Is there a limit to evolution?

dimensionless

Are Earthian biological systems, in their present state, more complex than they were 200 million years ago? Do evolutionary adaptations reach a limit in terms of they're effectiveness?

Perhaps I can restate this question. If a species from 200 million years ago was transported to present day Earth, would it become invasive species and proliferate (like some imported exotic species do), or would it be wiped by various modern species that have had more time to evolve?

Evo

There is this huge misunderstanding of the saying "survival of the fittest". What it means is "survival of what fits in right now". It has nothing to do with being the strongest or the smartest, it simply means at that moment it made sense, so it survived at that time.

Pythagorean

I might would say reproduction of the fittest

There were amphibians at that point, so complex animals had evolved so there was probably some more complex species that didn't survive, perhaps because they were too complex, perhaps not because of complexity at all. What do you mean by complex anyway?


Like Evo said, the fitness landscape is changing, and there's probably mostly always a "higher peak". An organism might easily find a local maximum in their efficiency, but the global maximum might never be reached before it changes.

I think would be hard to predict. I hear people speculate that our germs would probably wipe out anybody (thing) from the past because their immune system hasn't developed along with their new environment; I don't know much about immunology, so no idea how true that is.

The predator-prey and resource availability issues would have to be retested against the organism's skill set. It's a new environment, so seemingly useless traits could suddenly become useful (and vice versa).

dimensionless

It is a good question. I see many, maybe too many, references to animals as being "primitive," for example sponges are often called primitive. I am trying to ask if modern lifeforms have adaptations that typically make them more fit than older lifeforms when placed in an arbitrary environment.

I suspect that there are many adaptations that have evolved with in the last million years that would have been beneficial at any time during that last two billion years. I am thinking of thinks like better protein metabolization, better recovery from injury, lower metabolic rates during dormancy, etc.

There are some adaptations such as complex eyes, which have evolved many times. In contrast, other adaptations such as horizontal gene transfer, or for that matter, deoxyribonucleic acid itself, which may have only evolved a small number of times.

BlackTentacle

Organisms that have not changed much over time are called 'primitive' e.g. sharks and crocodiles. I don't know what the data is exactly. Primitive species are very successful hence the lack of their need to evolve (adapt).

I guess to answer further would need a specific species. Does the environment it evolved in still exist. Oxygen levels are one thing that have changed.

Drakkith

Are you asking if "modern" species are more adaptable to changing conditions or a wider variety of conditions in their environments thanks to previously developed traits or genes?

BlackTentacle

I would also have to ask why you felt the need to refer to 'Earthian' biological systems. Are you an invasive species Dimensionless?

nucl34rgg

Evolution is simply the change in genetic frequencies in populations over time in response to the driving forces by the environment. If the environment is stable with respect to its effects on the population, then evolution will cause the parameters under selection to "climb the hill" in the fitness landscape, and stabilize at a local maximum to maximize fitness. Once this has been reached, if the environment remains relatively stable, the frequencies will no longer change much.

If there are changes in the environment, the population parameters will adjust accordingly over time to maximize fitness in response, or the population will go extinct. Evolution is not a progression from "simple" to "complex." The propensity for a species to become invasive is determined by its ability to effectively colonize, spread, and for lack of a better word, thrive, in a different environment. Some environments may, for example, have predators that would keep the species population in check, but when introduced to a new environment without the aforementioned predators, the species can be classified as invasive in that environment.

See http://en.wikipedia.org/wiki/Brown_tree_snake as an example of this.

Trakar

"Evolution" is simply the ability of a species to fundementally alter itself in the pursuit of self advantage. To that end, I would say "no."

Ken Natton

If one takes the long view of evolution then the trend from simple to more complicated is apparent, but it does not follow that evolution is about ever increasing complexity. And the answer to the question posed in the thread title also depends on whether you take a more detailed or a more general view. In the short view, absolutely there is a limit to evolution. As has been said, a mouse cannot suddenly sprout wings. All evolutionary change is small and incremental – tiny adaptations to what a species already has. But what is demonstrated by the very diversity of species existing today, all evolving from a common and very simple start, is that, given enough time, there does not seem to be much limit to what evolution can achieve.

Antiphon

The problem with the analysis in this thread so far is the lack of consideration for genetic entropy.

The OPs question could be expanded like so: is natural selection and mutation a process that can go "forward and backward?"

For example can you in principle create an environment which if sustained long enough would result in the re-evolution of something like T-Rex? Or is that genetic pathway gone for good?

Evo

Bolding mine. This is a common misunderstanding. Evolution is not a progression.

I love this video from Khan Academy. It's funny, simple, and clear.

http://www.youtube.com/watch?v=GcjgWov7mTM

Ryan_m_b

Evo has addressed the first part of your post but just for interest look into convergent evolution, organisms under similar selective pressures can evolve similar or the same responses.

To the OP the question is really best addressed by a fitness landscape. A species will proliferate if they are the best adapted, dropping animals at different points in history is unlikely to put them in environments they will thrive in (especially due to lack of food) however it could potentially go the other way.

BWV

well the poincare recurrance theorem could support the idea that a T-rex would "re-evolve" from exisiting organisms but the time / odds would be astronomical and would have nothing to do with whether it is more or less "advanced" than other creatures currently living

as Stephen Gould pointed out, evolution has tended toward greater complexity because that is the only way it can go - the niches for simple organisms got filled long ago and there is a minimum complexity before you just get to a pile of inert chemicals

Antiphon

Very good video. I didn't mean to imply a generic progression but rather a stateful walk. The video itself refers to "accumulated changes". I want to know if there's a biological version of the ratchet and pawl embedded in the accumulation of genetic code.

I don't doubt that with enough selection pressure you could make a chicken resemble a dinosaur. But maybe not. Maybe the ordered sequence of accumulated changes that is the modern chicken can't be undone for some reason.

neen

Short answer; if it was done it can mathematically be undone.

More substantial answer: Do not think of a chicken being subject to enough selectional pressures...instead think that a chicken and it's descendants and their descendants, etc... would randomly produce variations that not only changed the genetic code of the chicken but also eliminated the unused coding. The loss of genetic information that does not affect the fitness of the species are harder to "select" against. It would take very precise genetically selected pressures to eliminate the ordered sequences of accumulated changes. Even if you were to replay the worlds timeline backwards and slowly change the environment back to prehistoric times in the exact same fashion that it had progressed...you would still end up with two genetically different species (chicken and T rex).

mazinse

we wont be getting super powers if that is what you are thinking.