Has evolution actually been observed?

[JerryClower]

Not trying to "troll" or anything of that nature, but no human has ever seen any type of mammal give birth to a slightly different mammal. How can an animal of one species produce an entirely different species? I know that it is gradual changes over time, that is why nobody has ever seen it happen. But what I'm asking is, how can an organism have offspring of a different species, like the theory of evolution states? Don't most scientists believe that all life forms present today evolved from other life forms? How is that even possible? Someone needs to tell me, don't most scientists believe that all land animals came from prehistoric life forms found in the ocean?

Also a question about natural selection. In natural selection, does the DNA of the organism actually "recognize" it needs to make a change, and then change. Or does natural selection just mean that an organism with the best sight and hearing (example) will be most likely to reproduce so then it will pass the 'best' sight and hearing onto its offspring. Eventually, over a lot of years, an organism will be produced that has great sight and hearing, since the organisms with the best sight and hearing are the ones that mated and reproduced offspring. Am I right?

 

[DanP]

Also a question about natural selection. In natural selection, does the DNA of the organism actually "recognize" it needs to make a change, and then change. Or does natural selection just mean that an organism with the best sight and hearing (example) will be most likely to reproduce so then it will pass the 'best' sight and hearing onto its offspring. Eventually, over a lot of years, an organism will be produced that has great sight and hearing, since the organisms with the best sight and hearing are the ones that mated and reproduced offspring. Am I right?

DNA doesn't know anything. It doesn't know it has to change.

When individuals in a population reproduce with different chances of success, hence some individuals contribute to the subsequent generations more offspring, allele frequency in the population change in such a way that it *adapts individuals* to the environments which influenced reproductive success. This is natural selection in a nutshell.

So yeah, basically it means your 2nd option.

 

[DanP]

Someone needs to tell me, don't most scientists believe that all land animals came from prehistoric life forms found in the ocean?

If you are interested in this, I think it would be interesting for you to explore a bit the theories about the colonization of land with photosynthetic organisms which lived in seas. It's really a important moment, and it illustrates many limitations said organisms had initially when moving to land (shores) , and the many adaptations required to actually move to totally dry land.

I think its very interesting to read about it.

 

[zomgwtf]

DNA doesn't know anything. It doesn't know it has to change.

When individuals in a population reproduce with different chances of success, hence some individuals contribute to the subsequent generations more offspring, allele frequency in the population change in such a way that it *adapts individuals* to the environments which influenced reproductive success. This is natural selection in a nutshell.

So yeah, basically it means your 2nd option.

The DNA doesn't know anything but it does recognize various things including mutations and organism can recognize when gene expression needs to change. It doesn't 'control mutations' as such however.

Not trying to "troll" or anything of that nature, but no human has ever seen any type of mammal give birth to a slightly different mammal. How can an animal of one species produce an entirely different species? I know that it is gradual changes over time, that is why nobody has ever seen it happen. But what I'm asking is, how can an organism have offspring of a different species, like the theory of evolution states? Don't most scientists believe that all life forms present today evolved from other life forms? How is that even possible? Someone needs to tell me, don't most scientists believe that all land animals came from prehistoric life forms found in the ocean?

We've never seen the birth of a slightly different mammal? Wonder it means to have a birth defect then...
You will need to define to me what species means there are so many various definitions floating around the scientific world it's hard to keep them all straight and give a 'definitive answer' to your question.

They have offspring the same way they have their other offspring... the catch of course being they have been mutated... which has been documented MANY times so I hope you won't try to dispute this.
Yes most scientists believe that all life forms present today evolved from other life forms. (If we include that life forms are no longer being created.)
It's very easily possible. Ask more specific questions and I can give you much more specific answers.
If we go far enough back in common ancestors yes, we will go allllll the way back to ocean life forms.

 

[CRGreathouse]

Not trying to "troll" or anything of that nature, but no human has ever seen any type of mammal give birth to a slightly different mammal.

Happens all the time. Where do new dog breeds come from? What about birth defects? What about disease immunities (including recent, and I believe novel, genetic resistance to HIV)?

How can an animal of one species produce an entirely different species? I know that it is gradual changes over time, that is why nobody has ever seen it happen. But what I'm asking is, how can an organism have offspring of a different species, like the theory of evolution states?

Of course speciation is not particularly well-defined, or rather there's not much agreement about what a good definition would be. But in short, change is incremental enough that A could mate with B, B could mate with C, ..., and Y could mate with Z, but A cannot mate with Z. (That is, "can mate with" or "is the same species as" are not actually transitive relations.)

The well-known example of a ring species gives an unrelated illustration of the concept. Letting <--> mean "is fertile with" or "is the same (biological) species as", we have
Herring Gull <--> American Herring Gull <--> East Siberian Herring Gull <--> Birula's Gull <--> Heuglin's gull <--> Siberian Lesser Black-backed Gull
but
Herring Gull <-/-> Siberian Lesser Black-backed Gull.

This is similar to the linguistic concept of a dialect continuum, if you're familiar with that.

Someone needs to tell me, don't most scientists believe that all land animals came from prehistoric life forms found in the ocean?

Sure, but that's not a hard transition. The 'recent' (~50 Ma) ancestors of dolphins were land-dwellers, whereas the transition from sea to land was much further back (~450 Ma).

Also a question about natural selection. In natural selection, does the DNA of the organism actually "recognize" it needs to make a change, and then change.

Never.

Or does natural selection just mean that an organism with the best sight and hearing (example) will be most likely to reproduce so then it will pass the 'best' sight and hearing onto its offspring. Eventually, over a lot of years, an organism will be produced that has great sight and hearing, since the organisms with the best sight and hearing are the ones that mated and reproduced offspring. Am I right?

Not particularly, but that's closer than the idea that DNA "wants" something and does it.

Natural selection is just this: what creatures live, live. If having eyes was a deadly disadvantage for some reason, then lots of creatures with eyes would die. Then most existing creatures would be eyeless, either because they survived the Great Eye Purge or because their parents (etc.) did.

If eyes provide no particular advantage but cost a lot (metabolically speaking), then there's some selection pressure away from eyes. When food is plentiful, creatures with eyes survive and reproduce just fine; when scarce, they're more likely to die off. Thus creatures in environments not friendly to eyes (e.g., naked mole rats) have, over a long course, selected against expensive (in terms of disease as well as development) large eyes. In environments where eyes are an advantage, the selection is in the opposite direction. A gazelle with poor eyesight might have trouble escaping predation, in which case it fails to pass along its genes.

Most novel developments (whether mutations or simple cross-breading) are either harmful or essentially neutral. Sometimes several apparently neutral developments, when combined, have an effect; in these cases that effect can be selected for or against.

 

[DaleSwanson]

Not trying to "troll" or anything of that nature, but no human has ever seen any type of mammal give birth to a slightly different mammal. How can an animal of one species produce an entirely different species? I know that it is gradual changes over time, that is why nobody has ever seen it happen. But what I'm asking is, how can an organism have offspring of a different species, like the theory of evolution states? Don't most scientists believe that all life forms present today evolved from other life forms? How is that even possible? Someone needs to tell me, don't most scientists believe that all land animals came from prehistoric life forms found in the ocean?

http://www.codeproject.com/KB/GDI/win32_Gradients/grad.jpg

That is a color gradient from red to orange to yellow. I don't think anyone would deny that it is red at the start then changes to orange then to yellow. However, where does it exactly change? You can't draw a line and say everything to the left of this is red. Well you could but it would be completely arbitrary. Same with evolution. If you looked at the family line going back millions of generations you'd see that the organism at the start wouldn't be the same species as the one at the end. To put it in our analogy the starting organism would be "red" and the ending would be "yellow". They would be undeniably different. However, at no single generational change would there be any significant difference. No parent would be a different species than its offspring.

 

[DanP]

Of course speciation is not particularly well-defined, or rather there's not much agreement about what a good definition would be. But in short, change is incremental enough that A could mate with B, B could mate with C, ..., and Y could mate with Z, but A cannot mate with Z. (That is, "can mate with" or "is the same species as" are not actually transitive relations.)

The A cannot mate with Z is misleading IMO. A better formulation would be "group A is separated by group Z with which interbreeding does not *usually* occurs".

I use the term "usually", because there are many examples of inter species breeding. Some there given in this very thread.

Anyway, this whole blur is caused by the fact we still have no perfect definition of "species".

to OP -- read this: http://en.wikipedia.org/wiki/Species_problem

 

[Philosothink]

I don't think a poor chihuahua male will ever be able to naturally have intercourse with a German Shepard female , for example. Though the opposite may be true (no ideea really :P) in some twisted situation :P[/QUOTE]


I can personally attest to this being incorrect... as a child i had a pet chihuahua, he was a terrible philanderer and would routinely go "off chasing" for days or even weeks! He'd come home weak and tired. On one outing, he indeed, entered the garage of someone our family knew. The door was raised several inches for airflow, and inside was a female german shepard, in heat... ugliest puppies ever... all middle sized, with mixed short and long hair.

 

[Philosothink]

Not trying to "troll" or anything of that nature, but no human has ever seen any type of mammal give birth to a slightly different mammal. How can an animal of one species produce an entirely different species? I know that it is gradual changes over time, that is why nobody has ever seen it happen. But what I'm asking is, how can an organism have offspring of a different species, like the theory of evolution states? Don't most scientists believe that all life forms present today evolved from other life forms? How is that even possible?

*****************

Jerry, you have a deep misunderstanding, or are deliberately being obtuse for the sake of argument. NO SCIENTIST, sane at least, believes that any animal ever gives birth to the offspring of another animal. It would have to be an embryo implanted into a similar animal, for the sake of scientific study, or possibly extinct species revival.

Only NON scientists think man evolved from apes, or use it as an argument.

Species differentiation requires many thousands (or hundreds of) of years in almost every case.

I trust time will clear all this up, and in the meantime, there will be a robust surplus of ignorant discussion on the matter.

 

[Philosothink]

Also,

"how can an organism have offspring of a different species, like the theory of evolution states?"

would you please elaborate to the rest of us, where you came upon this notion? It does not state this. At all. Only a person who had not read about Evolution on their own, and had derived their understanding of Evolution from the writings or verbalizations of others, who did not understand it would think this.

I recommend you actually read "Origin of Species". I it will clear up a lot of things for you. It can change your life for the better. And you can continue to believe in whatever magical beings you chose, because they are not exclusive of one another.

What right thinking all powerful being, would create life unable to adapt and change. Frankly, even when I was a christian, I was offended that people thought my god was too stupid to plan ahead for long term environmental changes.

The true danger of the Young Earth Theory is it requires mankind to embrace it's special place in the ecosystem and deny 200,000 years of natural selection, and the impact of that selection upon our body, and mind.

I will give you a key example. The Theory of Romantic Love. Our misunderstanding of biological mating preference and the function of the underlying mental systems, has caused needless deaths in acts of jealous passion, since the beginning of our kind and continues to this day. Our misunderstanding of these things, leads to nearly all teen pregnancies. Marriages fall apart when one spouse encounters someone they "can't resist" ... if only they understood their own minds. Love is a biochemical process which evolved for the purpose of ensuring the survival of our offspring.

I will fess up to my own non-scientistness here publicly. I am not formally educated on this matter, but I have read widely on it and prefer studying about myself to watching TV, so I'm not entirely unknowledgable, but a amateur no less. My commentary on this matter isn't typed out of a need for argument, i can call my exwife if I find my need for argumentative drama rising. I comment on this because people need to understand their history so they can live their lives peacefully and in balance.

 

[Philosothink]

fyi... the current theory is not that we evolved from apes. Apes are actually MORE evolved than we are. Our evolution has slowed to a standstill because we are possibly the most successfully evolved species ever.

currently, most evolutionary scientists accept that apes and man evolved separately, from a common, squirrel like ancestor.

 

[conway]

http://www.codeproject.com/KB/GDI/win32_Gradients/grad.jpg

That is a color gradient from red to orange to yellow. I don't think anyone would deny that it is red at the start then changes to orange then to yellow. However, where does it exactly change? You can't draw a line and say everything to the left of this is red. Well you could but it would be completely arbitrary. Same with evolution. If you looked at the family line going back millions of generations you'd see that the organism at the start wouldn't be the same species as the one at the end. To put it in our analogy the starting organism would be "red" and the ending would be "yellow". They would be undeniably different. However, at no single generational change would there be any significant difference. No parent would be a different species than its offspring.

Then how does the number of chromosomes change?

 

[DanP]

Then how does the number of chromosomes change?

http://scienceblogs.com/pharyngula/2008/04/basics_how_can_chromosome_numb.php

 

[Gokul43201]

So are you implying that even though something cannot be sensed with at least one of the five senses that it shouldn't be disregarded as false?

This has been answered once before, but I'll repeat to emphasize its importance: YES! And that's only a mild form of stating it.

Almost all fundamental science today deals with conclusions that are inferred from experiments/observations, that can not be performed simply by the five senses. Is your inability to "sense" electron transport through a nanosized transistor on a silicon chip a good reason to conclude that computers ought not to work?

 

[JerryClower]

The DNA doesn't know anything but it does recognize various things including mutations and organism can recognize when gene expression needs to change. It doesn't 'control mutations' as such however.


We've never seen the birth of a slightly different mammal? Wonder it means to have a birth defect then...
You will need to define to me what species means there are so many various definitions floating around the scientific world it's hard to keep them all straight and give a 'definitive answer' to your question.

They have offspring the same way they have their other offspring... the catch of course being they have been mutated... which has been documented MANY times so I hope you won't try to dispute this.
Yes most scientists believe that all life forms present today evolved from other life forms. (If we include that life forms are no longer being created.)
It's very easily possible. Ask more specific questions and I can give you much more specific answers.
If we go far enough back in common ancestors yes, we will go allllll the way back to ocean life forms.

I wasn't thinking about deformities. Good answer, it actually makes sense.

 

[JerryClower]

Also,


I recommend you actually read "Origin of Species". I it will clear up a lot of things for you. It can change your life for the better. And you can continue to believe in whatever magical beings you chose, because they are not exclusive of one another.

What right thinking all powerful being, would create life unable to adapt and change. Frankly, even when I was a christian, I was offended that people thought my god was too stupid to plan ahead for long term environmental changes.

Why did you assume I believed in magical beings? You know what they say about assuming, don't you?