears even in a deterministic systems. Add in quantum randomness in DNA copying, random mutations caused by cosmic rays, etc., and "fitness" becomes a just tendency rather than the sole driver in evolution.

[TonyMcC]

I think I understand what you are saying. If the population is unchanged but split in the way you are describing then presumably the two halves (we shall assume split equally) will continue to evolve and in doing so eventually give rise to 2 seperate species. In their two separate territories they will have the same difficulties in surviving - finding nourishment and dodging predators etc.. Thus the trigger point for the arising of these two species was sudden. After the split gradual mutation will again have its place in the development of each species. Some of these mutations will be beneficial and aid survival although most will be detrimental. I hate to put it this way but surely it is true to say some of the mutations will make the mutated individuals "more fit" for survival and most will make mutated individuals "less fit". I don't think you disagree with this - I believe you wanted me to understand that gradual evolution via natural selection was not the only evolutionary pathway. If that was your aim then you have succeeded and I thank you. Although not as sudden and total a start as you have described Darwin's finches show seperate evolution after seperation from the original species.

[D H]

I don't think you do understand my point. The populations differed at the instant the river cut them off, and that difference had nothing to do with fitness.

 

So let's try something different. Suppose we wound the clock back by 600 million years (i.e., prior to the Cambrian explosion) and then let time go forward again. After letting that world run for 600 million years, would we see the same world that we do now? Stephen Gould, for one, didn't think so.

[TonyMcC]

Sorry - this exchage must be frustrating for you, but surely at the instant the river seperated the population both resulting populations were essentially the same. Perhaps you are saying that since all individuals have a unique DNA pattern, and since at the time of division some individuals would have carried mutated genes, the gene pool of each population is different? Perhaps that gives a different starting potential for each population? I can quite see that if the clock is wound back 600 million years and restarted then due to the random nature of mutations the life content of the world today would be very different. This obviously is a topic which I find interesting but have only a laymans knowledge - thank you for your patience.

[D H]

Google the term "genetic drift".

[Edtharan]

One of the main causes of punctuated equilibrium is that there exists local optimal fittnesses. That is it is posible for an organism to reach a point where any changes will cause it to be less fit, even though there is a "solution" (genetic code) that would allow them to be more fit for the environment than they currently are.

 

However two things can disrupt this:

1) Genetic Drift

With a large population you will get some degree of genetic drift, and this will cause the gene pool of the organism to spread out and even allow it to be "less" fit (but not significantly so) than the local optimum. Eventually this gentic drift will be enough that a mutation could cause a group to move outside the local optimum (may be in that it allows expansion into new territory) and into a large optimum across a local minimum fitness. This would then allow this "pioneering" group to eventually achieve a high level of fitness to the environment than the base group and thus split off from them into their own species.

 

As there are many traits that any organism has, there is a massive range for this to occur in, and which particular trait (or traits) eventually lead to an emergance from a local optimum

 

2) Changeing environment

In reality all environments are in a constant state of change, it is usually so slow that we don't notice it. However it is usually slow enough that evolution can adapt to these changes as they occur (although sudden ones like volcanoes are really hard to adapt to ). If a species has a local optimum that adapts them to one kind of environment, but then that environment slowly changes, then this can be the force that drives them out of a local optimum and evolution drive the organism's geneic codes to another local optimum. As the rate of evolution can be quite (relatively speaking as compared to the rate that environments typically change), then this sudden change will appear as a punctuated evolution.

[skyhook]

I don't get it. In my opinion, both punctuated equilibrium and gradualism( relatively gradual ) seems to be the same thing.

Darwin don't know about DNA in his days so it is more general, I don't find anything wrong.

 

A doubt is that if the deduction is based on observing fossils, and also living organisms, but if the newer theories are also based on doing statistics on bones, well er ...there is no useful DNA in fossils, and they say that the geological records are imperfect. When drawing a graph, If you have two points, you get a straight line. If you have 3 or more points , you may get a slight curve. so with limited samples, you may get straight lines.

 

The Ice age seems to be slow changes in environment over a long period. These are environmental changes which potentially affected creatures and plants. Right now we hear about global warming, and the polar bears are suffering. The change is very small, maybe 0.1units every decades or something. and it is not known if it will increase further or drop in future. I'm saying, there were drifts in environmental factors in the past. so creatures may have been constantly morphing to adapt to their environment or they die. and that is not the primary reason. There are several other reasons, chance, asteroids hiting earth causing a relatively abrupt changes. but generally, evolution seems to be a gradual slow process.

 

The definition of species is also complex. Species is a man-made word for classification purposes. While that is usually the case, some varieties can have morphological difference that they look like different species from the main group. but it is hard for me to name some examples. maybe the asian arowanas which live on different islands. Some hybrid cichlids can probably cross the species gap, with man's assistance. and the natural hybrids of tropical pitcher plants and orchids. We know the living organisms are diverging , but the past records from fossils are not fully known.

Edited October 22, 2010 by skyhook

[Darwinsbulldog]

I don't get it. In my opinion, both punctuated equilibrium and gradualism( relatively gradual ) seems to be the same thing.

Darwin don't know about DNA in his days so it is more general, I don't find anything wrong.

 

A doubt is that if the deduction is based on observing fossils, and also living organisms, but if the newer theories are also based on doing statistics on bones, well er ...there is no useful DNA in fossils, and they say that the geological records are imperfect. When drawing a graph, If you have two points, you get a straight line. If you have 3 or more points , you may get a slight curve. so with limited samples, you may get straight lines.

 

The Ice age seems to be slow changes in environment over a long period. These are environmental changes which potentially affected creatures and plants. Right now we hear about global warming, and the polar bears are suffering. The change is very small, maybe 0.1units every decades or something. and it is not known if it will increase further or drop in future. I'm saying, there were drifts in environmental factors in the past. so creatures may have been constantly morphing to adapt to their environment or they die. and that is not the primary reason. There are several other reasons, chance, asteroids hiting earth causing a relatively abrupt changes. but generally, evolution seems to be a gradual slow process.

 

The definition of species is also complex. Species is a man-made word for classification purposes. While that is usually the case, some varieties can have morphological difference that they look like different species from the main group. but it is hard for me to name some examples. maybe the asian arowanas which live on different islands. Some hybrid cichlids can probably cross the species gap, with man's assistance. and the natural hybrids of tropical pitcher plants and orchids. We know the living organisms are diverging , but the past records from fossils are not fully known.

 

Mayden (1997) lists about 22 concepts & definitions of species, as I recall: The biological species concept, the ecological species concept, the cladistic, the phylogenetic, the evolutionary, the morphological and so on. Mome of this invalidates the reality of species. With lots of modes of reproduction [asexual, sexual, budding, fission, LGT, etc] and inheritance, it is not surprising the life does not fit perfectly well into little boxes. Generally, the BSC is fine for most things except obligate asexuals.

 

Mayden, R. L. (1997). A hierarchy of species concepts: The denouement in the saga of the species problem. Systematics Association Special Volume Series; Species: The units of biodiversity: 381-424.

 

As to the gradualism vs PE thing. Darwin never said that things have to evolve at the same rate. We now know that great morphological changes can occur though very small modifications of Hox gene expressions with gene regulatory networks. So variable environments can lead to more evolutionary change than stable ones...no surprise there.

See these two papers by Emlen on Dung beetle horns:-

 

EMLEN, D. J. (2000). "Integrating Development with Evolution:A Case Study with Beetle Horns." BioScience 50(5): 403-418.

 

Emlen, D. J., L. Corley Lavine, et al. (2007). "On the origin and evolutionary diversification of beetle horns." Proceedings of the National Academy of Sciences 104(Suppl 1): 8661-8668.

Many scarab beetles produce rigid projections from the body called horns. The exaggerated sizes of these structures and the staggering diversity of their forms have impressed biologists for centuries. Recent comparative studies using DNA sequence-based phylogenies have begun to reconstruct the historical patterns of beetle horn evolution. At the same time, developmental genetic experiments have begun to elucidate how beetle horns grow and how horn growth is modulated in response to environmental variables, such as nutrition. We bring together these two perspectives to show that they converge on very similar conclusions regarding beetle evolution. Horns do not appear to be difficult structures to gain or lose, and they can diverge both dramatically and rapidly in form. Although much of this work is still preliminary, we use available information to propose a conceptual developmental model for the major trajectories of beetle horn evolution. We illustrate putative mechanisms underlying the evolutionary origin of horns and the evolution of horn location, shape, allometry, and dimorphism.

 

Hox and related gene clusters are highly conserved in evolution. They go back at least 500+million years to before the Cambrian Burgess Shale fauna. And yet they are flexible enough for great change and innovation to occur, via gene duplication, function gain, function loss, and subfunctionalization. For a detailed view, read:-

 

Carroll, S. B. (2005). "FROM DNA TO DIVERSITY: Molecular Genetics and The Evolution Of Animal Design". Oxford, Blackwell.

 

for a less technical account read:-

 

Carroll, S. B. (2005). Endless Forms Most Beautiful:The New Science Of Evo-Devo and the Making Of The Animal Kingdom. London, Phoenix.

 

Sex determining pathways [either genetic or environmental -such as temperature] can feed into the gene regulatory networks to express sexual dimorphic traits, as we saw in the Emlen papers above.

 

The mammal male sex determining gene on the Y chromosome is called SRY, and you can see how it interacts with the Hox network to produce sexual dimorphic features here:-

 

DiNapoli, L. and B. Capel (2008). "SRY and the Standoff in Sex Determination." Mol Endocrinol 22(1): 1-9.

SRY was identified as the mammalian sex-determining gene more than 15 yr ago and has been extensively studied since. Although many of the pathways regulating sexual differentiation have been elucidated, direct downstream targets of SRY are still unclear, making a top down approach difficult. However, recent work has demonstrated that the fate of the gonad is actively contested by both male-promoting and female-promoting signals. Sox9 and Fgf9 push gonads towards testis differentiation. These two genes are opposed by Wnt4, and possibly RSPO1, which push gonads toward ovary differentiation. In this review, we will discuss the history of the field, current findings, and exciting new directions in vertebrate sex determination.

 

and here:-

 

Foster, J. W., F. E. Brennan, et al. (1992). "Evolution of sex determination and the Y chromosome: SRY-related sequences in marsupials." Nature 359(6395): 531-533.

 

And Lance discusses sex determination in reptiles here:-

 

LANCE, V. A. (1997). "Sex Determination in Reptiles: An Update." American Zoologist 37(6): 504-513.

Sex determination and sex differentiation are two separate but related phenomena. Sex differentiation is a programmed cascade of events in which the indifferent gonad develops as a testis or an ovary with the appropriate urogenital and secondary sex characters. Sex determination is the event that sets this cascade in motion. In placental mammals, there is good evidence that sex is determined by a gene on the Y chromosome (SRY) that initiates testis formation. In the absence of SRY an ovary develops. There are, however, examples of placental mammal that develop as normal males with no detectable SRY. In reptiles, sex differentiation appears to be similar to mammals (i.e., the same genes and hormones act ina similar manner), but sex determination is clearly very different. Ovarian differentiation in placental mammals can occur in the absence of estrogen or an estrogen receptor. Ovarian differentiation in reptiles requires the presence of estrogen. In the absence of estrogen a testis develops. In TSD reptiles, embryos will develop as females when treated with estrogen even if eggs are incubated at male-inducing temperatures, and conversely, will develop as males when estrogen synthesis is blocked in eggs incubated at female-inducing temperatures. A number of other genes have also been shown to be important in mammalian sex determination. One of these genes, Sox9, which is expressed in differentiating mouse testis, has recently been found to be expressed in embryonic reptile testis. Other genes that appear to be common to both mammals and reptiles in the sex determining cascade are SF- 1, MIH, and possibly DAX-1. Current research is now focused on how the gene that produces the enzyme necessary for estrogen synthesis (aromatase) is regulated in the embryos of reptiles with genetic or environmental sex determination. Controversial issues in reptilian sex determination are 1) the role of the brain in gonadal sex determination, and 2) the role of steroid hormones in the yolk prior to sex determination

 

I hope that helps.

 

PS. There is also a very interesting paper by Airoldi, who has found that a single amino acid change can alter the ability to specify male or female organ identity!

 

Airoldi, C. A., S. Bergonzi, et al. "Single amino acid change alters the ability to specify male or female organ identity." Proceedings of the National Academy of Sciences.

The molecular mechanisms underlying the developmental processes that shape living organisms provide a basis to understand the evolution of biological complexity. Gene duplication allows biological functions to become separated, leading to increased complexity through subfunctionalization. Recently, the relative contributions to morphological evolution of changes to the regulatory and/or coding regions of duplicated genes have been the subject of debate. Duplication generated multiple copies of the MADS-box transcription factor genes that play essential roles in specifying organ identity in the flower, making this evolutionary novelty a good model to investigate the nature of the changes necessary to drive subfunctionalization. Here, we show that naturally occurring variation at a single amino acid in a MADS-box transcription factor switches its ability to specify male and female reproductive organs by altering its repertoire of protein–protein interactions. However, these different developmental fates are only manifest because of an underlying variation in the expression pattern of interacting proteins. This shows that the morphological outcomes of changes to protein sequence and gene expression must be interpreted in the context of the wider regulatory network. It also suggests an explanation for the surprisingly widespread duplications of some of the floral transcription factors.

Happy reading.

Edited October 22, 2010 by Darwinsbulldog

[TonyMcC]

Out of interest I have been reading up a bit on this subject. Wherever I have looked so far I get the impression that the likes of Darwin and Wallace are not believed to have been incorrect in their ideas. The general opinion seems to be that their ideas were not complete and modifications were needed to explain more completely the paths of evolution. The same IMO could be said of the likes of Newton and even Einstein concerning their theories. what puzzles me is why the likes of Newton and Einstein are revered whereas poor old Darwin is ridiculed and despised by so many people.

[Ophiolite]

what puzzles me is why the likes of Newton and Einstein are revered whereas poor old Darwin is ridiculed and despised by so many people.

I know of no biologists who have nothing other than deep admiration for the man. The only people I know who ridicule and despise him are ignorant, self righteous religious zealots with all the perception of dessicated rhubarb. Do you feel there are scientists, or those with scientific educations who have negative views of him? I'm intrigued.

[TonyMcC]

On reflection I have probably read too much into a comment by D H "In a sense, who cares what Darwin said", especially as he completes his sentence with "Darwin was the start, not the pinnacle, of modern biology". In mitigation I would say that this was a response to my understanding of the phrase "Survival of the fittest". At the time I thought I was being informed that my interpretation was either completely wrong or irrelevant. Sorry D H if I have slighted you.

Edited October 22, 2010 by TonyMcC

[pioneer]

Newton and Einstein developed rational models based on cause and effect, both of which can make very exact predictions. Darwin's theory of evolution is more empirical, and can not make accurate predictions of the future states, although it can show basic trends.

 

As an analogy, it would be like Newton's theory of gravity only saying the apple will fall to earth if it is thrown or dropped. However, we can not use it to predict distance or terminal velocity. That is still a mystery. At that level of theoretical utility, one would still thank Newton for this basic understanding, but one would want to take it to fruition.

 

However, if the traditionalists want to maintain, " it will fall theory and nothing else", those concerned with the progress of the theory, will have to figure out ways to break the traditionalists strangle hold over the common sense of the flock. Darwin gets stuck in the middle.

 

Darwin built a good solid foundation, but the house is still being built.

Edited October 22, 2010 by pioneer

[TonyMcC]

I very happy with Darwin in the middle. In fact I suspect that the people presently developing an understanding of evolution will in their turn find themselves "in the middle". Because of the random nature of evolution (random tries with rare successes) I find it hard to believe that solid predictions will ever be possible.

[pioneer]

The whole idea of random is an assumption or a result of an incomplete theory. Life, as we know it, needs water. Without water the cell can not function. Water is a huge variable that is not yet fully added to the analysis. The current theory by using primarily the organics as the main variables, will off by default, making the observation appear random.

 

Let me give an analogy to this theoretical effect. Say we drop objects in a vacuum. They will all accelerate at the same rate due to the gravity. But in practice, since we are not in a vacuum, there are other variables like wind resistance that can impact the rate of falling of objects. If we stick to only the vacuum theory, in practice we will observe different rates of falling, which appear random based on the weather conditions. That appearance of random is an illusion based on the theoretical assumption of a vacuum, which does not fully reflect reality. Once we add the other variable called wind resistance, what had appeared random, magically becomes more logical and predictable.

 

By not using the water to the degree of its impact in the cell, we assume the vacuum and ignore this wind resistance, so it appears to be random. Once water is included, there is cause and effect since the weight of the variables will better reflect the reality of the phenomena.

 

If you look at a seed, it is inanimate. To get life going we add water. If we let the seed dry out the life stops. If ignored water as being a variable in sprouting seeds, then it appears like seeds randomly sprout or not, based on only a random genetic mechanism. We lose this simple cause and effect.