The case for Evolution.

dlofnep

I'd like to discuss the case for Evolution, and why I accept that it has been scientifically validated at every level. Evolution is often (erroneously) accused of having no evidence to support it. Clearly, it is a reactionary statement by creationists - who hear it time and time again, and feel that they can parrot it willy-nilly.

Firstly, before we delve into the evidence for evolution - I think we should state from the get go what evolution is NOT.

Evolution does not discuss the origins of life. If your argument against evolution is based on whether or not we have sufficient evidence for how life originated, then you're not arguing against Evolution I'm afraid - but against abiogenesis. (Which in itself is a fascinating topic, but not pertinent to the current topic)

Evolution is not where a dog turns into a cat, or where a crocodile turns into a duck. That is magic, and we don't believe in magic. We believe in gradual changes over long periods of time, which can eventually result in speciation.

So with evolution, over time you should find something like this:



And not something like this:



Fossil Record

When people think of Evolution, they think of fossils. While the fossil record at present is remarkable, it is not the most compelling evidence for Evolution. Or at least, not the only evidence for evolution.

We can look at the fossil record in two ways. One - is as an overall glance at how life advanced over 100's of millions of years. We see in the rock layers, the most simple forms of life in earlier rock, progressing on to fish, early amphibians, reptiles, mammals and birds and so forth..



We will never find humans before dinosaurs in the fossil record. Homo habilis will always pre-date homo sapiens in the rock timeline. And this is exactly what we would expect in a world with evolution by natural selection.

There are so many species that are well documented in the fossil record. The horse, fish to tetrapods, whale and humans are amongst these. The evidence for these transitions is clearly visible for anyone who wants to see them.

In human evolution, we see an increase in intelligence, brain-size, tool competency, and language over the course of a very long period of time all the way back to Australopithecus right up to modern day Homo Sapiens and less recently, Neanderthal. Creationists never really agree on which member of the Homo genus is man, and which is ape. What we do see however is a genus becoming less ape-like in it's traditional sense, and more human-like as time progresses. Homo erectus for example had an average brain size about 3 quarters the size of a human. So while these guys were not Einstein, they were clearly much more remarkable than the earlier Homo Habilis, who in turn was more intelligent than the even earlier Australopithecus Afarensis.

Typical arguments against the fossil record, always refer to the 'missing link'. There will always be missing links between any set of species. We are very lucky to have the record that we have. But that doesn't mean that we can't get a very solid picture with the fossil record that we have. We have a number of intermediary species, which give us more than ample information on the evolution of humans.

In the fish to tetrapod transition, we see weight bearing limbs gradually form over time along with a more tetrapod shaped head.



In the evolution of the horse, we see the animal grow in size, become more sturdier, turn from a multi-toed mammal, into a single-toed mammal, eventually into a hooved mammal.




Old traits that remain in modern species.

The idea of a flightless bird seems almost ironic. Why would a God create a bird if it could not fly? Would it not seem much more appropriate to give them the ability to fly, or to make them a mammal if they are going to spend all of their time on the ground? The real answer is that wings on flightless birds are vestiges of a time, when they could once fly. We know this based on fossil evidence and DNA analysis.

Some, like the Kiwi have wings so small that they are virtually useless. But we can see through natural selection why their wings would lose purpose. Having spent a large period of time in an area with little to no dangers on the ground - they had no need for flight. This can be of benefit to the Kiwi who can mobilise on the ground a lot easier than it's flying cousins.

A potential drawback of this however - anywhere where predators have been introduced to the areas of similar flightless birds like Kakapo, they have been hunted to almost extinction or indeed, total extinction. The problem is that evolution by natural selection doesn't happen overnight, and evolution by natural selection cannot occur quick enough to deal with a rapid threat, such as the instant introduction of a non-native predator like a cat. Once again, this is exactly what you would expect from Evolution.

Some other flightless birds, who may have lost their ability to fly - have not completely lost use in their wings. In Ostriches, we see that they have adapted their wings to serve a new purpose - balance whilst running at high speeds, for matural rituals, and for shading their young from the African heat. The penguin has obviously adapted their wings to allow them to swim.

So being able to fly is advantageous, but being more mobile on land, where there are no native predators or swimming swiftly in fish-filled waters can be even more advantageous where the habitat permits it.

We also see day's of an older time visible in other species. The whale is a great example. It curiously has a pelvis, and hind limb. If you go back slightly further to one of it's predecessor, Durudon - you see even larger limbs at 2 feet long - but yet surely spent all of it's time in the water. Even more curious is the atavisms that exist in Whales. 1 in every 500 whales is born with the remnants of it's old legs. Dormant genes which contain these features can be re-activated in an array of different species. Dormant genes from a time gone by where the Whale's ancestor had functional legs, and walked on land.



So it's clear - the evidence for evolution is compelling. Opponents of it either do not understand what the theory of Evolution states, or expect impossible evidence such as a step-by-step, fossil-by-fossil sequence of every animal that has ever existed from single-celled creatures to modern day humans. That is simply not feasible, given that fossil occurances are very rare. But it doesn't stop us from being able to build a picture - a picture that shows the important transitions.. The arrrival of early fish, the transition from lobe-finned fish to tetrapods, the evolution to reptiles, then to mammal-like reptiles, on to mammals.. The arrival of the primates is well documented, and their evolution right up to modern day homo sapiens.

So anyone who says there is no evidence for Evolution is either lying, or has not bothered to look at the evidence in an honest and rational manner. Some opponents even accept evolution within a species which they label 'micro-evolution', but 'macro-evolution' is simply micro-evolution over a much longer period of time, which results is a much greater and noticeable change.

Feel free to add any particulars to support evolution in this thread.

Gregor Samsa

Your post is perfectly valid, but I think the problem is that creationists don't accept the fossil record in the sense that you (and science) describe it: http://www.creationism.org/topbar/fossils.htm

They're starting from such a biased and irrational position (Biblical inerrancy) that no amount of evidence is going to convince them otherwise.

Sarky

Those taxonomical trees turned out to be fairly accurate once genetic analysis became advanced enough to compare DNA and protein sequences, which can compare species by the similarity of those molecules. We don't have much in the way of ancient DNA or protein sequences (Some have been discovered or inferred from some very particular fossils, actually!), but the resulting Phylogenetic trees lend further weight to the type of thing dlofnep has mentioned above. Some minor changes were necessary as it turned out that some species are slightly misclassified, but on the whole genomic analysis gives very strong evidence that we're on the right track with the concept of evolution. It helps confirm what science already suspected was very likely.

A lot of my work involves studying the similarities of secondary metabolism in different bacteria; chemical pathways that aren't necessary for a cell to survive, but which still confer some useful advantages like the ability to produce antibiotics that kill off competitors. These pathways evolved from other, more essential pathways thanks to the imperfections of genetic replication. Here's a paper that explains a fair amount about how polyketide synthase (they produce several antibiotics) genes evolved from fatty acid synthesis genes in bacteria. There are some pretty pictures that show what I mean, if you're not biochemically or microbiologically inclined.

Dades

Concise and all as your post is, dlofnep, as soon as this thread turns in a second evolution v creationism thread (and it will) it'll be locked and the crazy-talk posts deleted.

If it's consolation I can still link to it in one of the stickies for reference.

MagicMarker

This thread would go nicely with this thread.

dlofnep

MagicMarker wrote: »

This thread would go nicely with this thread.

That thread is great, if you don't mind me saying so!

sbsquarepants

OP. You're on a hididng to nothing really. Generally speaking, open minded, scientificaly thinking type people already "believe" in evolution. I say "believe" cos it's not really a belief if you can show evidence!
As for creationists, well let's call a spade a spade - they're fúcking headcases! As with any religious belief, the old mysterious ways, is their get out of jail free card. "The fossils are there to test our faith" Do you mean to test the faith that your omnipotent creator made and really shouldn't need to test, after all it's his fault if it doesn't work, does he not guarantee his work or what! Eh, well he works in mysterious ways - yes he certainly does!!
I think a big stumbling block people have with evoultion, and particularly abiogenises (i personally think the 2 are inextricably linked) is that life is some mysterious thing that needs magic to explain it. I personally think the line between living and not living things is not as clear cut as some might imagine, therfore it's a very small leap of faith, if you will, to say that life could well have evolved from non life, without any need for magic - take a look at this talk when you have a few minutes - i found it absolutely fascinating (it's not any new age crystals are alive bullshít by the way, it's real life science by a real life scientician:D)

http://www.ted.com/talks/martin_hanczyc_the_line_between_life_and_not_life.html?quote=1159

Amtmann

One thing I've always been curious about is whether the moment that one group of animals becomes distinct from another group - that is, becomes a distinct species - has ever been observed.

robindch

Amtmann wrote: »

the moment that one group of animals becomes distinct from another group - that is, becomes a distinct species - has ever been observed.

Have a read up on Ring Species:

http://en.wikipedia.org/wiki/Ring_species

dlofnep

Indeed - Ring Species is a perfect example of speciation in action. You just have to first define what a species actually is. The most widely used is the biological species concept, which basically states that a natural population of interbreeding individuals is a species.

The reasons for this was because with certain creatures like birds and insects, it's sometimes almost impossible to find any discernible differences between two different species from a visual standpoint. One study highlighted in Why Evolution is True by Jerry Coyne looked at an insect (name evades me right now) that looked identical to it's neighbouring insect, but couldn't mate with it. So at first glance, outside of the BSC - they would have been classed as the exact same species. But that's where the BSC shines.

That's essentially what you're talking about with Ring Species. The Californian salamanders are a great example. I'm sure they are on the wiki page for it.

Soul Winner

I know I'm going to get beaten up and shouted down and possibly called some names for this but the Cambrian Explosion sort of turns Darwin's Tree of life on its head doesn't it, whatever evidence there is to support Darwin's theory - and I admit there is good evidence for it - but the Cambrian Explosion has to be a major blow to it surely. If you disagree then can you explain how the Cambrian Explosion supports Darwin's theory? This is not a jab, I'd really like to know your thoughts. Now before you say that organisms that came before those found in the Cambrian period were too soft bodied to have left fossils, there have been fossils found of very soft bodied organisms in layers beneath the Cambrian, so if fossils of soft bodied creatures have been found there then why hasn't any harder bodied direct precursors to Cambrian creatures been found also? If Darwin's theory is really true then you'd expect these no?

dlofnep

You don't have to quote my OP to ask a question. It clutters the thread up. And nobody is going to beat anyone up for asking questions. So long as the question is intellectually honest, I have no problems with them.

The Cambrian explosion does nothing to impact the theory of evolution by natural selection. Firstly it's important to understand that contrary to popular creationist belief, it did not happen suddenly. It was a short period of time in the geological time-scale, but on a human time-scale, it was an immensely long period of time. In the order of millions of years.

As I stated in my original post - the fossil record isn't the only evidence for Evolution. It is not a step-by-step account of every single species that has every lived. It is snap-shots of certain periods, based on the fossils that we have found so far. The further back you go, especially at earlier periods of life - the looser the record becomes.

The reality is - we have a period of 100's of millions of years where the fossil record is quite compelling, and demonstrates the advancement of all of today's major animal groups - like fish, amphibians, reptiles, mammals and birds. Jerry Coyne probably said it best:

Jerry Coyne wrote:

many animals and plants do not show up as fossils until well after the Cambrian explosion: bony fishes and land plants first appeared around 440 million years ago, reptiles around 350 million years ago, mammals around 250 million years ago, flowering plants around 210 million years ago, and human ancestors around 5 million years ago. The staggered appearance of groups that become very different over the next 500 million years gives no support to the notion of instantaneously created species that thereafter remain largely unchanged. If this record does reflect the exertions of an intelligent designer, he was apparently dissatisfied with nearly all of his creations, repeatedly destroying them and creating a new set of species that just happened to resemble descendants of those that he had destroyed.

If you are not convinced by my original post that it gives a solid argument in favour of Evolution being a scientific face, then perhaps you'd care to critique it.

Soul Winner

dlofnep wrote: »

You don't have to quote my OP to ask a question. It clutters the thread up.

I just deleted the quoted OP.

dlofnep wrote: »

And nobody is going to beat anyone up for asking questions. So long as the question is intellectually honest, I have no problems with them.

OK

dlofnep wrote: »

The Cambrian explosion does nothing to impact the theory of evolution by natural selection. Firstly it's important to understand that contrary to popular creationist belief, it did not happen suddenly. It was a short period of time in the geological time-scale, but on a human time-scale, it was an immensely long period of time. In the order of millions of years.

But according to standard Darwinian principles the changes take place over vast time scales. Is a few hundred million years enough time to get from basic microbial life to the plethora of significantly more advanced organisms found in the Cambrian? If it happened that way then the changes are not really that slow at all. Under the theory you'd expect fewer forms and in a significantly more privative state than are actually found.

dlofnep wrote: »

As I stated in my original post - the fossil record isn't the only evidence for Evolution. It is not a step-by-step account of every single species that has every lived. It is snap-shots of certain periods, based on the fossils that we have found so far. The further back you go, especially at earlier periods of life - the looser the record becomes.

Yeah I get that.

dlofnep wrote: »

If you are not convinced by my original post that it gives a solid argument in favour of Evolution being a scientific face, then perhaps you'd care to critique it.

Like I said I'm not saying that it hasn't got good evidence to support it, it has, plus I don't have the time - or possibly the adequate know how - to adequately critique your OP, but lets stick to Cambrian Explosion for now. The Cambrian Explosion is at best, evidence that the process works much faster than is predicted by the theory or at worst counts against the theory completely. Can you explain the speed differential at this early epoch compared to other epochs?

Amtmann

Amtmann wrote: »

One thing I've always been curious about is whether the moment that one group of animals becomes distinct from another group - that is, becomes a distinct species - has ever been observed.

That's not necessarily true.

First of all, the statement is anthropocentric, though admittedly for the good reason that as far as we know humans are the only species on Earth with the capacity to make such an observation and to understand its significance.

Secondly, it is only quite recently in human development that we have acquired the knowledge and the technology to make it possible to observe, record and analyse the significance of a "speciation event". For most of the history of the human species, people might have observed "a moment" when a distinct species occurs - but would not have been able to record and analyse this, or even to understand what they were observing.

Species last a blink of an eye in terms of the age of the Earth, but they last a very long time in terms of human lifespan. Since the dawn of "urban" human civilisation about 11,000 years ago, there have probably been a relatively small number of "speciation events". Unless humans happened to be in the right place at the right time, how would they observe one of those events? And if they did, how could they understand what they were seeing, given their lack of scientific knowledge?

And in any case 11,000 years is too generous a timescale to consider. For most of that, humans didn't really have a clue how species came about, and certainly lacked the scientific know-how and the technology to test and research the subject. We've only had a grasp of the concept of evolution by natural selection for about 150 years, and only had a grasp of what DNA is for about 60 years. That is an absurdly short timescale by reference to the age of the Earth or the lifespan of a species. If you were to pick any 60 year time slot in Earth's history and travel back in time to study in it, you would have to be very lucky indeed to spot and record a "speciation event".

One big problem for anyone trying to get their heads round evolution - and it is a problem with which creationists are terribly afflicted - is that the timescales involved are mind-bogglingly huge. Humans can just about get a feel for a time period of 70 to 100 years, but beyond that we really find it hard to conceptualise the effects of the passing of time. And the timescales involved in evolution are colossal. Thus, one might consider anatomical features such as shells or bones to be too complicated to evolve - until we realise that living things were around for almost 3,000 million years before this development took place.

A good parallel is the area of geology and plate tectonics. Plates (and the land on top of them) move really slowly, typically about 2 or 3 centimetres a year. You wouldn't notice that (though it can be measured), but over a long time it adds up to a lot. It's 65 million years since the extinction of the dinosaurs. In that time, a bit of land will have moved anywhere between 1,300 and 2,000 kilometres across the surface of the Earth.


And that's before we get into any debate about what exactly constitutes a species. :eek:

Galvasean

Soul Winner wrote: »

But according to standard Darwinian principles the changes take place over vast time scales. Is a few hundred million years enough time to get from basic microbial life to the plethora of significantly more advanced organisms found in the Cambrian? If it happened that way then the changes are not really that slow at all. Under the theory you'd expect fewer forms and in a significantly more privative state than are actually found.

There was actually a lot more than basic microbial forms plodding around before the Cambrian. There have been many clearly defined members of what is now called 'the animal kingdom' found living long before the 'explosion'.
I also appears that diversification during the 'explosion' was not particularly quick either.
There's a good write up on it here (although some terms are bit techy, but should be gooleable enough - although I'm sure some regular posters will be happy to help out):
http://en.wikipedia.org/wiki/Cambrian_explosion#How_real_was_the_explosion.3F

To put it in context, the 'explosion' is usually measured as having lasted between 80 and 100 million years. Consider the giant dinosaurs of the Cretaceous were wiped out in a mass extinction roughly 65 million years ago. At that time the largest/most complex mammals were no bigger than rats. In only 65 million years said mammals have diversified into elephants, humans and even whales that dwarf the largest of dinosaurs.
Surely the advances evolution made during the 'Cambrian Explosion' don't seem all that spectacular when compared to that which has occurred in the last 65 million years?

dlofnep

Soul Winner wrote: »

But according to standard Darwinian principles the changes take place over vast time scales.

Actually it doesn't. Change can be gradual over long periods of time, or it can be relatively quick over shorter periods of time. (We're talking the geological time scale). One theory discussing this is the theory of Punctuated equilibrium. Essentially it states that a species can have very little change over long periods of time, but when the environment requires adaptation - it can happen a lot quicker.

Soul Winner wrote: »

Is a few hundred million years enough time to get from basic microbial life to the plethora of significantly more advanced organisms found in the Cambrian? If it happened that way then the changes are not really that slow at all. Under the theory you'd expect fewer forms and in a significantly more privative state than are actually found.

I've already stated that the fossil record is imperfect, and the fossilization process is a very rare event. There are a number of theories as to why life evolved at a much faster rate during the Cambrian explosion.

Let's take a hypothetical scenario. Suppose we have a species. We'll call him Irelanditicus. Irelanditicus spends 10 million years living in the forests of Sahara Africa. It is a successful animal, and because it is successful - it sees relatively little change, if any over those 10 million years.

Then suddenly (over the course of 250,000 years) - the climate dries up, and the forest retreats, leaving grassy plains behind it. The Irelanditicus goes from have a varied diet of fruit, insects and leaves - and is forced now to live on a much plainer diet of grass.

In order to be successful at this - natural selection might favour those who are smaller, have better jaws for chewing the grass, wider teeth, a larger appendix, etc.. So after another 250,000 years - the Irelanditicus sees drastic change and becomes an entirely new species. But looking back at the fossil record, all we see is a species which appears stable over 10 million years, and then suddenly becomes drastically different over 250,000 years. It's only later when we analyse the plant-life and acknowledge the receding of the forests that we understand the pressures that forced this evolution.

So - Evolution doesn't state that all species will evolve at the same rate, or that there is a set period of time that a species must have before it evolves. It is completely arbitrary and solely dependant on a number of conditions and environmental pressures.

I hope this clears it up for you.

Soul Winner

Soul Winner wrote: »

The Cambrian Explosion is at best, evidence that the process works much faster than is predicted by the theory or at worst counts against the theory completely. Can you explain the speed differential at this early epoch compared to other epochs?

What speed differential? Originally, it was thought that the speed of evolution and diversification of species was sharply different to other periods, but more modern statistical analysis demonstrates that it wasn't sharply different to what came afterwards. The rate of evolution of new animal species was certainly faster than what went before - but that is to be expected and is consistent with natural selection theory.

What does stand out about the Cambrian Explosion is the surge in species disparity (different shapes, sizes, ecosystem niches and so on). The fact that this was greater than in pre-Cambrian times is (again) to be expected. What makes for an intriguing question is why this disparity levelled off rather than continuing to expand exponentially. However, more recent research suggests that in fact the "surge in disparity" took place over a longer period than the Cambrian Explosion. While the question is intriguing, it hardly amounts to "counting against the theory". It just means that more work has to be done to test the hypotheses and come up with answers.

dlofnep

dlofnep wrote: »

So - Evolution doesn't state that all species will evolve at the same rate, or that there is a set period of time that a species must have before it evolves. It is completely arbitrary and solely dependant on a number of conditions and environmental pressures.

And in fairness, my point about long timescales might on the face of it seem to contradict the above, but it doesn't. My point is not about how long any specific "bit of evolution" should take to happen - it's about how long a human would have to be around so that a sufficient amount of evolution would take place to make a difference to what they would see in the landscape around them.

dlofnep

Deleted User wrote: »

And in fairness, my point about long timescales might on the face of it seem to contradict the above, but it doesn't. My point is not about how long any specific "bit of evolution" should take to happen - it's about how long a human would have to be around so that a sufficient amount of evolution would take place to make a difference to what they would see in the landscape around them.

Well, we can witness over a human life in a species that has a very short generational life - like bacteria etc.. But I think what opponents to Evolution want is someone more in their face, like the speciation of a mammal. It's an unrealistic expectation, driven by either ignorance or by intellectual dishonesty.

robindch

Soul Winner wrote: »

I know I'm going to get beaten up and shouted down and possibly called some names for this but the Cambrian Explosion sort of turns Darwin's Tree of life on its head doesn't it

No.

dlofnep

dlofnep wrote: »

Well, we can witness over a human life in a species that has a very short generational life - like bacteria etc.. But I think what opponents to Evolution want is someone more in their face, like the speciation of a mammal. It's an unrealistic expectation, driven by either ignorance or by intellectual dishonesty.

I think the intellectually dishonest don't really have the unrealistic expectation - but they're smart enough to know how to play to the gallery of the ignorant.

Ironically, looking at species the way we do is both a help and a hindrance.

It helps people to understand the notion that species developed and that evolution by natural selection makes sense as a mechanism for this to happen.

It hinders by creating illusory demands and expectations; a new species appearing before our eyes, a crocodile that turns into a duck, or a never-ending search for missing links. :rolleyes:

We're all missing links, so to speak.

strobe

MagicMarker wrote: »

This thread would go nicely with this thread.

Hmm, I'm getting a warning from trying to click that link, apparently it 'contains content from psdtutorials.org, a site known to distribute malware[...]'.

Soul Winner

strobe wrote: »

Hmm, I'm getting a warning from trying to click that link, apparently it 'contains content from psdtutorials.org, a site known to distribute malware[...]'.

Yep me too.

Galvasean

Weird I visited it the other day (It's the Short History Of Almost Everything thread). Afraid to now though

Soul Winner

Galvasean wrote: »

Weird I visited it the other day (It's the Short History Of Almost Everything thread). Afraid to now though

Have your read the book? One of my favs (except for the chapter on botany), must read it again sometime soon.

Cossax

I was there the other day and it was fine. Having a look now, the only PSD reference I see in the source is Daftendirekt's Stop SOPA Ireland sig.

strobe

Cossax wrote: »

I was there the other day and it was fine. Having a look now, the only PSD reference I see in the source is Daftendirekt's Stop SOPA Ireland sig.

The warning appears to be gone now in anyway... Not sure what the deal was...

Oh Jesus, what if the malware viruses have evolved to circumnavigate googles warning systems!?

Annnnddd.... thread back on topic.

RichieC

I love this forum.

If I might be so bold as to make a suggestion for this thread, though. I think it would better serve if it was confined to evidence for evolution rather than a debate as it will be quickly swamped by folks like J C and the thread will devolve into a ****fest.

Thanks.

Galvasean

I'm not sure. Having a place where people can ask honest questions about evolution (like SoulWinner did) can only be a good thing IMO. This thread is a great place to learn. Unlike the 'other' thread where one must filter through mounds of waffle to find anything worthwhile.
Perhaps arrange to move any CSFI related crap to the 'other' thread.

dlofnep

Like I said - I've no problems with questions, so long as they are intellectually honest. Something certain posters are not capable of doing. Perhaps if a moderator could remove all posters that are not presenting evidence for evolution, or discussing evolution (including this post) - It will make the thread a lot easier to read.

Dades

dlofnep wrote: »

Like I said - I've no problems with questions, so long as they are intellectually honest. Something certain posters are not capable of doing. Perhaps if a moderator could remove all posters that are not presenting evidence for evolution, or discussing evolution (including this post) - It will make the thread a lot easier to read.

As alluded to here, undercover-creationists are not welcome. And rest assured they are pretty easy to spot.

Will try to avoid lockage and just use jackbooted censorship instead.

dlofnep

Also worth looking at is why there is a lack of native species on Oceanic Islands. It's important to learn the distinction between Continental Islands and Oceanic Islands, to understand why this supports Evolution.

Oceanic Islands are relatively new Islands, that sprung up (typically from volcanic activity) and were never a part of a continent. Continental islands would have been part of a continent at one point in time, but have since become detached through a variety of means (Rising seas, ice caps melting, etc). They still rest on the continental shelf however.

When looking at the life that exists on the different island types, biologists noticed that the only life that existed in Oceanic islands, were species that had the ability to migrate there (swim, fly, etc..) and originated from near-by land-masses.. Continental islands however, have a vast array of native species, because they have existed for a much longer period of time - and such, have had the the time-span required to accommodate for mass speciation by natural selection.

Now that's not to say that Evolution does not occur on Oceanic islands, but that when comparing two islands of comparable size, habitat and climate - the one with a continental origin varies drastically than the Oceanic island.

Question for the theist: If God created the Earth - then why would he create two islands with similar climates, size and habitats - but provide a much wider array of species on the continental island?

dlofnep

Evolution over very short periods of time.

While speciation can take a considerable length of time, up to millions of years - Evolution itself of a species can be visible within a dozen or two generations. One experiment performed by John Endler examined the role that spots play in the survival of guppies.

The experiment setup artifical ponds for the Guppies, with different types and coarseness of gravel. Each pond had a predatory fish present, to pressure selection of the fish.



Over the course of 15 generations, the fish in each pond adapted their spots to reflect the gravel in their respective ponds. While the Guppies that were put in each pond were originally the exact same, by the time 15 generations passed - their appearance was greatly altered. The results were clear cut proof of evolution in action.



Good outline of the experiment here for anyone who wants a read: http://evolution.berkeley.edu/evosite/evo101/IVB1bInthelab.shtml

Galvasean

What I found most interesting in the guppy experiment is that ironically in the absence of a predator the guppies who stood out from their surroundings (ie: the ones with bad camouflage) were sexually selected and went on to dominate.

Oranage2

There's no doubt species evolve and even take a look at our own species and how the different races have different variations.


But i don't quite get how we evolved from chimps. Chimps are a thriving species and so are humans but how come there aren't and species inbetween or even any evidence of the 'missing link'. Maybe somebody could point me in the right direction, very interesting op.

dlofnep

Oranage2 wrote: »

There's no doubt species evolve and even take a look at our own species and how the different races have different variations.


But i don't quite get how we evolved from chimps. Chimps are a thriving species and so are humans but how come there aren't and species inbetween or even any evidence of the 'missing link'. Maybe somebody could point me in the right direction, very interesting op.

That's because we didn't evolve from chimps. Humans and chimps share a common ancestor which lived about 7 million years ago.

RichieC

Oranage2 wrote: »

There's no doubt species evolve and even take a look at our own species and how the different races have different variations.

dlofnep

As for the missing link canard, there are mass amounts of 'links' going back through a number of different species. The Homo genus alone has about a dozen members. Then we have a handful more within the Australopithecus family.

The 'missing link' might have been a valid question when Darwin was alive, but since then we have found 1000's of fossils documenting the evolution of apes, including the homo genus.

Galvasean

Oranage2 wrote: »

There's no doubt species evolve and even take a look at our own species and how the different races have different variations.


But i don't quite get how we evolved from chimps. Chimps are a thriving species and so are humans but how come there aren't and species inbetween or even any evidence of the 'missing link'. Maybe somebody could point me in the right direction, very interesting op.

For starters it's worth noting that humans did not evolve from chimps and no one in evolutionary biology claims this. It is however a somewhat common misconception, in that when people hear that 'humans evolved from' they assume it means 'humans evolved from currently living apes', which is incorrect. The last common ancestor that humans and chimps share is believed to have lived some 7 million years ago. You can delve more into it here:
http://en.wikipedia.org/wiki/Chimpanzee-human_last_common_ancestor
and also here:
http://en.wikipedia.org/wiki/Human_evolution#Divergence_of_the_human_lineage_from_other_Great_Apes

The term 'missing link' is also somewhat misleading and is generally not used among the scientific community, but unfortunately very popular among pop-science magazines and tabloids for the sake of sensationalism and selling magazines/newspapers.
There have been several of these so called 'missing link' apes found which show a transition from more primitive ape to man over time.
Ardipithecus, which lived over 4 million years ago, appears to be one such ape:
http://en.wikipedia.org/wiki/Ardipithecus
Australopithecus, which lived at a later date (around 3 million years ago) shows more human features than 'Ardi':
http://en.wikipedia.org/wiki/Australopithecus#Evolutionary_role
Without going into too much detail you can see branches of prehistoric apes becoming more human like the closer we come to modern times.

I would strongly recommend having a read through this page:
http://en.wikipedia.org/wiki/Human_evolution#
and then returning here with any follow up questions (as some of the links I've posted can be a bit on the technical side).

darjeeling

Oranage2 wrote: »

But i don't quite get how we evolved from chimps.

We didn't. Chimps are like very distant cousins. We didn't evolve from our cousins, but we share a common ancestor with them.

Oranage2 wrote: »

Chimps are a thriving species and so are humans but how come there aren't and species inbetween

This is like asking why there is no language in between Italian and Spanish, given that they have a common root. Why should there be?

Oranage2 wrote: »

or even any evidence of the 'missing link'.

What precisely are you thinking of when you use the phrase 'the missing link'? There are plenty of fossils of hominins that have a number of ancestral characteristics shared with the other great apes, and other derived characteristics seen today only in humans. This is consistent with what we would expect if humans had evolved from a common ancestor shared with the other great apes.

Add comparison of genome sequences into the mix (and we now have genomes for all the great apes) and the evolutionary closeness between human, chimp, gorilla and orang-utan is clear. The family tree we obtain is unambiguous, and replicates what we see from anatomical measurements.

sephir0th

Oranage2 wrote: »

Chimps are a thriving species and so are humans but how come there aren't and species inbetween.

This is quite an interesting question if you look at it in terms of what is alive today. Galvasean has pointed out evidence for transitional species from the common ancestor to modern humans. Obviously, all these species are now extinct.

I guess the tangential question I would pose is, presumably some of these species had adapted to a degree of intelligence higher than the modern chimp, was it just a case that the selection pressures were harder on the human line than the chimp line?

Galvasean

sephir0th wrote: »

This is quite an interesting question if you look at it in terms of what is alive today. Galvasean has pointed out evidence for transitional species from the common ancestor to modern humans. Obviously, all these species are now extinct.

I guess the tangential question I would pose is, presumably some of these species had adapted to a degree of intelligence higher than the modern chimp, was it just a case that the selection pressures were harder on the human line than the chimp line?

Intelligence isn't the be all and end all of evolution though. Depending on the ecological niche sometimes it is better to be agile, strong, what have you than very intelligent. Chimps live in places full of trees and have evolved great agility to take advantage of such.
Hypothetical example:
Chimp 1 is more agile but not as clever as chimp 2. One day Chimp 2's lack of agility results in him falling from a tree and dying, failing to send on his genes to the next generation. His intelligent genes are lost to the gene pool while Chimp 1's agile genes remain.
I know it's a very basic analogy, but I hope it answers your question (that is, if I am reading your question correctly in the first place).

darjeeling

sephir0th wrote: »

This is quite an interesting question if you look at it in terms of what is alive today. Galvasean has pointed out evidence for transitional species from the common ancestor to modern humans. Obviously, all these species are now extinct.

I guess the tangential question I would pose is, presumably some of these species had adapted to a degree of intelligence higher than the modern chimp, was it just a case that the selection pressures were harder on the human line than the chimp line?

Selection pressures were different, I think we can say. Proto-chimps seem to have remained in more forested environments, whereas proto-humans moved into more savannah-like environments. Incidentally, this difference in habitat helps explain why chimp ancestor fossils are so scarce (mostly we just have fossil teeth).

Changes in diet may help account for the increase in human brain size and complexity too. Actually I was just reading this in the Guardian this morning:
How many neurons make a human brain?
From the article, our brains have around three times the number of neurons seen in a gorilla. They also use a remarkably large amount of our energy intake (20-25% is quoted), so it may have taken a switch in the foods our ancestors were eating, and the way they prepared them, to allow for the dramatic expansion in the brain.

Galvasean

darjeeling wrote: »

Changes in diet may help account for the increase in human brain size and complexity too. Actually I was just reading this in the Guardian this morning:
How many neurons make a human brain?
From the article, our brains have around three times the number of neurons seen in a gorilla. They also use a remarkably large amount of our energy intake (20-25% is quoted), so it may have taken a switch in the foods our ancestors were eating, and the way they prepared them, to allow for the dramatic expansion in the brain.

If I remember correctly the move to savannahs led to a more protein based diet (meat, nuts etc.) which is very helpful for producing big brains. Apes in forests rely more heavily on abundant fruit and vegetation.

RichieC

Galvasean wrote: »

If I remember correctly the move to savannahs led to a more protein based diet (meat, nuts etc.) which is very helpful for producing big brains. Apes in forests rely more heavily on abundant fruit and vegetation.

Yea, in a documentary I watched last night they cited a change to shellfish as catalyst for even further frontal lobe development.

sephir0th

Galvasean wrote: »

Intelligence isn't the be all and end all of evolution though.

I understand that increased intelligence isn't necessarily the marker of a successful adaptation. But a chimp with all the flexibility of another chimp except with some extra intelligence, I thought would have been favoured. Perhaps the selection pressure, as you say, in forested environments just wasn't there along with the correct food protein sources.

darjeeling wrote: »

Changes in diet may help account for the increase in human brain size and complexity too. Actually I was just reading this in the Guardian this morning:

That would explain a lot. Presumably both lines would have adapted towards larger brains at some point right? A larger brain doesn't necessarily have to come at a cost to flexibility etc. or does it? Food sources may explain it.

Solair

You're basically evolutionary cousins with any living, modern species of animal (and very very distant cousin to insects and plants etc)

we all evolved from ancient, organisms.

in fact, you've even got DNA in common with a banana, or even bacteria never mind apes if you go back to absolutely the start of evolution.

Oranage2

darjeeling wrote: »

What precisely are you thinking of when you use the phrase 'the missing link'?

To be honest, I was expecting cute little monkey men running around.

Galvasean wrote: »

For starters it's worth noting that humans did not evolve from chimps and no one in evolutionary biology claims this. It is however a somewhat common misconception, in that when people hear that 'humans evolved from' they assume it means 'humans evolved from currently living apes', which is incorrect. The last common ancestor that humans and chimps share is believed to have lived some 7 million years ago. You can delve more into it here:
http://en.wikipedia.org/wiki/Chimpanzee-human_last_common_ancestor
and also here:
http://en.wikipedia.org/wiki/Human_evolution#Divergence_of_the_human_lineage_from_other_Great_Apes

The term 'missing link' is also somewhat misleading and is generally not used among the scientific community, but unfortunately very popular among pop-science magazines and tabloids for the sake of sensationalism and selling magazines/newspapers.
There have been several of these so called 'missing link' apes found which show a transition from more primitive ape to man over time.
Ardipithecus, which lived over 4 million years ago, appears to be one such ape:
http://en.wikipedia.org/wiki/Ardipithecus
Australopithecus, which lived at a later date (around 3 million years ago) shows more human features than 'Ardi':
http://en.wikipedia.org/wiki/Australopithecus#Evolutionary_role
Without going into too much detail you can see branches of prehistoric apes becoming more human like the closer we come to modern times.

I would strongly recommend having a read through this page:
http://en.wikipedia.org/wiki/Human_evolution#
and then returning here with any follow up questions (as some of the links I've posted can be a bit on the technical side).

Interesting indeed, though I'm not convinced we or the other species have all evolved from a single celled organism. After doing a bit of looking up it seems that there's not much fossil evidence that we have evolved from any sort of chimp man. Even the great pioneer of evolution Charles Darwin doubts his theory

"Lastly, looking not to any one time, but to all time, if my theory be true, numberless intermediate varieties, linking closely together all the species of the same group, must assuredly have existed. But, as by this theory, innumerable transitional forms must have existed, why do we not find them embedded in countless numbers in the crust of the earth?"

Again I do believe that species like humans can evolve through genetic selection, I just dont think there's enough evidence to believe we all evolved from the same ancient organisms.

oldrnwisr

Oranage2 wrote: »

Interesting indeed, though I'm not convinced we or the other species have all evolved from a single celled organism. After doing a bit of looking up it seems that there's not much fossil evidence that we have evolved from any sort of chimp man.

We don't need fossil records to provide evidence for common descent. There are many overlapping fields which biologists use to provide an overall picture of how evolution has occurred.

Genetics is one of those fields. Some time ago, someone noticed that while we only have 23 chromosomes our cousins in the primate family have 24. So if we share a common descent with other primates, then at some point, two of the ancestral ape chromosomes must have become fused together. This is what we find to be the case.



We were able to verify this in several different ways. Firstly, the banding pattern on human chromosome 2 matches that on chimp chromosomes 12 and 13 when lined up. Secondly, the end of a chromosome is marked by a sequence called the telomere. When we look at the telomeres of the chimp chromosomes we find that the same sequences are found in the centre of human chromosome 2, indicating fusion. If you want I can post some of the research that demonstrates this in more detail, or alternatively I can post some of the other genetic evidence for common descent such as endogenuous retroviruses (ERVs) or bornavirus.

Oranage2 wrote: »

Even the great pioneer of evolution Charles Darwin doubts his theory

Please don't do that. We were having such a nice discussion on evolution. I swear if I see a quote about the eye I'm going to go postal!

sephir0th

Oranage2 wrote: »

I just dont think there's enough evidence to believe we all evolved from the same ancient organisms.

How hard have you looked?

Here's a start:
http://www.talkorigins.org/faqs/comdesc/

Sarky

Innumerable transitional fossils HAVE been found though. Fossils are pretty rare due to the circumstances required for their creation. Taking that into account we've discovered a huge number of them, easily more than enough to cement evolution as the way things happened.

Darwin was perfectly right to be skeptical at the time, but a shedload of evidence has been found since then. If he were alive today he'd agree that he was right about evolution.