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Author Topic:   Transitional forms in existence today
Larni
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Posts: 3990
From: Liverpool
Joined: 09-16-2005
Member Rating: 7.2


Message 46 of 62 (623982)
07-15-2011 4:34 AM
Reply to: Message 45 by Portillo
07-15-2011 3:42 AM


Re: All Species are Transitional
I can understand the argument. But what Im saying is what exactly are humans going to evolve to, what kind of human or species? Natural selection creates tall, short, dark skinned, white skinned humans, but that is not evolution.

It is indeed evolution.

But in terms of what we will evolve into it is hard to say. Physically we could be like crocodiles and sharks in that we have a good body plan that has high fitness in variable environments. If this is the case there will be very little selective presssure to change (just like crocs and sharks).

If however, some global disaster knocks us back to the stone age where our physical capabilities become more relevant than our cognitive abilities I would posit that we would evolve into something more fit for the environment.


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Dr Jack
Member (Idle past 365 days)
Posts: 3507
From: Leicester, England
Joined: 07-14-2003


Message 47 of 62 (623984)
07-15-2011 4:51 AM
Reply to: Message 43 by Taq
07-15-2011 12:36 AM


Fist of pedantry
For example, the platypus lays leathery eggs and uses a cloaca like a reptile. The platypus also has fur and mammary glands like mammals do.

The Platypus is a mammal, so you either mean Theria (marsupials + placental mammals) or other mammals.


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Panda
Member (Idle past 1973 days)
Posts: 2688
From: UK
Joined: 10-04-2010


Message 48 of 62 (623988)
07-15-2011 5:41 AM
Reply to: Message 45 by Portillo
07-15-2011 3:42 AM


Re: All Species are Transitional
Portillo writes:

But what Im saying is what exactly are humans going to evolve to[?]


As soon as I finish making my time-machine, I will go into the future and find out.

Generally speaking (as a species) we will be better; we will be the same; or we will be extinct.
Do you not see that asking: "What specific direction will a non-directed process take us?" is an impossible question to answer (outside of giving vague guesses)?


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Percy
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Posts: 18842
From: New Hampshire
Joined: 12-23-2000
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Message 49 of 62 (623994)
07-15-2011 7:57 AM
Reply to: Message 45 by Portillo
07-15-2011 3:42 AM


Re: All Species are Transitional
Portillo writes:

I can understand the argument. But what Im saying is what exactly are humans going to evolve to, what kind of human or species?

It would be fascinating to discuss what selection pressures humans are and will be subjected to and what changes they might cause, but I think the most accurate answer would be, "We don't know."

Natural selection creates tall, short, dark skinned, white skinned humans, but that is not evolution.

But that *is* evolution. Expressed slightly more completely, you could say that evolution is natural selection operating upon inherent variation augmented by new mutations.

I think what you probably meant is that height and skin color by themselves are not sufficient evolution to create a new species, probably true under most circumstances. But the more two populations evolve separately the more different they become, and at some point their ability to interbreed declines to the point where we label them two different species.

--Percy


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misha
Member (Idle past 2888 days)
Posts: 69
From: Atlanta
Joined: 02-04-2010


Message 50 of 62 (624038)
07-15-2011 2:31 PM
Reply to: Message 45 by Portillo
07-15-2011 3:42 AM


Re: All Species are Transitional
Natural selection creates tall, short, dark skinned, white skinned humans, but that is not evolution.

No, you're missing it. Natural selection doesn't create tall, short, dark skinned and light skinned. Random mutation does. What natural selection will do is determine which of these traits should carry on to the next generation.

Imagine, hypothetically, that there is some great selection against people of average height. In this situation natural selection favors the short and the tall but eliminates people between say. . . 5'5" and 5'11". Eventually the entire population will either be shorter than 5'5" or taller than 5'11". The two short/tall populations probably won't interbreed much because they will produce average height humans who will be selected against.

Eventually you'll end up with two distinct populations. If enough time passes and they drift far enough away, genetically, then you will end up with two distinct species.

I understand that this is all a hypothetical. However, you must understand that:

1). we don't know the future and can not determine what variation random mutations may provide
2). we don't know the future and can not determine what types of selective pressures there may be

In order for the species to really evolve we must undergo selective pressure that affects our ability to produce offspring. At this point in human history we have enough medical knowledge that not much can affect our ability to produce offspring. Like crocodiles and sharks, we have found a niche that we fit well. There currently isn't much natural selection acting on humans, so there isn't much evolution in our species.


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jar
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Posts: 31288
From: Texas!!
Joined: 04-20-2004
Member Rating: 3.0


Message 51 of 62 (624040)
07-15-2011 2:44 PM
Reply to: Message 50 by misha
07-15-2011 2:31 PM


When will we see humans evolve?
The question about human evolution really has two most likely answers. As long as we live here on Earth it is unlikely we will ever notice evolved humans in any given population. It is possible that we might be able to see enough difference between samples separated time wise by many hundreds of thousands of years that would be large enough to classify the earlier and latter humans as different species, or if there was some major selection like the scenario you describe.

But the more likely example would be if we ever colonize other worlds. In that case we might see a relatively rapid evolution into two entirely different human species simply because each population would face quite different selective pressures and the distance are large enough to preclude ready interbreeding.


Anyone so limited that they can only spell a word one way is severely handicapped!

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Dr Adequate
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Posts: 16104
Joined: 07-20-2006


Message 52 of 62 (624043)
07-15-2011 2:57 PM
Reply to: Message 41 by Chuck77
07-15-2011 12:04 AM


Interpretation
Actually my only point was that (to me) I think most "transitional" fossils are up for interpretation aren't they? Can the fossils be labeled transitional with 100% accuracy? That was my point. Maybe they can, maybe im just ignorant of the process of establishing which fossils are in transition and which ones arent. If there all in transition how do they know where to place them? I assume it's like a puzzle that you have no picture of and trying to fit the pieces in the best you can.

An interesting question.

We can say very definitely whether B has a form intermediate between A and C. You just need a list of features of A, B and C and a pencil. Doe Archaeopteryx have feathers like a bird? Check. Does it have gastralia like a reptile? Check. Wings like a bird? Check. Teeth like a dinosaur? Check. And so forth. Interpretation doesn't come into it.

Now the existence of such forms tends to confirm the theory of evolution + common descent. The theory implies the past existence of transitional species, transitional species would have had intermediate forms, hence if the theory was right there would be intermediate forms; which there are, suggesting that the theory is correct.

Now, once we have been convinced by this and other evidence that the theory is correct, then we can interpret the intermediate forms in the light of the theory as being transitional species.

Maybe at this point I should add a note on the concept of interpretation. Creationists often talk as though this was an arbitrary or subjective act. It is not. A doctor will interpret ammonia on a patients breath as meaning that the patient's kidneys are failing; the "interpretation" that it was caused by the patient stubbing his toe is not available to the doctor, because the interpretation is constrained by the theory of physiology.

However, they are quite right to say that interpretation is theory-dependent --- all interpretation is. The doctor interprets the patient's breath in the light of physiological theories; and similarly it is in the light of the theory of evolution that we interpret intermediate forms as transitional species; a creationist would have to interpret them as something God magicked into existence for obscure reasons of his own.

But in pointing out that interpretation is theory-dependent creationists are missing the point. Two different things are going on here. To say that something is a transitional species is a theory-dependent interpretation of it. To say that something is an intermediate form is not an interpretation of it, it's just a plain factual description of it.

To summarize: on the one hand, the existence of intermediate forms (which is not a matter of interpretation) suggests the correctness of the theory; on the other hand the correctness of the theory suggests that intermediate forms should be interpreted in the light of the theory as being transitional species.

Edited by Dr Adequate, : No reason given.


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Dr Adequate
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Posts: 16104
Joined: 07-20-2006


Message 53 of 62 (624044)
07-15-2011 2:58 PM
Reply to: Message 45 by Portillo
07-15-2011 3:42 AM


Natural selection creates tall, short, dark skinned, white skinned humans, but that is not evolution.

Evolution is not defined as the set of phenomena that creationists wish to deny.


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Taq
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Joined: 03-06-2009
Member Rating: 4.6


Message 54 of 62 (624047)
07-15-2011 3:09 PM
Reply to: Message 47 by Dr Jack
07-15-2011 4:51 AM


Re: Fist of pedantry
The Platypus is a mammal, so you either mean Theria (marsupials + placental mammals) or other mammals.

Thank you for the correction, Captain Pedantry.


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Taq
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Posts: 8012
Joined: 03-06-2009
Member Rating: 4.6


Message 55 of 62 (624049)
07-15-2011 3:12 PM
Reply to: Message 45 by Portillo
07-15-2011 3:42 AM


Re: All Species are Transitional
But what Im saying is what exactly are humans going to evolve to, what kind of human or species?

No one knows, just as no one in knew that Middle English was going to transform into Modern English. No matter what, we will be transitional between our ancestors and whatever those future humans evolve into.


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hooah212002
Member (Idle past 82 days)
Posts: 3183
Joined: 08-12-2009


Message 56 of 62 (624051)
07-15-2011 3:19 PM
Reply to: Message 46 by Larni
07-15-2011 4:34 AM


Re: All Species are Transitional
If however, some global disaster knocks us back to the stone age where our physical capabilities become more relevant than our cognitive abilities I would posit that we would evolve into something more fit for the environment.

Isn't that what it would take, given that we are able to modfy our environment to suit our needs? As opposed to the environment modifying us, which is essentially what drives evolution/NS? We have the ability to grow plants that we like in places where they shouldn't grow. We have the ability to import certain animals where those animals do not naturally live. We are able to live in desert and arctic climates. I really don't see anything short of a global disaster being the means with which we could evolve, or even would evolve. We have laws and societal norms which prohibit human selection and we allow fat, stupid, ugly, pretty, fit, short, tall etc. to breed.

Of course, this is all under the assumption of first/second world areas. Could there be something like, for example, a forever undiscovered Amazonian tribe that IS effected by it's environment and doesn't have the technological capabilities as 99% of the rest of the world? Sure, but unlikely so, given how fast the rest of the world chews through resources.


"Why don't you call upon your God to strike me? Oh, I forgot it's because he's fake like Thor, so bite me" -Greydon Square

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Dr Adequate
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Posts: 16104
Joined: 07-20-2006


Message 57 of 62 (624086)
07-15-2011 7:13 PM
Reply to: Message 56 by hooah212002
07-15-2011 3:19 PM


Isn't that what it would take, given that we are able to modfy our environment to suit our needs?

To be more precise, some people are able to modify our environment to suit their wants; which is different.

But even if it was just "to suit our needs", one could still object that we did not evolve in an environment which suited our needs. For example, we need less disease. If we modified our environment so that there was none, this would remove a selective pressure which operated on our ancestors.


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Percy
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Posts: 18842
From: New Hampshire
Joined: 12-23-2000
Member Rating: 2.6


Message 58 of 62 (624121)
07-16-2011 5:38 AM
Reply to: Message 56 by hooah212002
07-15-2011 3:19 PM


Re: All Species are Transitional
hooah212002 writes:

If however, some global disaster knocks us back to the stone age where our physical capabilities become more relevant than our cognitive abilities I would posit that we would evolve into something more fit for the environment.

Isn't that what it would take, given that we are able to modfy our environment to suit our needs? As opposed to the environment modifying us, which is essentially what drives evolution/NS?

The selection pressures in environments we create for ourselves are different from the selection pressures of the natural world, but there are still selection pressures. Genetic studies seem to indicate that the human race is evolving more rapidly today than at any time in our history.

This actually makes sense and is not counterintuitive. Throughout most of our evolutionary history we had limited means of controlling our environment, and the environments of civilization are much different than anything we experienced before. We think of civilization as removing selection pressures, but what has really happened is that one set of selection pressures have been replaced by another. One example is the modern innovation of gathering into large groups called cities, necessitating the evolution of more robust defenses against hostile bacteria and viruses.

--Percy


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Dr Jack
Member (Idle past 365 days)
Posts: 3507
From: Leicester, England
Joined: 07-14-2003


Message 59 of 62 (624126)
07-16-2011 5:58 AM
Reply to: Message 52 by Dr Adequate
07-15-2011 2:57 PM


Re: Interpretation
I think it's worth noting that most transitional fossils aren't strictly speaking actually transitionals between the groups they're transitional between. We have no way of knowing whether a fossil is in the direct line of ancestry or a side branch closely related to that direct line.

The existence of the transitionals we find confirms the existence of the direct transitionals, but they are likely not to be those direct transitionals themselves.

So the real tree probably looks a bit like this:

Dinosaurs---->Bird transitional--->Birds
\
-->Archaeopteryx

rather than like this:

Dinosaurs---->Archaeopteryx--->Birds

This represents an additional layer of interpretation, but - as Dr A has explained - such interpretation is not arbitrary.


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pandion
Member (Idle past 1261 days)
Posts: 166
From: Houston
Joined: 04-06-2009


Message 60 of 62 (624284)
07-17-2011 2:31 AM
Reply to: Message 59 by Dr Jack
07-16-2011 5:58 AM


Re: Interpretation
quote:
I think it's worth noting that most transitional fossils aren't strictly speaking actually transitionals between the groups they're transitional between. We have no way of knowing whether a fossil is in the direct line of ancestry or a side branch closely related to that direct line.
The existence of the transitionals we find confirms the existence of the direct transitionals, but they are likely not to be those direct transitionals themselves.

So the real tree probably looks a bit like this:

Dinosaurs---->Bird transitional--->Birds \ -->Archaeopteryx
rather than like this:

Dinosaurs---->Archaeopteryx--->Birds
This represents an additional layer of interpretation, but - as Dr A has explained - such interpretation is not arbitrary.



Absolutely true. To continue with your example, Archaeopteryx is an example of a transitional species. But no one can state for certain a specific ancestor, nor can any descendant species be identified. Nevertheless, Archy is obviously descended from a line of maniraptoran theropods. In fact, two examples were incorrectly classified as Compsognathus, a small maniraptoran dinosaur. There are only a few differences in the skeletons. In fact, paleontologists think that Compsognathus was probably also feathered, but the feathers were not preserved since Compsognathus was terrestrial and less likely to end up at the bottom of an anaerobic lagoon. Moreover, there are only two fossil specimens that have been clasified as Compsognathus, where there are 10 specimens of Archaeopteryx plus a perfectly preserved feather.

If you take away the feathers, it takes an expert to distinguish between the dinosaur Compsognathus and the bird Archaeopteryx.


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