Why Can't Evolution Go Backwards?

I think back to my textbooks as a young child which never referred to evolution as a theory. The diagrams all showed a progression from an ape-like creature to a man-like creature and then, finally our 'civilised' ancestors.

My point is why is there always a progression from less complex to more complex and from less sophisticated to more sophisticated?

Over the course of many millions of years with a Blind Watchmaker (Dawkins) why can't species de-evolve to other forms. For example why didn't the man-like apes de-evolve back into apes, pigs, donkeys or fish?

There should be no reason why de-evolution couldn't have occurred if climatic, behavioural, genetic and other biotic and abiotic factors favoured a backwards evolutionary step. Yet...I have never read a scientific theory that allow evolution in both directions. I wonder why?

Depends how you define complexity. How do we measure it?

Is a dolphin less complex than its closest ancestor? Is a snake less complex than a lizard? Is an ape less complex than a monkey? Is a blind shrimp less complex than a sighted shrimp? Is a human less complex than lower mammal?

In each case we could view some degree of complexity ---> simplicity (e.g., limb to fin; tail to no-tail; legs to legless; sight to blind; cellulose-digesting caecum to human appendix).

Perhaps because climatic, behavioural, genetic and other biotic and abiotic factors didn't favor a backwards evolutionary step. However, we've only been studying this stuff for a relatively short period of history We can't really observe long-term changes because we haven't been looking long enough. Maybe we have deevolved several times along the way and just don't know it.

Evolution doesn’t go backwards for the same reason it doesn’t go forwards.
It doesn’t exist. The theory of evolution has not, can not, and will not, ever be proven.

I think of it like this, if there was a beginning (big bang) then there should be an end, right? Everything which has a starting point must have a finishing point no?

The universe evolved from what I can only imagine was pure energy to there being gases to there being stars etc etc etc. Everything became more complex as time passed. Will the universe one day start to collapse in on itself and thus start to de-evolve? I believe there was a big bang but I don’t believe that was the start of everything, I believe it was the beginning of this particular universe yes, but not the beginning of the bigger picture which science has only fairly recently started to touch up on (ie string theory and multiple dimensions).

My 2 pence.

ps. Just food for thought, in Newtonian law isn’t it stated that for every action there is an equal and opposite reaction? Is evolution an action? if so, is it excluded from the rule?

edited spelling mistake =p

[edit on 27-11-2007 by rapturas]

things can't "devolve"
any change to an organism is an evolution, whether or not it resembles a return to a previous form.

example: whales started out as land animals that went back to being aquatic.
it's going back to a much much much earlier form, but still evolution.

...and why the hell does the word "theory" matter?

www.abovetopsecret.com...

watch the damn videos...

Some believers of De-evolution

Well, some might point to land mammals who returned to the sea and their limbs became vestigial.

That would include Cetaceans and Pinnipeds, who 'devolved' from land animals and went back into the sea, presumably "allowing them" to exploit this very lucrative ecological niche.

www.ratical.org...
Somewhere around 50 million years ago, just before India struck Asia, it pushed the seafloor up, forming a warm shallow sea called Tethys that teemed with plankton life and lured some early wolf-like creatures back to the aquatic life. This is the apparent origin of the sea mammals we call cetaceans, which include whales and dolphins. First the wolf-like creature reverted to a sort of hairy crocodile amphibian stage, then they took seriously to the seas, giving up fur and feet for smooth skins and flippers. Pinnipeds -- `fin-feet' -- also became aquatic mammals, such as sea lions and walruses.

In addition you might say also cite the example of large birds who have largely lost their ability to fly (except for some short hops) and became land dwellers, like the Ostrich and the Emu.

The form that they seem to imitate is the Raptor, which was a highly successful species and made a superb predator. So there again you have some advantage in exploiting that niche by getting larger and developing the ability to run fast.


[edit on 27-11-2007 by Badge01]

I believe that we as humans made this world more complex, I mean look at it from this angle; we went to the moon, trying to go to mars, cloning people, looking for life 5 miles below sea level, and still people are trying to tell us that "this world is complicated" i say otherwise.

And as far as this whole Evolution theory goes, i don’t believe that one bit, just because there is no scientific proof in the leap from man like looking creature and today’s human.

I find the point about cetacean origin fascinating. Is there fossil or other evidence to show this example of change?

I would define complexity of function related by the different number of functional tissues or organs in an organism. In that case, melatonin's arguments hold some water. However, I am more interested in the development of humans and, in particular human consciousness.

Even if we look at the orthologs of blood clotting factors in pufferfish and humans. we find a similarity of protein sequence that approximates to anbout 45%. To a neo Darwinist, this is proof of a lack of irreducible complexity because 'fish are our ancestors and therefore the blood clotting process has increased in complexity inside us through progressive evolution'.

However, why couldn't an ape like creature de-evolve into a puffer fish? Why can't apes have developed from human like creatures existing hundreds of million years ago - unlikely as it seems!

However, why couldn't an ape like creature de-evolve into a puffer fish

Well, I guess it could happen. I don't think you would find over millions of years a dolphin developing into a puffer fish, but a similar species? Why not?

In which case it would have been a case of fishy-thing to land-tetrapod to fishy-mammal to fishy-thing.

I don't think there is any reason why it couldn't happen. Things start small, go big, go small, grow legs, lose them etc etc. So, not impossible.

It's like hacking a hole into a piece of wood. You can't undo the hole. Not only that some things can't evolve backwards because it would kill the organism. Fish gills became our ears (or our jaws, I can't remember), if they "evolved backwards" we'd die.

Things can continue to evolve to suit their environments. If they have organs they don't need these may be reduced or somehow removed. The island effect (or whatever it's called) has organisms become smaller so that they need less food if they live in an environment with sparse resources suited to them. Maybe this is what you mean by evolving backwards. Because evolution is generally a change which means an organism is better suited to its environment evolution will only improve on what there is and that isn't going backwards. There are acceptions where evolution happens by random chance because of things like genetic drift so the change might not always be because of natural selection.

Originally posted by melatonin
Depends how you define complexity. How do we measure it?

Is a dolphin less complex than its closest ancestor? Is a snake less complex than a lizard? Is an ape less complex than a monkey? Is a blind shrimp less complex than a sighted shrimp? Is a human less complex than lower mammal?

In each case we could view some degree of complexity ---> simplicity (e.g., limb to fin; tail to no-tail; legs to legless; sight to blind; cellulose-digesting caecum to human appendix).

Judging by what you have said, your view of complexity is similar to mine - complexity can be measured purely and simply by the # of working parts.

Most living beings on earth are marvellously complex, even plants.

I believe that what seperates humans beings from non-sentient creatures is the brain, which is of course how most people differentiate between Earth's native organisms.

However, as opposed to merely saying 'our brains are bigger' or similar, i prefer to go along with the idea of 'massive amount of individual parts stored in a single area'.

Really, our brains are just like conventional microchips, except with millions of individual transistors.

I recall from somewhere that microchip technology is slowly but surely catching up with the human brain, as such it may be the case that sooner or later human beings will understand the complexity of biological reality enough to recreate the human brain from scratch.

It would be interesting, if not a little freakish, to be able to carry around a back-up brain.

P.S: Can evolution go backwards?

Nope, because that would be evolution going forewards, it just so happens that it's turned around on itself.

[edit on 27-11-2007 by Throbber]

You should think of evolution more as adaptation, not growing in complexity, though that is how it normally seems.

Life adapts to changes in its environment. We've grown smarter because we bred intelligence. "The strongest survive"

There may come a day (maybe not too too distant) when we no longer require our intellect as we develop computers to do all our thinking for us.
Than maybe we will start to "devolve" - beginning with the brain.
LOL - A case can be made that it has already started happening for some of us.

I have to agree that evolution cannot go backwards as that would be illogical - it must go forwards whether or not we increase or decrease in complexity or not.

Here's a small snippet showing how an animal can evolve to be one way and then re-evolve back to its original state.


G

Evolution can go backwards. Sort of. The process is called atavism.

i just read to OP so if I am repeating another's post, forgive me.

I don't think there is such a thing as (de)evolve, unless you consider evolution to be positive and (de)evolution to be negative. even so i see evolution as a cycle: "the wheel is turning and it wont slow down, you cant let go and you cant hold on, you cant go back and you cant stand still, if the thunder don't get you then the lightning will".

I am sure some evolutionary changes are not desirable where as others are, but I still dont think this is (de)evolution it is just another step towards oblivion.

I guess i am trying to say there is no "backwards" in evolution. it is not surprising people wonder about this with our mental understanding of the world being dominated by binomials, a gift (?) from the enlightenment.

reply to post by tommyknockers


I agree.

In fact, why do we exist in a world that is entropic (everything reduces and breaks down to simpler less complex forms / order--->disorder) that somehow many believe this theory that nature has an exclusion to that just for the benefit that some not believe matter was created?

reply to post by ben91069


the entropy argument has been refuted and refuted and refuted...

alright, entropy within the universe as a whole works... but on the scale of our teeny tiny terrestrial system... evolution makes sense.

Originally posted by madnessinmysoul
reply to post by ben91069

 

the entropy argument has been refuted and refuted and refuted...

alright, entropy within the universe as a whole works... but on the scale of our teeny tiny terrestrial system... evolution makes sense.

Oh, well it must be true then if you say so. Even on our terrestrial scale, entropy works - what are you talking about? Are you saying it only works on the universe at large?

Let me tell you a secret. It makes no sense to me as it is too unpredictable and self-contradictory. For example, it is possible to evolve into a self-destructive entity, which denies that we evolve to be the survival of the fittest. Is killing yourself by whatever means, survival?