Question about evolutionary theory?

Question

In Evolutionary theory, I am assuming similarity does not necessarily imply relationship. That would be to retarded to be believed by intelligent humans. Obviously a bat is not considered a transition species between birds and mammals. SO how in fossils do they know what is a transition species and what just acquired similar traits then dead ended. I'm thinking about archeopteryx in particular. How is it known it was an acestor to birds and not just a reptile that developed bird like flight, then dead ended, and birds came from another source.

Please no answers defending evolution. YOu are wasting your time, because I'm not attacking it. Just explain the answers nicely with terms someone with little science background can understand.

I think these things in the shower after talking with friends who are knowers, I have never attended secular education beyond English classes and math, so too many terms will lose me.

Answer 1

> I am assuming similarity does not necessarily imply relationship
Pretty good! You're absolutely right. Eyes, for example, appear to have evolved more than once. Our eyes are wonderful, and so are the eyes of cephalopods, and there are lots of similarities, but we're not particularly related to squid.

> How is it known it was an acestor to birds and not just a reptile that developed bird like flight, then dead ended, and birds came from another source
We don't know for sure. We do know that it appeared to have some birdlike qualities, and we have a bird today (the hoatzin) that appears to have some archaeopteryx-like qualities.
From the fossil record, it's impossible to tell who the ancestors are, and who the cousins-who-died-out are. Even with recent bones, such as hominid bones. We don't know which are our direct ancestors, and which are also-rans.

Answer 2

Well, since it's a constantly evolving theory, the methods they use will change over time. I know that with marine mammals (dolphins, whales, etc), they have found that flippers have a 5 finger bone structure inside. And as they locate other bones through digs, they can slowly follow a trail using a great deal of hindsight. I mean, we know what the end result is. Sometimes they start out believing one thing and then discover a bone structure that changes their mind.

A primary example would be the existence of a Brontosaurus. Initially, paleontologists found bone structures they called Brontosaurus and bone structures they labeled Apatosaurus. Later, they found a more complete skeleton and realized that the Brontosaurus and the Apatosaurus are the same creature.

In the end, the more bones and fossils we find, the more knowledge we can learn from them. But there is still a great deal of guess work involved. We can see most of the bone structure of the fossil, but if a bone is missing we may miss something.

Some is guess work, based on previous "finds" and the rest is based on the what we know of modern bones.

Answer 3

Scientists look at all the features to see the similarities. They also guess, i.e. make hypothesis. So you could be correct in your opinion that the archeopteryx dead ended. What scientists also look for are bridging species, e.g. the missing link, what you call transition species. It makes for a compelling argument if you can see how say the archeopteryx is similar to species x which is in turn similar to species y and we see how each species become closer and closer to modern day birds. But as you can see for each transition species found, there's gotta be a species in between, almost ad infinitum.

There is a reason why scientists have jobs, it's because there is still a lot more we don't know. And the more we uncover, the more questions we have.

Answer 4

The way they make these determinations isn't by just studying the fossil found, but studying all of the chararacteristics, other animal similarities/chatacteristics in that time period, as well as environmental characteristics in that time period. To simply give a one paragraph answer is impossible, for to help explain the reason it isn't concidered a "dead end" one needs the history/information which shaped the decision to call it a transitional species.

One thing that biologists and palentogists look for is homologies -- traits shared by different species. From a biology course website:
"Homologies are traits that are shared by different species because they were inherited from a common ancestor. Examples include the "universal" genetic code, vertebrate forelimbs and the vestigial whale pelvis. This site by Dr. Sally Otto gives a good overview of these and other examples, with illustrations.

"Richard Owen (1848) introduced the term homology to refer to structural similarities among organisms.

"To Owen, these similarities indicated that organisms were created following a common plan or archetype.

"That is, although each species is unique, the plans for each might share many features, just as the design plans for a Honda Civic and a Honda Prelude might be similar.

"Nevertheless, if every organism were created independently, it is unclear why there would be so many homologies among certain organisms, while so few among others.

"It is also hard to make sense of the fact that homologous structures can be inefficient or even useless.

"Why would certain cave-dwelling fish have degenerate eyes that cannot see?

"Darwin made sense of homologous structures by supplying an evolutionary explanation for them:

"A structure is similar among related organisms because those organisms have all descended from a common ancestor that had an equivalent trait. Ridley uses a specific definition of homology: "A similarity between species that is not functionally necessary." I interpret this as: "A similarity between species that exists despite several plausible alternative traits that would function equally well." "

(-from Sally Otto's website)
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Also see Steven J. Gould for much information about "dead ends" and not so dead ends. I'm not so sure he thought that there was a "direct transition" with the archaeopteryx -- though he was very much an advocate for evolution -- so reading him might give you additional food for thought, and how he understood this part of the fossil record. He has hundreds of essays, though, and I'm not sure where he directly refers to this, so it's not something to be understood in a day.

Answer 5

Remember evolution and its constructs are simply a theory--there is no theory that scientists can prove once and for all (though it is true that evolution is a theory well-verified by experiments). In addition to studying bones, there are assorted other techniques: studying the genetic basis of different organisms, analogous / homologous body parts, biochemical pathways, etc. etc. These other techniques can also generate a proposed family tree, which can be compared/contrasted with the family tree obtained by studying bones. If all techniques give the same/similar results, then scientists can believe that evolution and the family tree are probably right, but that doesn't mean that the evolutionary map scientists draw cannot be completely wrong!

Answer 6

You are discussing convergent evolution. Your question is at the heart of evolution. Before I go on to fossils, I'll discuss living creatures. Darwin did not realize that the birds he brought back from the Galapagos Islands were finches. He looked at features like beak, head and body shape to identify them. If was more subtle anatomic features that allowed identification of the birds as finches.

One of the rules of fossils is that the fossilized creature is dead. We don't know that any fossilized creature had living offspring. Statistically, very few if any fossils will have living descendants. There is no definitive way to determine relationship, but by looking at the subtle features in the shapes of the bones, a preponderance of shared independent small features suggest relatedness.

Answer 7

One method is to look at all the features. Bones, in particular, are useful because they survive well as fossils. For example, not all the little bumps and curves in an animal's hip bones are involved in flight, and so similarities and differences in those are more "believable" than similarities in bones in the wing.

Answer 8

Yours is a thoughtful question that needs a cogent answer. In particular, you need answers from others (sorry I can't help with evidence) that justify the conclusion that birds are evolutionary successors to dinosaurs (meaning any past reptiles).

Answer 9

why waste your breath on the crowd, they arent even gonna understand what you are trying to say.

I understand adaptation i understnd microevolution and survival of the fittest, but why are all the missing link species missing? Why do we not find fossils of a half reptile, half mamal? ETC?

Answer 10

one important thing to keep in mind is that it is a theory, not a law so it is constantly changing in definition