Yes, it's another damned evolution question...

[TheStinger]

If anyone want to borrow my time machine they can go and have a look

[Lincoln]

Originally posted by Jack the Bodiless

Because creationists have never succeeded in "catching" anyone. And it's highly unlikely that they ever will, given that real scientists are MUCH better equipped to catch scientific fraud.

...Whereas bogus creationist arguments circulate for years (and are still circulating).

Elok doesn't want us to argue here.

I have read several books on the deceptive arguments of Darwinists and the presentation of "fact" for years that were spurious. Some were in school textbooks for generations. One example is Darwins moths. Another was the horse story. Creationists exposed the lies. Strive for objectivity Jack... And I have to go so see you all later...

[Jack the Bodiless]

I think you are missing my point. Why is there no drastically different animal able to fill the same niche as mammals and be just as good as it? I suppose one has to go back much further to talk about this. For example, you point out that the ear mechanism comes from fish gills. Fair enough, but why was it only fish that were able to fill the niche of turning into mammals (eventually)?

Competition with the existing occupants of the niche. For instance, mammals were basically rodentlike critters while the dinosaurs ruled: they filled the "big herbivore" and "big carnivore" niches (and the marine reptiles filled the "whale" niche too).

But given only one 'origin' we still have a similar problem: why do very early branchings not produce equally successfull mutations to end up with 2 (or more) equally successfull species, filiing a similar niche, which are completely different? We have convergent evolution, but only between recently separated species.

This happens on different continents. For instance, marsupials and placental mammals are separate branches of the evolutionary "Tree of Life": the thylacine (marsupial wolf) isn't a wolf, the koala bear isn't a bear, the opossum isn't anywhere near the lemur, and so forth.

And an armadillo isn't a tortoise either.

To give even a relatively recent example: why not have an insect which fills the same role as a grazing mammal? The only problem I see with this would be the breathing mechanism, but presumably that is not too hard to get round.

They would have to evolve lungs, ours were buoyancy bladders in fish. And then they'd have to survive predation by mammals until the next "dinosaur killer" hits (and survive that too, of course).

[Rogan Josh]

Originally posted by Jack the Bodiless
Competition with the existing occupants of the niche. For instance, mammals were basically rodentlike critters while the dinosaurs ruled: they filled the "big herbivore" and "big carnivore" niches (and the marine reptiles filled the "whale" niche too).

But many mammals compete with one another. There is no reason why one cannot have more than one species filling the same 'niche' and surviving. The question is, why do they have to be so similar?

Your later comment on 'dinosaur killer' events may be the answer to this. Perhaps there were other species filling these roles, but they were killed off by some unusual event, and have not had time to recover....

This happens on different continents. For instance, marsupials and placental mammals are separate branches of the evolutionary "Tree of Life": the thylacine (marsupial wolf) isn't a wolf, the koala bear isn't a bear, the opossum isn't anywhere near the lemur, and so forth.

And an armadillo isn't a tortoise either.

This is what I meant by convergent evolution among recent relatives. The thylacine is pretty close to a wolf on the scheme of things. But still, Australia strengthens my objections rather than weakens them. Why, for example, did the rabbit (or something similar) never evolve in Australia - it seems perfectly adapted for survival there.

They would have to evolve lungs, ours were buoyancy bladders in fish. And then they'd have to survive predation by mammals until the next "dinosaur killer" hits (and survive that too, of course).

Not really. I am sure mutations would be imaginative enough to come up with something else to let them breathe. For example, they could develop crennelated carapaces with a larger surface area allowing them to continue taking enough oxygen directly through the surface. And this can happen slowly (just like for mammals) - they can start off small and just get bigger over millions of years. The same mechanisms which allow the zebra to coexist with the antelope (or whatever) should, in principle, allow them to coexist with mammals.

Interesting thought experiment: if we were to genertically resurrect a dinosaur herbivore (eg triceritops), a la Jurrasic Park, and plonk a big enough colony of them down in a suitable environment, would the local mammalian population kill them off? Or would they kill off the local mammals? Or would both coexist and evolve?

[Jack the Bodiless]

Elok doesn't want us to argue here.

Well, that's too bad. My lack of free will makes me unable to stop.

I have read several books on the deceptive arguments of Darwinists and the presentation of "fact" for years that were spurious. Some were in school textbooks for generations. One example is Darwins moths. Another was the horse story. Creationists exposed the lies.

Are you referring to the peppered moth and Jonathan Wells?

I suggest you read Icon of Obfuscation

As for horses: no, there was no "lie" exposed by creationists. And, in my experience, creationists are suspiciously hazy on what the "lie" was supposed to be about in the first place. It's true that the "tree" of horse evolution has been adjusted as more fossils come to light, but that's just the normal progress of science.

Here's an article describing one man's quest to investigate a "lie" about horses.

[Jack the Bodiless]

Rogan:

The thylacine, being a marsupial, is about as far from a wolf as it's possible to get and still be a mammal (only the egg-laying mammals, the platypus and echidna, are more distant from wolves). Even a blue whale (or a human) is closer to a wolf than a thylacine is: these are fellow placental mammals. A clear case of convergent evolution, from a relatively distant separation. For an entirely non-mammalian "wolf", there's the Komodo dragon...

As for the rabbit: well, Australia has smallish herbivores, such as the wombat.

And a big insect would just be a crunchier and easier-to-find snack for an insectivore, it probably wouldn't survive long enough to get really big. I expect that's what kept mammals small during the dinosaur age.

[Tolls]

If you want long distance convergent evolution, how about dolphins and sharks?

Both are streamlined ocean predators that occupy similar parts of the ecologies they are in.

As for Aussie rabbits, they have a large number of small kangaroo-like marsupials that occupy the rabbit niche (of sorts)...I say "of sorts" since the niche rabbits occupy involves the creatures that surround them as well...

"Bilby, or Rabbit-eared Bandicoot, so named because of their long rabbit-like ears and their habit of building and living in long burrows. They are the only bandicoots that burrow, going down as much as 5 feet or more, and are most active at night. They use their burrows for shelter during the day.

They eat small mammals, insects and lizards. fungi, bulbs, and some fruit."

...as an example (pulled from some site about Australian beasties).

[Rogan Josh]

Originally posted by Tolls
If you want long distance convergent evolution, how about dolphins and sharks?

Both are streamlined ocean predators that occupy similar parts of the ecologies they are in.

That's a good example!

But why aren't there more examples like this? Maybe ones even furtherfrom each other on the family tree? Or even not related at all (ie. why only one 'origin')?

[Az]

The hummingbird, and the hummingmoth?

[Az]

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[Az]

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[Tolls]

I would expect them to be rare, for much the same reason that developing another "ear" type organ is unlikely...you have to overcome the existing occupant to some extent, and if you succeed in overcoming them then it is more than likely you'll supplant them in that environment.

"why only one 'origin'."

This is where we get into bacteria and their habit of absorbing DNA material from each other. Until the evolution of multi-celled organisms genetic material was pretty free flowing...throw in a couple of billion years of this and you would find it rather difficult to pinpoint the start.

Now if we're talking about multi-celled, I'd have to do some looking...

[Plan Austral]

Is is true that according to evolution the first human had to reproduce with less evolved humans?

[Neutrino]

Nice discussion going on here

One of the reasons that mammals fill many of the niches today is, as one of you mentioned, competition. Early mammals have an extremely high rate of reproduction, which means faster evolution. Also, mammals are endotherms (warm-blooded) so they can tolerate more extreme temperatures. Reptiles of any kind are very unlikely to found in arctic regions, for example.

But given only one 'origin' we still have a similar problem: why do very early branchings not produce equally successfull mutations to end up with 2 (or more) equally successfull species, filiing a similar niche, which are completely different? We have convergent evolution, but only between recently separated species.

Because when one species has become adapted to succeed in its niche, then it will evert a lot of selective pressure against the species that shares the same niche. Timing of the rise of the two species plays a big factor too in determining their eventual niches or extinction. Again like most of biology, there are lots of possible factors to consider here.

It is possible that there were more than 1 origin events. We can trace our evolutionary history among animals by looking at the development of our embryos and genes. However, when we get to the genetic level and cellular levels, things start to get fuzzy. I'm not really an expert in microbial genetics history so I won't say anything about it.
The hypothesis that I learned in class was that many organic molecules, most importantly amino acids and nucleotides, were formed around 4 bya (billion years ago). During this time, we think that the Earth was basically a large, hot stew of rocks and organic molecules, and a thin oxygen-less atmosphere. Self-replication probably arose when nucleotide polymers called RNA appeared. RNA was likely the nucleic acid used then since it's much simpler to maintain. RNA is single-stranded and linear. The modern DNA->RNA->protein sequence is far too complex for early life.
It's possible that another 'origin of life' arose and then was outcompeted and died off.

A few points I'd like to make that many non-biologists usually don't understand:

There are a few terms that may be unfamiliar to some of you. Do a search on google, I'm sure there are websites that can explain the concepts much better than I can.

1. Evolution is the change in gene frequencies over a period of time.

2. Natural selection is the differential reproductive success among a population. "Survival of the fittest" is somewhat misleading; It should be survival of the genotypes that produce the most offspring. Of course, survival is an obvious prerequisite to reproducing.

3. Many traits were not specifically evolved in response to a changing environment. This is the folly of the Adaptionist Paradigm -- that every trait was evolved for a purpose. A change in a specific gene(s) will most likely have side effects that change an individual's phenotype.

4. Evolution at the molecular level is selectively neutral [Kimura] -- mainly affected by mutation and genetic drift. These neutral mutations, if they manifest themselves as a change in phenotype, as then subject to selective pressures.

[Berzerker]

Azazel -

there is nothing surprising about it. It's not easy to reach Java from africa. You have to develope map making first.

It was easier during the ice age when the Sunda shelf - Indonesia and current islands - were all connected because sea levels were lower. It is strange that homo erectus "evolved" into anatomically modern humans ~200,000 years ago in Africa while homo erectus were still living "unevolved" in other parts of the world for another 150,000 years. I suppose one group of a species can leap forward leaving the rest behind, but what caused the leap forward? The differences between homo erectus and modern humans is quite amazing, maybe as much as between habilis and erectus. Brain size doubled from afarensis (Lucy types 3.5 mya) to erectus, and jumped by 50-100% to us in a matter of a few tens of thousands of years or less.

Rogan -

For example, why do all mammals have eyes on the front/side of their faces?

Depth perception vision is advantageous.

Wouldn't antelopes benefit from having one on the top of their head so that they could have vision when they are grazing?

Hehe, they rely on numbers so someone is usually looking. But I imagine they evolved from creatures that didn't have this problem so the hardwiring for vision didn't sprout new vision receptors to every convenient part of the body.

Predators have them on the front to give them ability to judge distances - but why not also have one behind?

Same reason they go forward faster than backward, they chase prey, not back up to it.

Hearing is another example. Why are all hearing systems basically the same? There must be thousands of ways of detecting vibrations, but only a few of them have evolved. Why?

I believe all life in the universe is similar to the life we have here. Certain designs are just better than others, so why wouldn't they appear everywhere.