Replies to This Discussion

Permalink Reply by Nelson on March 4, 2011 at 12:18pm

natural selection, evolution's main mechanism (there are others- gene flow, genetic drift, sexual selection [itself a subtype of natural selection]), works like this:

from a few uncontroversial facts we derive natural selection.

-organisms reproduce more offspring than there are resources (food, mates, shelter, etc.) to support.

-organisms must compete for access to and control of the limited resources in order to survive.

-the characteristics of organisms of the same species vary within the species with some individuals being longer and larger or shorter and smaller; some having better eyesight or sense of smell; some being faster or having markings that afford it the ability to blend into its background or, conversely, stand out from its background and serve as a warning to would be predators. of course there are populations within the species that do and do not have certain characteristics.

-the characteristics of an organism that allow it to better compete and ultimately survive are coded in its genes and passed down to the next generation.

-in surviving, an organism is in a position to pass on its genetic code to subsequent generations, the same genetic code that increased its chances of survival and reproduction. this creates a survival differential in the species with the more successful population- the population with the characteristics that afford them the ability to better compete- reproducing more frequently than other populations within the species. before long you can see that the better competing population that reproduces more will make up the largest proportion of the population of the species or, indeed, come to out compete the other populations altogether such that the other populations go extinct. the species will then be said to have evolved.

 

here it is simplified and graphic:

you mentioned Dawkins' The Selfish Gene. Dawkins (but others before him had laid the groundwork or said much the same thing) said that we could easily explain many animal behaviors that were selfless and altruistic at the level of the individual by looking deeper, at the level of the gene. while the individual animal appeared to be doing something selfless it was a behavior that increased the gene's likelihood of survival and, as such, the gene could be said to be selfishly looking after its welfare by predisposing the individual to selfless behaviors.

so, for instance, in looking at cooperation we are forced to ask why an individual would waste energy cooperating when if it just concentrated on its own needs it could do just fine. and that we are forced to ask the question seems to be a violation of natural selection because it's an economical process that doesn't favor waste.

and the answer is that while cooperation seems funny at the level of the individual on natural selection, when we look at the gene level it makes perfect sense. cooperation increases the population's chances of survival and since genes exist in populations and not just in individuals genes can and do predispose individuals to behaviors that increase the reproductive fitness of the gene by increasing the likelihood that the population in which the gene occurs will survive.

the thing to be mindful of is that "selfish" is used totally metaphorically. there's no intent or motivation behind genes or behind natural selection. so, too, you should recognize that when i say "natural selection doesn't favor waste" i don't literally mean that natural selection favors anything in the sense that you or i favor something. it's just that words like these are helpful when explaining the dumb cold process.

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Permalink Reply by idcollapse Ra on March 5, 2011 at 7:49pm

Thank you so much Nelson for your detailed and easy-to-follow answer , I really appreciate that ...

Now the bees exmaple that Dawkins used makes sense , I took things literally and thereby couldn't grasp the meaning ... I am working on acquinting myself with the terminology of biolgy and hope that this will lead to a better understanding of such books !

  thanks again for your time Nelson

 

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Permalink Reply by Reg The Fronkey Farmer on March 4, 2011 at 3:14pm

There are also a few common misunderstandings with the concept. It is again nearly always by people who don’t take the time to understand it.

Creationists claim that it does not adequately explain how life on Earth began. How life started on the planet has nothing to do with the Theory of Evolution. That is the theory of Abiogenesis. Whether a god, aliens or a puddle of hot mud created life on the planet make no difference to the process of Evolution.

Evolution can and does explain very complex cellular structures without the need for a creationist god to appear. Evolution occurs over long periods of time (generally) but it has no long term objectives. It is only concerned with the present environmental conditions the organism finds itself dealing with now.

Variations and mutations can happen randomly at any stage. However it is not random if these mutations get passed on. If they are beneficial to this complex cellular structure then by the process of Natural Selection they get passed on to the next generation. This is done only at the genome level.

If it was done by Intelligent Design then the copying process would be flawless. If it was a flawless process then Evolution would never have occurred – only photocopies of the original are replicated. The process however is not flawless – that is because mutations and variations do occur. This one concept alone is enough to debunk the stupidity of the I.D. argument.

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Permalink Reply by idcollapse Ra on March 5, 2011 at 8:06pm

I see what you mean Reg ; so many non-religious scientist on a video I watched on youtube say that if there is a ''god'' , it cannot be the same god of nowadays religions or all the previous religions...they went further (joking) and said that aliens helped by providing the right conditions for The Primordial Soup .

Thanks Reg

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Permalink Reply by Mason on April 4, 2011 at 9:37pm

Evolution is change over time. Simple as that. The current theory of biological evolution states that all organisms are derived from common ancestral species as a result of a mechanism known as natural selection, with some influence from other factors.

The current mechanism for biological evolution that is supported by the greatest number of scientists is natural selection, the idea that in a given environment, the organisms most suited to that environment will survive and produce the most offspring.

There is currently a decent amount of debate within the scientific community as to whether or not natural selection is the only mechanism of evolution, or whether or not it is even the most influential mechanism in the evolutionary process. Some scientists point to sexual selection being far more important, and many others point out the importance of mutation. There are also efforts underway to identify other potential sources of variation in the evolutionary process. However, this debate does NOT show a lack of scientific support for EVOLUTION, just a question on the mechanism that produces such change. This debate is NOT support for ID or creationism (though they do like to paint it as such).

Evolution itself is well documented in the fossil record, as well as in laboratory settings. There is a good list of observed instances of speciation here: http://www.talkorigins.org/faqs/faq-speciation.html

The majority of the knowledge I have of evolution in the fossil record is in regard to human evolution. We share a common ancestral species with chimpanzees and bonobos. From that point, this ancestral species developed into what we commonly call the australopithicines, the genera Australopithecus and Paranthropus (ex. Australopithecus africanus, A. afarensis, Paranthropus robustus, etc), bipedal semi-hairless apes with slightly increased cranial capacities, which lived mostly in Africa about 4-2.5 million years ago. The australopithecines eventually developed into the genus Homo, of which we (Homo sapiens sapiens) are the only species still alive today.

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Permalink Reply by Robert Karp on April 5, 2011 at 9:43am

I agree with what Reg says, it's %100 fact.  In a recent blog post I also referred to the best contemporary proof of evolution were Richard Linski and his e.coli evolved literally before his team's eyes. If someone says to you "show me evolution", point to that and there is nothing they can say to refute it.

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Permalink Reply by Heather Spoonheim on April 5, 2011 at 10:12am

My understanding of the matter comes from having very little experience with any of the bio-sciences and only recently reading up on some general talking points.  Rather than a hard core declaration of 100% fact, I consider it better described as an absolute certainty that is continually being reinforced by an ever expanding understanding of the particular facts.  It seems to be a very very broad concept that has so many underlying mechanisms that I find it difficult to think of as a singular fact.  The difference may seem trivial to many, but when speaking to those of us who know so little about the subject I think stating it in those terms makes it easier to absorb just how broad the concept really is.

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Permalink Reply by Arcus on April 5, 2011 at 12:14pm

That actually has (at least) three totally different and plausible interpretations:

Evolution of our Universe?

Evolution of our Solar System?

Evolution of life on Earth?

Presumably you referring to the last, so I'll give it a shot (without using google or reading other responses!):

It starts with Abiogenesis, which is the study of how biological life started. Still a bit in it's infancy, there is good evidence of how the available molecules would arrange themselves to form the building blocks of life. Life as we know it is based on carbon, which is the most versatile (in forming chemical bonds) molecule and a natural building block. It would attract sugars and proteins, and eventually end up forming DNA. The DNA then attracted lipids to form a protective shell, thus forming the first proto-cells.

These carbon based cells needed carbon to replicate, which incidentally was quite common on the young earth due to volcaning activity. This process (via photysynthesis) released massive amounts of oxygen into the atmosphere, a molecule which has been shown to turbo-charge evolution of life. Cells which could "cooperate" with other cells had a higher probability of successful reproduction, and the march towards multi cellular life started. 

After this initial phase, there is very much repetition over a theme. As DNA replicates, there are always some small mistakes (mutations), and (more importantly) certain offspring may have different combination of alleles switched on and off creating genetic drift. As conditions changed throughout the Earth's history, these first multicelluar globs evolved into basic oceanic lifeforms, from which subsequent life can trace its roots. 

Certain traits proved to be better adapted to the environment and carriers of these traits would reprocreate more successfully than the average population. The less well adapted variants would eventually die out, and the highly adapted ones would continue to evolve, etc.

------------------------

I can probably write a lot more, but I think that should probably contain enough schoolboy mistakes for any evolutionary science literate person to get a good laugh. :)

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Permalink Reply by Reg The Fronkey Farmer on April 5, 2011 at 3:49pm

Mutations should not be considered “mistakes”. If cells are constantly dividing and replicating (passing on DNA) then mutations creep in. So if it happens once in a billion (that is a very small number on the genome level) a sequence in the DNA chain is altered. This may result in the mutation getting naturally selected or rejected depending on whether or not it is beneficial to the life (survival) of the organism. That decision is based upon the environment where the organism is living. It is really only this decision that is important as Evolution is only concerned with survival NOW in order to pass on its genetic code. Another way of looking at it is that Evolution has no long term goals.

One thing to bear in mind (sorry for repetition) and is a great one to hit the fundamentalists with is that Evoultion does not explain how life on Earth began. It has nothing to do with it. I have often heard them say “But the Theory of Evolution does not explain how life started”. No it does not is my reply because that is not what it is about. The fact that fire heats water does not explain why water freezes. It only seeks to explain how life evolved after it got started.

It can be a difficult idea to see clearly because it is based on changes made over time – usually a very long period of time. We generally cannot imagine what 100,000 years is like but life on Earth began over 500 million years ago. I have a few video on my page about evolution. I am not a Fronkey hunter for nothing you know !!!

I believe the word of this man

and this Woman

Ok Ok I have a thing for clever women

 

 

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Permalink Reply by Arcus on April 5, 2011 at 4:00pm

Thanks for correcting me.

I think I grasp the fundamentals of the concept, but yet oh so much to learn about it before having even the right to hold any objection to it, if I ever would.

I actually saw the last video linked before and left a statement which should have been a question: Couldn't her claim be contradicted by punctuated equilibrium?

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Permalink Reply by Reg The Fronkey Farmer on April 5, 2011 at 7:22pm

@ Arcus - Yes you have a very good case. Firstly, I would like to say that I am not a biologist and anything I know about Evolution is through self education. I do see a very strong case for Punctuated Equilibrium and I would suggest that it only occurs when there are rapid changes to the environment in which the specific organism lives. This is probably the case concerning the arsenic poisoned worms in the video (I posted above). They needed to evolve rapidly or die. When the ground became poisoned there was a population bottleneck and it is probably just random that they adapted quickly enough to survive and become a new species.

There is great merit to the idea of Punctuated Equilibrium. However it is still Evolution. It adds to the Theory and in no way suggests that Evolution over long periods of time is wrong. I shall learn some more on it.

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Permalink Reply by Kris Feenstra on April 6, 2011 at 2:51pm

In the bare minimum terms, a genetic trait simply needs to arise, and it needs to be propagated.  The mechanisms for both cases are numerous and varied.

 

disclosure: I'm simply using the worms as a hypothetical example because they're already on the table for conversation.  I have no idea how these worms actually evolved or what factors were at play.  

 

The trait for arsenic resistance in worms may have existed prior to arsenic contamination of their environment.  It could have been a trait that had neutral impact on individuals carrying it, insufficiently negative impact to hinder survival, or was beneficial in some other way.  The important thing is that individuals carrying the trait survive and propagate it, even if the trait itself is not immediately beneficial for survival.  

 

Now introduce arsenic into the environment.  The trait of arsenic resistance, even if only at a rudimentary stage of development suddenly becomes very relevant for survival.  Those worms carrying it are far more likely to survive and propagate.  Those worms not carrying it will not survive, no matter how fit they are by all other standards.  Depending on how much genetic variation there was in the overall population and how many worms were killed off in the arsenic, you may see a considerably change in the allele frequencies in the population inside the affected areas.  Some traits may disappear entirely from that population.  If you compare worms in the affected area to worms outside the affected area, you'll see different sets of selection factors being applied to groups with possibly different allele frequencies and different levels of genetic diversity.

 

I don't know that much about worm reproduction or genetic variation, but a hundred and seventy years is probably over one hundred generations.  That still seems like a remarkably short amount of time to diverge into a new species, but under those conditions, it seems somewhat plausible.

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