Evolution question

[Bergen]

( my first language isnt english so im sorry if theres alot of spelling errors )

 

first off im not a religious man and i DO " belive " in evolution theory, just to ease everone's mind

 

My knowledge admittedly on this topic is limited to what ive read in a few books/magazines and seen in documentaries so i am well aware that these questions may have been answered without me knowing it.

 

My question is about forknowledge, or what to me seems like forknowledge.

 

First i have hard time getting my head around how the first watercreatures could make the jump to land. How did they succesfully "aquire" the biology to survive in an enviroment it had not yet experienced ? i mean, how did they evolve a new system to aquire oxygen even tho they had no "idea" what they needed ?

 

My other question is similar but also evolves around time.

 

We know that certain animals etc evolved longer limbs, bigger teeth, smaller body's etc to better survive in their enviroment but from my understanding ( and i repeat that i may be way off ) most of these attributes takes 1000s of years to evolve. My question is that how did these creatures survive while they evolved their much needed "longer necks" ? And i would guess that in a couple of 1000years the enviroment around them would have changed so their evolution was to no avail, to me that seems to have an unbearable failrate , so is it pure "luck" when they evolve in the right direction ?

 

i hope these questions wasnt to nOOb for you guys as im a major in computer science and this really isnt my field at all. And again im no creationist i just got stuck on these questions when i pondered it.

 

thx

[Horza2002]

Im no expert but heres some of my thoughts.

 

For your first one, any animal that lived in shallow water that had a high silt suspension could have found a way to acquire oxygen by jumping out of the water and landing back in again (i.e. the silt could have affected there gills etc). Therefore animal that had better air breathing systems would have urvived better...keep that going until they could live on land where they'd find so much food because no other animal lives on the land and there you have it.

 

The second u need to remember that just because an animal is not perfectly adapted to an environment doesnt mean it'l die in it. All that means is that the animals with longer necks had a better chance to survive than those with shorter ones.

[Sisyphus]

It is true that there is never any foreknowledge. Organisms do not evolve traits so that in the future they will be useful, they can only evolve traits that are immediately useful.

 

I don't know much about the specific examples you give. You might want to look at things like lungfish, which are kind of an intermediate step between ocean fish and amphibian-like creatures.

 

Also remember that no environment is static. Organisms evolve alongside the environments they live in, which includes other organisms who are also evolving, and even themselves. It would not be surprising at all if the ancestor of a particular species could not survive in a modern environment, but could in its own.

[Ontogeny]

Hello Bergen,

 

I think the main point to remember is that there is no 'forknowledge' in evolution, everything you see around you is the result of the generally very slow adaptation of animals to changes in their environment.

 

Animals never 'needed' longer necks as such, but the animals whos necks happened to be longer due to small genetic changes would have been better able to take advantage of ecological niches in which food was more readily available to them and those animals would have been able to survive more easily than the ones who had to compete for more limited resources at ground level for example.

 

It follows that animals with longer necks who live in areas with trees, let's talk Giraffe for example, would be able to survive and produce and feed offspring more readily as well and their genes would be passed on to their offspring and so on and so on...slowly developing the longer necks we see today and mind you this process would have taken many generations to take place...

 

We need to remember that changes in the evironment lead to the opportunity for change and many animals and possibly humans included never manage to adapt to change as fast as necessary to ensure the survival of a species!

[ewmon]

Perhaps the Lundehund provides an excellent example of natural selection.

 

 

[The lundehund] represents perhaps the most valuable material for scientific investigation of how a species can modify itself to its specialized milieu.

 

This long webpage is worth reading: The lundehund

[CharonY]

[The lundehund] represents perhaps the most valuable material for scientific investigation of how a species can modify itself to its specialized milieu.

 

Species do not modify themselves (in some cases they enhance mutation rates, but that is about the scope of it). In the simplest scenario variation exist and the most advantageous traits manage to propagate.

In case of dog breeds however, generally artificial selection is prevalent. I.e. the breeder chooses what traits he likes and allow those to propagate, regardless whether the trait allows is connected to reproductive success in natural context or not. Under natural selection conditions only traits are selected that allow for an advantage in terms of propagation.

[Moontanman]

Perhaps the Lundehund provides an excellent example of natural selection.

 

 

 

 

This long webpage is worth reading: The lundehund

 

Thats a good looking dog but no Dog is the result of natural selection, they are all the result of human selection. I keep Basset hounds, I could relate many traits that are unique to basset hounds but all of them are the result of humans choosing them in some way, if for no other reason it's because the dogs do their jobs or look better than their siblings and are the only dogs allowed to reproduce.

 

Domestic dogs are not the result of natural selection they the result of intelligent design, ours!!!

[ewmon]

IMO, the traits of the Lundehund came about through natural evolution accelerated by human intervention.

 

I find it hard to believe that people sat down and said that they needed a dog with useful dewclaws, ears that fold shut, shoulder joints that splay, a hyperextending neck, etc, so let's breed some dogs in that direction. The special situation here being that the caves proved to be a literal "black box" in which the means by which certain dogs excelled more than others could not be humanly discerned (since obviously, humans could not even go where these dogs go).

 

Instead, I think people noticed that some dogs came out of these caves with more puffins than other dogs, so they kept breeding the successful ones and using them and refining them. My point being that natural selection would have driven the breed toward having these traits if shipwrecked on puffin-inhabited islands without humans. Nature worked out the necessary characteristics; people simply accelerated the process.

Edited July 1, 2010 by ewmon

[pioneer]

There is a cause and effect between environmental potentials and some aspects of evolution. For example, if the earth's atmosphere changed, we know many aspects of life would need to change to meet the new demands, with selective advantage going to those who can make the best of the new atmosphere. Even before we begin the biological process of change, we know the gist of where evolution needs to go and will go.

 

For example, we use antibiotics. This is a man-made hostile environmental potential we are setting for the bacteria. I bet the goal of bacteria evolution will be connected to lowering this potential; building resistance.

 

If we use the traditional evolutionary theory, which assumes evolutionary change has no cause and effect toward a goal, this would imply the bacterial resistance to these drugs will be a random crap shoot, with the odds of them learning to sing just as likely. This assumption of evolution may be why antibiotics were over used, since what are the odds of them achieving a well defined goal at the level of the DNA?

 

Relative to sea creatures learning to walk. The two paths are random or we can set a potential so this new behavior is a way to lower a life threatening potential. For example, the body of water begins to dry up into smaller pools, with the critters getting crowded in the pools; puddle hoppers.

[cypress]

My question is about forknowledge, or what to me seems like forknowledge.

 

First i have hard time getting my head around how the first watercreatures could make the jump to land. How did they succesfully "aquire" the biology to survive in an enviroment it had not yet experienced ? i mean, how did they evolve a new system to aquire oxygen even tho they had no "idea" what they needed ?

 

The classical view of neo-Darwinian evolution including gradual change over time is finally giving way to a modern synthesis which in some ways is beginning to acknowledge that significant changes including your example likely involve mechanisms that do not fit the model of natural selection of genetic errors. There are newer models based on evidence of nonrandom genetic changes induced by environmental and perhaps other influences. You are quite justified in wondering how blind random processes might generate novel systems without "forethought". Experimental biologists are increasingly examining the limits of random genetic error to produce the quantity and diversity of genetic changes to feed the number of protein interactions, gene controls and developmental controls require for new cell level biochemical processes. Population genetics when applied to the number of changes is demonstrating that the number of alterations do not happen in the timeframes indicated by the fossil evidence.

 

My other question is similar but also evolves around time.

 

We know that certain animals etc evolved longer limbs, bigger teeth, smaller body's etc to better survive in their enviroment

 

We actually don't know this, we speculate this is true. Take the Giraffe's neck for example. If neck length is explained by selective advantage how does one account for the fact that female giraffe's are about two feet shorter than males? What part of selective advantage accounts for that? There are a host of other major issues involving the need to coevolve a large number of required subsystems with this concept I don't intend to get into in this reply, but again this model seems seriously deficient in terms of explanatory power. It is an elegant narrative but it does not seem to match the facts. We are in need of a better more coherent process.

 

but from my understanding ( and i repeat that i may be way off ) most of these attributes takes 1000s of years to evolve. My question is that how did these creatures survive while they evolved their much needed "longer necks" ? And i would guess that in a couple of 1000years the enviroment around them would have changed so their evolution was to no avail, to me that seems to have an unbearable failrate , so is it pure "luck" when they evolve in the right direction ?

 

This is another reason to be suspicious of the classical model. Again, the example of experimental biology and population genetics indicates you are correct to question this.

 

i hope these questions wasnt to nOOb for you guys as im a major in computer science and this really isnt my field at all. And again im no creationist i just got stuck on these questions when i pondered it.

 

thx

 

I would not have a problem even if you were a creationist, you are asking questions that don't currently have very good answers. Progress is being made but I suspect the classical ideas are in need of an overhaul.

[CharonY]

Ahem. The modern synthesis was coined in the 40s. Not quite recently. I will respond to the op a bit later, if I remember. Have to finalize some stuff first.

[Ontogeny]

'We actually don't know this, we speculate this is true. Take the Giraffe's neck for example. If neck length is explained by selective advantage how does one account for the fact that female giraffe's are about two feet shorter than males? What part of selective advantage accounts for that?'

 

 

How about sexual selection? Intrasexual selection accounts for the difference in body size between males and females of the species!

Edited July 4, 2010 by Ontogeny
make the quote more obvious

[Sisyphus]

Sexual dimorphism of all sorts is an expected result of natural selection. Sexual selection accounts for a lot of it, but not necessarily all. Since the life of a male is necessarily different from the life of a female - in some species much more than others - different selection pressures apply, that are often not immediately obvious.

 

As for giraffes, I know males fight over females by whipping their heads into one another. You can see it on youtube - it's simultaneously ridiculous and kind of terrifying. That alone could account for males' longer necks, I reckon.

 

Though I'm just speculating. As I said, it's often not immediately obvious. Just because you can't see the selective advantage of something doesn't mean there isn't one. Evolution tends to be a lot more subtle and complex than the simplistic narratives we tend to come up with, such as trends that look "planned" (or badly planned, in a lot of cases) in hindsight.

Edited July 4, 2010 by Sisyphus

[Bergen]

thanks for all the good answers !

[Darwinsbulldog]

This is a very interesting question, because it is obvious that we humans are both products of blind evolution and yet have the ability to model the future. So unless we want to go down the path of using a supernatural cause [which is unscientific anyway] we are left with natural causation somehow producing a self-aware species such as ourselves. This gives the illusion of a self-forfilling prophesy!

 

So, if we take the Dawkins idea of genes building bodies to protect themselves so that they can replicate, then we have the essence of the answer. Replicates are seldom perfect copies, and thus there is variation. Variation is subject to natural selection and so we get organisms acquiring information about their environment. [but not, at least initially, understanding]. Thus a bear born with thick fur in a cold country "knows" something about it's environment. [All the "bald" bears, we presume, would suffer reduced survival and reproduction compared to the hairy bear.]

 

But let's backtrack to the original putative proto-cell. Some sort of sensation-response network needs to be set up. This is done by chemical signaling. A cell membrane polypeptide might respond to -say- acidic conditions. As too much acid [or perhaps too little] would kill the cell, any variations in the polypeptide that improved it's pH detection capability would be favoured by selection. So would any linkage between this "key and lock system" with a protein that produces a response.

 

Survival might be further enhanced by putting a "decision" phase between detection and response. Perhaps a chain of molecules that allowed various "options", or a flexible response, perhaps by the liking of different biochemical "detection" and response molecules.

 

With the evolution of multicellularity, different cells could first adhere together, and then differentiate in function. Chains/networks of cells that depolarised their membranes in response to physical stimulii would evolve into nerves. Nerves give "real-time" information about the environment, as well as inherited information as I outlined in the bear example.

 

As nerves congregated into ganglia and eventually brains, the integration and processing of different senses gave the organism even more real time information about it's environment. Such a sophisticated sensory and processing network would eventually lead not just to a good model of external [and of course internal] environmental states, but any "spare" processing ability could produce or predict possible or likely future environmental states. This is because brains can store historical information, and thus the organism will be aware of history [it's own and the external] , and in particular, recurrent patterns or cycles. For example, the seasons or day and night. We can thus easily imagine that consciousness could emerge from this process. Thus over the eons, genes learnt to build bodies that could see into the future, even though they themselves have no idea what they are doing.

 

Of course, organisms can do fine without intelligence, but sensory organs do appear to be universal, and sight is present in about 95% of animals species. Spiders and sharks are not known for their intellectual prowess, and yet they proser very well, so I do not want to give the impression that intelligence was inevitable, just a viable way of making a living among many. Plants do very well without animal senses or brains, although they do sense their environment chemically and sense light without vision.

 

Thus their is a tiny grain of truth in creationists creotards, but for a different reason than the ones they postulate. If there is no supernatural creator, then the whole process must be natural. What I have outlined above is highly speculative, and many details are not confirmed or even known. But given the efficacy of organic evolution-the fact of evolution, it seems likely that both chemical evolution [abiogenesis] and the evolution of consiousness requires no intervention of gods at all, but are entirely products of nature.

 

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'We actually don't know this, we speculate this is true. Take the Giraffe's neck for example. If neck length is explained by selective advantage how does one account for the fact that female giraffe's are about two feet shorter than males? What part of selective advantage accounts for that?'

 

 

How about sexual selection? Intrasexual selection accounts for the difference in body size between males and females of the species!

 

Any question about morphology will probably involve an answer in terms of Hox gene activity and expression. In the case of sexual dimorphism therefore, we can expect that any morphological differences between the sexes would involve an interaction of Hox and sex determining genes to produce differential outcomes in the embryos in each sex. In humans for example, the organismal bauplan is female, and the downstream gene expression of the master sex determination SRY gene seems to be modifying parts of the bauplan for male morphology and functionality.

 

These are only proximate rather than ultimate answers, but perhaps a few papers will shed more light on the subject.

 

This paper, by Sandie M. Degnan, Bernard M. Degnan (2006) "THE ORIGIN OF THE PELAGOBENTHIC METAZOAN LIFE CYCLE: WHATS SEX GOT TO DO WITH IT? [Oxford University press] shows how sex itself may have evolved:-

 

The biphasic (pelagobenthic) life cycle is found throughout the animal kingdom, and includes gametogenesis, embryogenesis, and metamorphosis. From a tangled web of hypotheses on the origin and evolution of the metazoan pelagobenthic life cycle, current opinion appears to favor a simple, larval-like holopelagic ancestor that independently settled multiple times to incorporate a benthic phase into the life cycle. This hypothesis derives originally from Haeckels (1874) Gastraea theory of ontogeny recapitulating phylogeny, in which the gastrula is viewed as the recapitulation of a gastraean ancestor that evolved via selection on a simple, planktonic hollow ball of cells to develop the capacity to feed. Here, we propose an equally plausible hypothesis that the origin of the metazoan pelagobenthic life cycle was a direct consequence of sexual reproduction in a likely holobenthic ancestor. In doing so, we take into account new insights from poriferan development and from molecular phylogenies. In this scenario, the gastrula does not represent a recapitulation, but simply an embryological stage that is an outcome of sexual reproduction. The embryo can itself be considered as the precursor to a biphasic lifestyle, with the embryo representing one phase and the adult another phase. This hypothesis is more parsimonious because it precludes the need for multiple, independent origins of the benthic form. It is then reasonable to consider that multilayered, ciliated embryos ultimately released into the water column are subject to natural selection for dispersal/longevity/feeding that sets them on the evolutionary trajectory towards the crown metazoan planktonic larvae. These new insights from poriferan development thus clearly support the intercalation hypothesis of bilaterian larval evolution, which we now believe should be extended to discussions of the origin of biphasy in the metazoan last common ancestor.

Source:-

http://elibrary.ru/i...asp?id=10215273

 

This next source specifies an example of the connection between SRY and Hox:-

 

Barmina, O. and A. Kopp (2007). "Sex-specific expression of a HOX gene associated with rapid morphological evolution." Developmental Biology 311(2): 277-286.

Animal diversity is shaped by the origin and diversification of new morphological structures. Many examples of evolutionary innovations are provided by male-specific traits involved in mating and sexual selection. The origin of new sex-specific characters requires the evolution of new regulatory interactions between sex-determining genes and genes that control spatial patterning and cell differentiation. Here, we show that sex-specific regulation of the HOX gene Sex combs reduced (Scr) is associated with the origin and evolution of the Drosophila sex comb -- a novel and rapidly diversifying male-specific organ. In species that primitively lack sex combs, Scr expression shows little spatial modulation, whereas in species that have sex combs, Scr is upregulated in the presumptive sex comb region and is frequently sexually dimorphic. Phylogenetic analysis shows that sex-specific regulation of Scr has been gained and lost multiple times in Drosophila evolution and correlates with convergent origin of similar sex comb morphologies in several independent lineages. Some of these transitions occurred on microevolutionary timescales, indicating that HOX gene expression can evolve with surprising ease. This is the first example of a sex-specific regulation of a HOX gene contributing to the development and evolution of a secondary sexual trait.

 

Source [full paper downloadable] at:-

http://www.eve.ucdav...Kopp%202007.pdf

 

This paper outlines the process in fruit flies:-

 

Ng, C. and A. Kopp (2008). "Sex Combs are Important for Male Mating Success in <i>Drosophila melanogaster</i&gt." Behavior Genetics 38(2): 195-201.

ABSTRACT:-

The sex comb is one of the most rapidly evolving male-specific traits in Drosophila, making it an attractive model to study sexual selection and developmental evolution. Drosophila males use their sex combs to grasp the females' abdomen and genitalia and to spread their wings prior to copulation. To test the role of this structure in male mating success in Drosophila melanogaster, we genetically ablated the sex comb by expressing the female-specific isoform of the sex determination gene transformer in the tarsal segments of male legs. This technique does not remove the sex comb entirely, but simply restores the morphology of its constituent bristles to the ancestral condition found in Drosophila species that lack sex combs. Direct observations and differences in long-term insemination rates show that the loss of the sex comb strongly reduces the ability of males to copulate with females. Detailed analysis of video recordings indicates that this effect is not due to changes in the males' courtship behavior. Rapid evolution of sex comb morphology may be driven either by changes in female preferences, or by co-evolution between sex combs and female external genitalia.

SOURCE AVAILABLE AT:-

http://www.eve.ucdav...Kopp%202008.pdf

 

So from these examples, we can see how sex determining genes and Hox Gene Clusters [Gene Regulatory Networks] can interact to produce sexual dimorphic traits.

----

Here is another paper:-

http://www.ncbi.nlm....les/PMC2597198/

Williams, T. M., J. E. Selegue, et al. (2008). "The Regulation and Evolution of a Genetic Switch Controlling Sexually Dimorphic Traits in Drosophila." 134(4): 610-623.

Sexually dimorphic traits play key roles in animal evolution and behavior. Little is known, however, about the mechanisms governing their development and evolution. One recently evolved dimorphic trait is the male-specific abdominal pigmentation of Drosophila melanogaster, which is repressed in females by the Bric-à-brac (Bab) proteins. To understand the regulation and origin of this trait, we have identified and traced the evolution of the genetic switch controlling dimorphic bab expression. We show that the HOX protein Abdominal-B (ABD-B) and the sex-specific isoforms of Doublesex (DSX) directly regulate a bab cis-regulatory element (CRE). In females, ABD-B and DSXF activate bab expression whereas in males DSXM directly represses bab, which allows for pigmentation. A new domain of dimorphic bab expression evolved through multiple fine-scale changes within this CRE, whose ancestral role was to regulate other dimorphic features. These findings reveal how new dimorphic characters can emerge from genetic networks regulating pre-existing dimorphic traits.

Edited August 27, 2010 by Darwinsbulldog