This is quibbling over definitions. In the context of discussing evolution, most people would call the most recent common ancestor of extant apes an ape as well. So humans did evolve from apes, just not any of the existing species of apes.
False. We do not share a common ancestor with all other apes; we share a common ancestor with some other apes, and that common ancestor was very much an ape itself.
We are nested within the ape clade, not a sister clade to it.
“Devolve” is a meaningless term. And dogs are already wolves; just as we can’t turn “back into” apes, domestic dogs can’t turn “back into” wolves.
They may well become more feral and “undomesticate”, but that wouldn’t be “devolution”.
http://www.metacafe.com/watch/732748/is_that_were_we_heading_to/
(Intro to the movie “Idiocracy”.)
There’s no sort of “snapback” in evolution. A dog’s a dog and it will evolve as it does. There’s no question they would evolve differently that if it were to remain domesticated but there’s no reason they would evolve into a wolf, though if the environment best favours more wolf like traits there’s no reason they wouldn’t. Indeed there are feral and wild dogs descended from domesticated animals.
I know you know your stuff, but the sentences I underlined really need to clarified, since a simple reading of them is contradictory.
Judging by the mess in which some people keep their living quarters I would say it is entirely possible.
I’m somewhat confused by this. I mean, if we go far enough back, we of course share a common ancestor with all other extant apes (and all other lifeforms, as far as I know); are you saying that this ancestor isn’t itself an ape? Is the classification ‘ape’ even meaningful then, if its members don’t share a common lineage?
Sorry…the hazards of posting in a hurry. Read “most recent common ancestor” for “common ancestor” in my previous comments. We certainly share a common ancestor with all other apes; however, we share a more recent common ancestor with certain apes (namely, chimps and bonobos) than we do with other apes.
Thus, we are nested within the ape clade. If the common ancestor of all apes + humans were the most recent common ancestor, then we would be a sister clade to apes, and claims that we did not evolve from them would then have merit.
Man, it really IS taking us longer that we thought to get rid of the idea of “degeneracy” of descent.
The short answer to the referred girl’s statement is:
“EVOLUTION DOESN’T WORK THAT WAY!”
If anything, people could “evolve into” damn, dirty post-humans, instead of into supermen (which in any case is just as erroneous – an uber/untermensch species could branch off from humans but WE would not “evolve into” them), but not “back” into the “lesser” primates.
You could argue that dogs still ARE wolves, since they can still breed with wolves.
But semantics aside, it’s entirely possible that wild dogs over time could come to resemble wolves more than they resemble the typical dog of today. Most of the wolf-type alleles are probably still present in dogs in low frequencies, maybe segregated into different breeds. With humans and human-altered environments gone, those alleles could reenter the common pool and may increase in frequency while dog-type alleles are selected against. Then dogs would become to look and behave more like wolves. It’s also possible that dogs would drift towards some other niche and become less wolf-like.
FYI, devolution does exist-- but it’s technically not devolution, if you catch my (genetic) drift.
Example: the stickleback.
Any directionality to evolution is purely an artificial, human construct that we place on it based on our observations. The trout in my stream has no idea what its ancestors look like, and couldn’t care less whether its kids look more or less like them. All that matters is what works. There is no forward, there is no backward. If you want to refer to an instance in which a species picks up a trait that was present in one of its ancestors as “reverse evolution,” go nuts. But the phrase has no real biological significance.
Aren’t those two sentences that I underlined actually at odds with each other? If all that matters is what works, then evolution tends to produce better-working designs, giving it a natural direction towards greater adaptation – and indeed, evolution is basically the maximisation of survival fitness; how’s that (towards greater survival fitness) not a direction?
Because there is no perfect model for survival. A creature which is perfectly adapted to living in the desert would be in trouble if there was a sudden flood, for example.
You have a point, but what Bisected said. What works now might not work tomorrow. More importantly, in my mind, is the sense that when you say “forward” and “backward”, many people will mistakenly infer that there’s some goal that we’re working towards. There isn’t. That’s really the point I’m trying to hammer home, in a possibly less-that-precise way.
However, the nature of that “greater adaptation” is the trick; it may trend towards a more complex or a simpler form. It may be that of a former, more “primitive”, condition, or it may be in the form of a novel phenotype. There is no fixed “direction” in which populations must change over time.
Old, new, simple, complex - there is no evolutionary law stating that lineages proceed from one to the other condition only.
I hear you all very well, and I of course agree that the common notion that there is some teleological goal or purpose to evolution – that there are lifeforms that are ‘more evolved’ than others, by implication – is one to be fought, and by no means would I want to suggest that there is one simple measure for fitness or adaptedness, but still, nevermind the fact that it’s not a singular goal to be achieved by some perfect lifeform, you either develop towards greater fitness, or you die out (or you reach some form of at least temporarily stable equilibrium). That if the desert suddenly turns into an ocean all your previous adaptive traits are going to be worth fuck all doesn’t impinge on that point, in my opinion – you now either adapt to the new environment, or, again, you die out. It’s true that this is not an a priori goal – nowhere in the evolutionary algorithm is there a command to ‘maximise survival fitness’ – but rather an emergent one: all variants that don’t lead to an increase in survival fitness simply are very unlikely to proliferate.
Viewed from another angle, analysis of an environment enables you to draw inferences on the kinds of animals that might live there – animals within a desert need to be able to conserve water in some way, animals that live in water probably are streamlined to some degree, things like that. Thus, while you can’t predict anything about evolutionary developments with absolute certainty, the simple requirement of adaptation puts very strong constraints on the space of possible lifeforms within any environment.
The inverse of that direction, what one could take ‘devolve’ to mean if one were desperate to construe it as a meaningful term, would be to develop away from being well-adapted, or, in other words, to die out. 
Well, okay then. I suppose this is where I’d ask where I suggested it’s a sister clade? Particularly since cousin would be a better analogy than sister. Of course, I made no such assertion.
And by apes, I guess I meant The Great Apes. Of course, our most recent common ancestor was an ape, as are we, but it isn’t the same as saying the same as extant apes.
I could have been more specific, but it didn’t seem to be necessary for my point.
Scientists have noted this, like in diabetics. The juvenile onset type commonly appears before puberty, and pre-insulin, most of them would not survive to reproduce (or were obviously sick, and not attractive marriage prospects).
But with insulin, they survive, and thus keep the diabetic gene in the human gene pool. This partly explains the increasing numbers of diabetics in society (though diet may influence that, too).
But scientists don’t call this ‘devolution’ – that isn’t a scientific term at all. If anything, this is related to ‘hybrid vigor’ – somewhat an opposite of it. And this isn’t always bad – these same genes may be good for something else. The same genetic ‘flaw’ that produces sickle cell anemia in some blacks also gives them some immunity to malaria.