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Author Topic:   Transitional forms in existence today
Taq
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Joined: 03-06-2009
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Message 23 of 62 (623779)
07-13-2011 11:41 AM
Reply to: Message 1 by peter1985
07-12-2011 11:17 AM


My second reason for doubt is the very mechanism evolution uses to function- random mutation- which as many biologists acknowledge is usually, if not always, harmful.

Evolution also involves natural selection. It is a two step process where random mutation produces variation within the population and natural selection reduces the number of deleterious mutations while increasing the number of beneficial mutations.

However, if evolution is still occuring to this day, how come there are no transitional forms in existense today IE. fish with half formed limbs and such.

Your question can take on many meanings, so you may need to clarify exactly what you are looking for.

Do you mean to ask why we don't see transitional features that carried over from past evolutionary events? If so, then your question is easily answered. Let's use mammals and reptiles as an example. From the fossil record we know that modern mammals evolved from ancient reptiles. This means that modern reptiles and modern mammals share a common ancestor. Both lineages branched off at this point, and each lineage continued to evolve. In the mammal lineage, many of the branches died off. However, there is one mammalian lineage where these transitional features have been preserved: the monotremes. The most famous species of monotreme is the platypus. In this species we see a very primitive lactation system, a body temperature much cooler than other mammals, and leathery eggs like those laid by modern reptiles. As you can imagine, not all transitional features are going to be preserved in a lineage over time.

There are two things to keep in mind:

1. All lineages evolve. Reptiles did not stop evolving after mammals branched off. The same goes for all of the mammalian lineages that branched off after they evolved from reptiles.

2. Extinction happens. Lineages where transitional features can still be seen are at risk for extinction, as much as any other lineage. One of the reasons we do not see preserved transitional features is that those lineages went extinct.


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Taq
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Posts: 7774
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Member Rating: 3.8


(3)
Message 26 of 62 (623806)
07-13-2011 2:52 PM
Reply to: Message 24 by peter1985
07-13-2011 1:28 PM


peter1985,

Languages are a good analogy to use when trying to understand how evolution works. As you may know, the Romance Languages are a language group that "evolved" from Latin. Here is an idealized lineage for the Romance languages:

So you may ask why don't we hear anyone speaking a transitional language. If you went back 1,000 years you would be asking the same question even though those languages 1,000 years ago were the transitional langages between modern languages and vulgar latin. Also, the descendants of those who spoke proto-Italian, for example, are not speaking modern Italian.

If humans evolved from a common ancestor with other apes why don't we see any transitional hominids today? For the same reason that no one speaks Middle English today.

Edited by Taq, : No reason given.


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Taq
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Posts: 7774
Joined: 03-06-2009
Member Rating: 3.8


Message 29 of 62 (623820)
07-13-2011 5:24 PM
Reply to: Message 15 by Chuck77
07-13-2011 6:25 AM


The Penquin is clearly in transition. It's a seal morphing into a bird, obviously. Well, maybe a bird morphing into a seal.

What transitional mammalian features do penguins have?


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Taq
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Posts: 7774
Joined: 03-06-2009
Member Rating: 3.8


Message 40 of 62 (623938)
07-14-2011 3:25 PM
Reply to: Message 34 by Portillo
07-14-2011 4:12 AM


Re: All Species are Transitional
I dont really see how humans are transitional forms. We are fully formed creatures. Yes we may be taller or something like that, but that does not mean we will evolve into something else.

Was your father fully formed, even though he was transitional between you and your grandfather? Was Middle English a fully formed language even though it was transitional between Old English and Modern English?

I don't understand why you think that a transitional organism has to be less than fully formed.


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Taq
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Posts: 7774
Joined: 03-06-2009
Member Rating: 3.8


Message 43 of 62 (623964)
07-15-2011 12:36 AM
Reply to: Message 41 by Chuck77
07-15-2011 12:04 AM


Re: Wha?
Actually my only point was that (to me) I think most "transitional" fossils are up for interpretation aren't they?

Yes and no. It is a fact that fossils are transitionals. This is interpreted to mean that evolution occurred in the past.

Can the fossils be labeled transitional with 100% accuracy?

It is a fact that some fossils and modern species contain a mixture of features from two separate taxa. The platypus has both mammalian and reptilian features. 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. It is transitional by definition.

Biologists use the fact of transitional fossils to conclude that evolution happened in the past. What you need to keep in mind is that the transitional nature of a fossil is not what is being interpreted. Rather, scientific theories such as evolution predict which transitional fossils one should see and not see.


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Taq
Member
Posts: 7774
Joined: 03-06-2009
Member Rating: 3.8


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: 7774
Joined: 03-06-2009
Member Rating: 3.8


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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