Evolution

[deamonstar]

this link will lead you to the answers that you seek. check out the whole site... especially the taxonomy section.

 

http://www.ecotao.com/holism/huevo/

[Noah]

Just saw this in the news. Sorta related to the discussion

 

Chimps are human, gene study implies

 

Noah

[Concept]

Originally posted by: Daisy

I have several questions about evolution:

 

1. Why don't we see it happening now - whether it be spontaneous or longterm evolution, it appears to no longer take place (at least we cannot observe it happening now). There have been no significant physical changes in humans or animals in thousands of years. Why does the evolutionary process just seem to stop?

 

 

To answer that DAISY..

 

I was once watching the Animal Planet and came across a documentary about our beloved elephants. The feature followed a group of African elephants for quite some time and explained what the elephants would do and why they would do it. But what caught my eye the most was the fact that due to elephant poaching in the past 100 years or so, some elephants are beginning to be born WITHOUT tusks..and will not grow any. This HAS to be direct evidence of evolution in real time because there had to be some gene that triggered the newborn calves to not be born without tusks. I guess it could be related to the fact that elephants have such a great sense of long term memory that they can remember the times when their closest members were killed for their tusks.

 

Also, the elephants were seen visiting an elephant graveyard where a past loved one went to die and it's body was decomposed. The only thing left was the bones but what the elephants did just baffled me.. they began to remove the tusks and HIDE them from future poachers. Usually behind a bush or something like that, but it was a gesture to the poachers that they understand what was being done to them. For an animal to do those things could only suggest high intellingence compared to others.

 

Well that was my first post!

[sensabile]

Originally posted by: Concept

This HAS to be direct evidence of evolution in real time because there had to be some gene that triggered the newborn calves to not be born without tusks

 

I'm not disagreeing with that as such, nor am I agreeing with it, simply because you can't call that evidence without a lot more detail as to why calves are starting to be born without tusks.

 

Also, evolution is nothing to do with 'triggering' genes, as I think Tormod mentioned before, evolution is more like an error, mutation or such like that is beneficial that manages to stay in the gene pool long enough to become common.

 

The most likely cause of tusks not being present in new borns is probably because the previous use of tusks ceased to exist, I don't know enough about elephants to say what the previous use was but thats my best explanation.

 

(probably all seemed a bit hazy but I'm tired sorry )

[phoenix]

Originally posted by: Noah

 

Ok, if humans evolved from apes, why is it that nowadays there are still apes, there are humans, but not any creatures in a stage between "ape and man"?

 

 

If there were, wouldn't you still be asking this question? Due to the nature of sex, there has to be a missing link somewhere.

 

Greetz,

 

Phoenix

[Andrameleh]

I would like to contribute to your discussion with my opinion. From my point of view things went like this: In the elephant population during the last century there had been genes or a gene that expressed the lack of tusks you‘ve been talking about. These genes were not being expressed due to the dominative existence of the genes that coded the presence of tusks (in other words the new - borne without tusks had very slim chance to survive over its competitors brothers).

Things changed dramatically over the last few decades. The environmental pressure on the elephant species increased heavily mainly due to hunting. Lets see now how it goes from there: Adults were systematically killed even before young bulls had the opportunity to have offspring. As it can be expected the opposite happened with the few non-tusked individuals. The conclusion is obvious, a small population of elephants without tusks survived through the massacre and started to grow in numbers regarding the total number of their population. As this procedure went on its results were made more clear to us.

 

PS: I hope you excuse my poor English, you see I am posting from Greece.

[Tormod]

Thanks, Andrameleh - that's a great example of "survival of the fittest". "Fittest" does not necessarily mean "strongest", like in your example it is a matter of adaptation. It is often purely coincidental. Elephants that happen to be born without tusks are more likely to survive and grow old and have children.

 

And - welcome to our forums. Your English is perfectly fine.

 

Tormod

[Lord Henry Wotton]

Random Mutations, can they really account for the development of a human from a single celled organism? Does this not involve the addition and not merely the alteration of DNA? Has it ever been observed that a mutation add DNA?(not to the best of my knowledge)

 

Just a thought to ponder:

 

"What type of biological system could not be formed by "numerous, successive, slight modifications"? Well for starters, a system that is irreducibly complex. By irreducibly complex I mean a single system composed of several well-matched, interacting parts that contribute to the basic function, wherein the removal of any one of the parts causes the system to effectively cease functioning. An irreducibly complex system cannot be produced directly (that is, by continuously improving the initial function, which continues to work by the same mechanism) by slight, successive modifications of a precursor system, because any precursor to an irreducibly complex system that is missing a part is by definition nonfunctional. An irreducibly complex biological system, if there is such a thing, would be a powerful challenge to Darwinian evolution. Since natural selection can only choose systems that are already working, then if a biological system cannot be produced gradually it would have to arise as an integrated unit, in one fell swoop, for natural selection to have anything to act on. "

 

 

--Michael J. Behe in Darwin's Black Box

[Roberto]

Indeed, DNA may be added or substitued by virus or bacterias. The caul is a membrane that comes from a virus DNA that was incorporated in early organisms.

 

New cromossomes may appear. For example, there areh persons that have a triple X cromossome, but it does not give them any advantage and probably will not pass to their children. But at least it shows that this is possible in principle.

 

And there are a complete branch of physics and mathematics named Complexity Theory that studies the appearance of complex behaviour from simple rules. Have you ever heard about John Conway´s game of life? You can find it easily on the internet.

[Lord Henry Wotton]

Yes, I have heard of John Conway's game of life. I have studied this quite intently in mathematics class. Irreducibly complex systems that can be created by succesive generations in the Game of Life are very different to an irreducibly complex biological system. A biological system such as an animal consists of a massive variety of cells. The Game of Life is a dramatic simplification of such a system, and in this process of simplification it fails to simulate the truth.

Logically however, an irreducibly complex biological system cannot be created through succesive additions. It is quite absurd to think that a biological system of irreducible complexity can be a stage in a process of any sorts. The key here is a "stage in a process". In the Game of Life when the system becomes irreducibly complex the system does not advance. According to evolution an irreducibly complex system would advance none-the-less.

 

Has a beneficial addition of DNA ever been recorded? The most well known addition of chromosomes is in downs syndrom. This isn't beneficial.

[Roberto]

Well, the fact that Game of Life is a simplification is not an disadvantage, on the contrary, that´s an advantage, because it shows that even the simplest rules can create emerging behaviours.

 

The other argument about irreducible complexity is curious. Can you give a biological example of this for us to discuss? I´m trying to think of any, but the organisms I can imagine are not irreducibly complex, they are very robust to errors (accidents, diseases, mutations, etc.)

 

With respect to addition of DNA bringing useful adaptations, I told you about the caul, or placenta. But even if we could not find an example today, the only fact that you can have this type of event happening opens the possibility that there could be a useful addition. If I remmeber well, in the last email you asked if it was possible, and it is. If it could be useful, yes too.

 

I recomend the site: http://www.talkorigins.org/

 

I do not know if this specific question is answered there, but anyway, you can formute it here. There are a lot of experts there that could give you more accurate and modern answers than me.

[BIG-D]

is evolution and adapting the same?? i don't think we evolved from apes, but, i think we are adapting to our enviroment as it changes. like maybe becoming more civil.

[Roberto]

You should be careful with words when you talk about a technical matter. Adaptation, like any other word, can represent several concepts depending where it is applied. When we talk about adaptation in evolution we are talking about some advantage that was selected in a species by mean of natural selection, it is different from us becoming more civilized. Both are adapatations, but one is selected by the environment while the other is a result of a personal effort. The second is not transmitted to the next generations by genes, only by culture.

[BIG-D]

i don't think we evolved from like a fish though or apes. or why did not the other apes evolve?

[Roberto]

We didn´t evolved from apes, both of us evolved from the same ancestor. The ape is an evolution of that ancestor, but with different adaptations than us.

[BIG-D]

then why did we not all evolve the same??

[Roberto]

Because the mutations are randomic.