Is the Earth old enough for evolution via natural selection?

[chilli]

I was reading a sci-fi book in which it is mentioned that half a million years is too short a time for the evolution of a certain kind of elbow to have occurred naturally, and it got me thinking...

Assuming an age of 4.5 billion years, is this anywhere near enough time for the complex speciation we see around us and in the fossil record to have occurred through purely naturalistic means?

[nabraxas]

depends on your definition ov 'natural' i guess.

would panspermia count?

[teonanacatl]

4.5 billion years is a long long time, and even then the earth could be and probably is still older. The hardest part is the ambigenisis, after that its easy sailing.

[foolsbreath]

I would say most definitely

It could just be the way the concept was delivered to a young and impressionable mind during my first 3 years of a science degree, but the evidence is IMO overwhelming

I mean the Galapagos finches are the ultimate example where adaptive radiation has occurred through very real changes in habitat. The time period in which natural selection is seen in this example is only a fraction of earths 4.5 billion year life span.

The Galapagos islands were turbulent in nature during the evolution of these finches with storms, temperature changes, volcanic activity and relative isolation increasing the rate at which natural selection occurred, but the earth in its entirety has been through many similar periods of large disturbance which would have sped up and slowed down the rate of natural selection at varying periods in the earths history

[MORG]

I was reading a sci-fi book in which it is mentioned that half a million years is too short a time for the evolution of a certain kind of elbow to have occurred naturally, and it got me thinking...

Assuming an age of 4.5 billion years, is this anywhere near enough time for the complex speciation we see around us and in the fossil record to have occurred through purely naturalistic means?

The evidence says yes and we've yet to find any convinving evidence to the contrary, so I'd say yes. Considering the vivid and classic examples of bacterial evolution and the moths in industrial England it's pretty clear evolution can work on large scales very quickly at times.

Sci-fi can say what it likes though. That's what the "fi" stands for.

[occidentalis]

Check out the rift lake cichlids

Hundreds of species forming in a few thousand years from just a couple in an example of very rapid radiative adaptation. Nature abhors a vacuum.

[MORG]

The Galapagos islands were turbulent in nature during the evolution of these finches with storms, temperature changes, volcanic activity and relative isolation increasing the rate at which natural selection occurred, but the earth in its entirety has been through many similar periods of large disturbance which would have sped up and slowed down the rate of natural selection at varying periods in the earths history

I think the more important factor in the radiation of these birds was competition driving niche partitioning.

Medium seed-eating birds move into an island relatively uncolonised before them and the "medium seed eater" niche is unfilled.

Birds population expands rapidly on abundance of seed. Competition for resources between conspecifics increases as population does.

Birds better able to exploit smaller or larger seeds avoid competition and hence have a reproductive advantage from others battling it out for medium seeds.

Small seed and large seed eating birds take off in numbers and genes favouring this new niche are favoured resulting in changes (eg. large bill for handling large seeds) to allow or adapt to this change in niche specialization.

By partitioning a population by niche you drive a wedge slowly between two groups. If a bird with genes good for eating large seeds mates with a bird with good genes for eating medium seeds the offspring are likely at a reproductive disadvantage in the above scenario because they're not well equipped for specialising in either large or medium seeds. Whereas if two small seed eaters mate you'll get a well equipped small seed eater at a reproductive advantage over those less specialized.

In this fashion niche partitioning can drive speciation.

It's a simplistic example but I hope I've explained it clearly.

[shruman]

The beautiful thing about evolution is that it can happen quite quickly which contradicts Darwins theory a little. The mutation of just 1 or 2 or a few genes can have a dramatic effect & if the mutation is succcessful it generaly takes off pretty fast.

Most people think about naturqal selection as being a very slow process but fossil records show it can happen quite fast.

[Ace]

evolution ... can happen quite quickly which contradicts Darwins theory a little

How does that contradict Darwin's theory? Darwin's theory simply states that natural selection creates changes in genetics of living things over time. It never stated that it was a long or short process. But I agree in that most people assume evolution takes millenia for any real changes, when this isnt the case.

[shruman]

Yeah probly a poor choice of words.

[chilli]

depends on your definition ov 'natural' i guess.

would panspermia count?

Doesn't panspermia really just address abiogenesis, not evolution? I think the author (Stephen Baxter) does go in for some kind of intelligent evolution, as he continuously talks about it choosing etc, and I don't think he's being metaphorical.

______________________________

The Galapagos islands were turbulent in nature during the evolution of these finches with storms, temperature changes, volcanic activity and relative isolation increasing the rate at which natural selection occurred, but the earth in its entirety has been through many similar periods of large disturbance which would have sped up and slowed down the rate of natural selection at varying periods in the earths history

A really good point, I hadn't considered the effect of natural catastrophes... what about varying levels of radiation, could that have had a similar effect?

______________________________

The evidence says yes and we've yet to find any convinving evidence to the contrary, so I'd say yes. Considering the vivid and classic examples of bacterial evolution and the moths in industrial England it's pretty clear evolution can work on large scales very quickly at times.

Sci-fi can say what it likes though. That's what the "fi" stands for.

The evidence, if interpreted in a naturalistic framework has to say yes, but what I am asking is if the evidence supports this framework. It is fiction of course, it is 'hard' science fiction, so the ideas are supposedly extrapolations from actual science.

______________________________

The beautiful thing about evolution is that it can happen quite quickly which contradicts Darwins theory a little. The mutation of just 1 or 2 or a few genes can have a dramatic effect & if the mutation is succcessful it generaly takes off pretty fast.

Most people think about naturqal selection as being a very slow process but fossil records show it can happen quite fast.

It's the likelihood of enough advantageous, information adding genetic mutations occurring in that time period that I can't quite get my head around... although I understand that 5 billion years is itself basically incomprehensible, and I suck at maths! Even assuming a purely naturalistic process though, spontaneous abiogenesis in even 5 billion years seems to me impossible, so even if we take as a given the existence of a living cell from God/comet/aliens or whatever, when you consider the overwhelming complexity of a single life form, and then multiply that by hundreds of millions of species wouldn't mutations have to have been succeeding pretty much continuously from the inception of life?

Your last comment has me even more confused (not difficult)... I thought natural selection by definition required long periods of time, so if the fossil record shows relatively short transitions, then wouldn't it be fair to think some other kind of mechanism was causing such rapid change? What I mean is, if phyletic gradualism is not apparently supported by the geologic record, and evolution via punctuated equilibrium works over relatively short periods, then can we even still consider it natural selection at all?

Ooh, big words.

*edit*

How does that contradict Darwin's theory? Darwin's theory simply states that natural selection creates changes in genetics of living things over time. It never stated that it was a long or short process. But I agree in that most people assume evolution takes millenia for any real changes, when this isnt the case.

Ace, is there some reason other than the apparent jumps in the fossil record that you say it isn't the case that evolution needs millennia (I would have thought longer) to create significant changes?

Edited August 31, 2007 by IllegalBrain

[Amulte]

does darwinism count as natural selection? personally i think it does to some degree.

[Auntyjack]

It's the likelihood of enough advantageous, information adding genetic mutations occurring in that time period that I can't quite get my head around...

Why can't one genetic mutation be colossal...a catalyst to the rest?

... I thought natural selection by definition required long periods of time...

I think its the definition of natural selection that is actually the problem here, from what I can gather neglecting creation when you look at natural selection (which defines one type of process with parameters) then you can't include calamities or sudden environmental changes. Maybe these play a much bigger role then natural selection?

If we group it altogether we are really just talking about the mechanisms of evolution...not natural selection.

Just my 2c

AJ

[El Barto]

i understand the part of natural selection thats gives you the long neck of a giraffe but how could the first creature to get an eye through means of natural selection

Edited August 31, 2007 by El Barto

[chilli]

does darwinism count as natural selection? personally i think it does to some degree.

I don't get it.

[chilli]

Why can't one genetic mutation be colossal...a catalyst to the rest?

I think its the definition of natural selection that is actually the problem here, from what I can gather neglecting creation when you look at natural selection (which defines one type of process with parameters) then you can't include calamities or sudden environmental changes. Maybe these play a much bigger role then natural selection?

If we group it altogether we are really just talking about the mechanisms of evolution...not natural selection.

Just my 2c

AJ

Yes, that's what I'm getting at... natural selection alone doesn't seem feasible as a sole explanation for evolution given the estimated age of the earth.

[ramon]

i understand the part of natural selection thats gives you the long neck of a giraffe but how could the first creature to get an eye through means of natural selection

Here's how some scientists think some eyes may have evolved: The simple light-sensitive spot on the skin of some ancestral creature gave it some tiny survival advantage, perhaps allowing it to evade a predator. Random changes then created a depression in the light-sensitive patch, a deepening pit that made "vision" a little sharper. At the same time, the pit's opening gradually narrowed, so light entered through a small aperture, like a pinhole camera.

Every change had to confer a survival advantage, no matter how slight. Eventually, the light-sensitive spot evolved into a retina, the layer of cells and pigment at the back of the human eye. Over time a lens formed at the front of the eye. It could have arisen as a double-layered transparent tissue containing increasing amounts of liquid that gave it the convex curvature of the human eye.

In fact, eyes corresponding to every stage in this sequence have been found in existing living species. The existence of this range of less complex light-sensitive structures supports scientists' hypotheses about how complex eyes like ours could evolve. The first animals with anything resembling an eye lived about 550 million years ago. And, according to one scientist's calculations, only 364,000 years would have been needed for a camera-like eye to evolve from a light-sensitive patch.

Cut and paste from

http://www.pbs.org/wgbh/evolution/library/01/1/l_011_01.html

[chilli]

And, according to one scientist's calculations, only 364,000 years would have been needed for a camera-like eye to evolve from a light-sensitive patch.

For this kind of complexity could develop from random mutations in such a short period of time, wouldn't there need to be almost constant mutations occurring?

[Hagakure]

when you try to picture it remember to factor in large populations of creatures.

can have simultaneous mutations occurring in different groups that are then collected together in future generations.

[devance]

There is a variable time rate.

The time around the sun would be the time mentioned.

There could be thousands of years happening on mars in a solar cycle.

The only question is that solar rays could provide enough energy to do so.

There alot of water on mars for instance but locked up very far subsurface.

So suddenly erupts one, mars planet.

Just like the bible.

Theres a notion that the moon and mars are just resources which isn't true.

Natural selection I haven't got to but (I think I got the explanation].

Maybe later, but I don't think it evolutionary selection although everybody thinks so obvious reasons.

But I am a biologist and I think I can present a explaination without peeing my pants.

Just a comment about myself .

[Ace]

Ace, is there some reason other than the apparent jumps in the fossil record that you say it isn't the case that evolution needs millennia (I would have thought longer) to create significant changes?

Evolutionary changes (anything that will help an organism adapt to a changing environment over successive generations) can happen very rapidly. Take a look at an organism with very rapid life/breeding cycles such as a fruit fly (also one of the most commonly studied for these types of research). The average ff (fruit fly) has a life cycle of about a month (sorry, cant be certain - trying to remember from my high school studies), with each generation taking, say 20 days. If environmental conditions change rapidly (say, a kid takes a couple home as pets and introduces them to a different, yet only just hospitable environment). The breeding pair may be able to produce offspring with many different traits, some of which may be better suited to the new environment (the ones better adapted for other environments will die off via natural selection). The ones that survive in this new environment will breed another generation better suited once again (though, of course there will be a couple more offspring that die cos of unsuitable genetic differences).

This has been observed in captivity with many different species (mostly those with short breeding cycles). Sure, it might take a few hundred thousand years to evolve into an organism with a new and complex sensory device (such as eyes or the electrical nerve receptors found on certain sharks (cant remember name right now)), but minor changes to a species can be the start of something huge, having a snowball effect on their environmental adaptation.

Dont forget the huge numbers of each species on earth - humans alone have some 6 billion alive at any given time (or something ridiculous), each generation differing ever so slightly from the last (look at things like height - a century ago we were about a foot shorter - who knows why we need to be taller, but it obviously plays some advantage - whether it be a reproductionary advantage, or speed, etc). It certainly doesnt take millenia for big changes - they can happen over a few decades if conditions change enough (not sure if this has been documented, but I'm sure it would have happened at some point in time - especially with new things like hydrogen bombs that can produce an area to be effected by heavy radiation levels over many decades).

Yes, that's what I'm getting at... natural selection alone doesn't seem feasible as a sole explanation for evolution given the estimated age of the earth.

Like I mentioned above, with new environmental factors that our species is able to introduce to unsuspecting populations of plants and animals (like radiation, air/water pollution, etc), it is certainly possible. In the past, it has been caused by the pollution and gasses released (not to mention the huge amounts of carbon, etc in the air) from volcanoes. There has always been things that have caused very drastic changes in species (and extinctions), such as the ice age supposedly (likely) created by a comet/asteroid collision with the earth. Very rapidly the ancestors of modern day elephants evolved from almost hairless beasts to mammoths covered in thick hair which aided their survival thru the cold years. Now mammoths have evolved back to something resembling their ancestors as modern elephants, albeit somewhat smaller. With climatic and environmental changes (including predator populations, temp changes, lack or increase of certain foods, oxygen level changes, etc, etc), species rapidly (well, not by the length of our lives, but in the big scheme of things, some thousands of years really is stuff all) change to suit and adapt so their genetics will succeed.

Adaptation really is one of the most fascinating traits life has...

[devance]

Yeah I agree with everyones opinion that genes are like a tool box and a more rapid feedback mechanism explanation is needed than simple trial and error mathematics based on a changed environment for adaption to take place as successfully and fast as is necessary.

A organism would vanish if it had to run through every lethal mutation or gene combinations that would start the process.

If one bird species was left it would change to fill all the known bird environmental niches rapidly.

A sparrow would have sparrow hawks, vultures etc.

Another way to look at it its the same with plants.

Plants are easier to see as far as fractal manifestion using the gene toolbox.

Leaves are different, the body of the plant as in cactus can be round to flat etc.

So if one type was left it could rapidly change form to diversify. Radiative speciation. Which means starts to change in all directions of the fractal gene tool box circle.

But if not the only organism left there won't a of waste time and energy in a total radiative speciation but from some sort of enviromental feed back, just go with the niche where theres no competition.

Islands are interesting.

Sometimes the lizards are big like the Komodo,

and giant land crabs.

Or sometimes small like pigmy elephants now extinct.

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