Oh man... That is just beautiful.

NICE!!!

I think there's something too inaccurate. Moe goes back in evolution and transforms into a some kind of rat. I think that one of the laws of evolution is that evolution can not go back, it always goes forward, whatever the new step will be. They could have portrayed Moe as a Neanderthal and then Homer could have render him extinct hitting him in the head with a club.

Nice!!

Is this segment right before they roll the credits in the beginning of the show?

Anyone know the name of the song played in the beginning? It sounds like something by Philip Glass.

There aren't evolutionary laws per se, and as such there isn't anything in particular to prevent evolution 'going backwards' - it just doesn't. There are minor examples which you might consider evolution reversing:

1) Pressure promotes the survival of indivudals with specific genes, pressures then change to promote the survival of those without these genes so these genes are supressed, pressure then changes again so the genes are expressed again.

2) On a more phenotypical level: blind cave creatures have no pressure to maintain working eyes, so most of them lose their eyes functionality. Some even (because eyes are a structural weakness) stop growing them, or grow coverings over them. IIRC the Astyanax Mexicanus cave form does this.

3) Broadly speaking if the same selection pressures which caused a phenotypic change were reversed in the right order then you could promote a 'reversal of evolution'. If you were a god and manipulated the world in the right manner to promote the supression or deletion of genes in the reverse order from which they developed, you could engineer an effect similar to evolution running backwards... probably.

I think the Moe bit was just supposed to be funny.

Please, some kind reader, tell me if I am completely wrong.

You are wrong. There are many reasons for the wrongness, but you might start by looking at neoteny.

Robert:

It's not accurate to say that evolution "does not go back", there is actually no inherent direction to evolution. There are many observed instances of an adaptive trait being gained, and then lost. A quick example would be snakes, which have lost their limbs and reverted to a worm-like shape. However, the odds of ALL of an organism's traits simultaneously reverting to some arbitrary previous synchronous state - i.e. a horse evolving into an animal that looks exactly like a devonian lobe-finned fish, are so large as to be considered impossible. But again, this is not because evolution moves 'forward', there's no such thing.

Duncan makes good points. One can also look at atavism too as a way of seeing how evolutionary throwbacks can occur.

I think you guys are reading too much into this though. It's a cartoon. Sit back and have a laugh. If you're going to criticize The Simpsons on accuracy, we should have started with the fact that prokaryotes don't say "D'oh" because they don't have a vocal apparatus.

Directionality of evolution toward "higher forms" has to be somewhere in the top25 of evolution misconceptions.

Daniel - As many above have mentioned, "backwards" evolution exists plentifully. One of my personal favorite examples is the sea cucumber which through evolutionary time evolved from a bilaterally symmetrical worm, into a 5-fold symmetrical echinoderm, and then back into a bilaterally symmetrical "worm".

MikeC - I'm not sure neoteny is the best example of regressive evolution though. It implies that earlier developmental forms correspond to earlier evolutionary forms which is a restatement of the "ontogeny recapitulates phylogeny" fallacy. But you might be arguing that neoteny is just as much "backwards evolution" as any of the other examples are, in which case I agree.

MikeC #2 There is a kernel of truth in the idea that evolution leads to increasing complexity. After all, complexity is non-negative, and evolution started in an abiotic world of zero complexity - therefore it had to go up. A reasonable guess is that evolution favors monotonically increasing complexity up to some steady state (complexity measured across the set of all evolving organisms, not just within a single lineage). Cheers!

Thanks!... I would have never expected such rightfulness... or truthiness. What's your job Duncan? OK I learnt the lesson. Now I know that the concept of a direction or an objective in evolution is stupid. Evolution is just a thing that happens, theres no will, decision or any other mind-feature involved in it.

Although, Moe-Neanderthal killed by Homer-Crogmanon it's better, no doubt about it.

Daniel - relatively often creatures will reacquire superficial traits they had in the past. Extraordinarily rarely (read almost never), however, does this backwards change come about by the exact reversal of the intermediate changes.

Good points. A species cannot revert to an earlier ancestor species. Reacquiring ancient traits would always result in a new and different species even though it may appear superficially similar. So yes, there is in some sense a direction, but nothing to prevent species from 'superficially' evolving 'backwards'. In the clip, (the species) Moe doesn't evolve into a rat, but something that superficially resembles a rat, which is entirely different.

Was that all part of the couch gag? I missed this week's episode, unfortunately. Fantastic.

It's fairly silly to critique the accuracy of The Simpsons, but if we were going to, it seems to me the biggest inaccuracy is the linear trend portrayed in the bit. It's not as if reptiles became rodents, which then became primates, etc. The branching and diversification that is so fundamental to evolution was ignored in the cartoon. Not that it would have made sense any more had they included it.

I loved Mrs. Skinner as a pterydactyl though. "GRAAH!"

Mike, there's no reason a species couldn't revert exactly to an earlier one. Genetic mutations are the underlying mechanism for evolutionary change, and these are completely reversible. In order for that to happen though, you'd have to have a change in selection pressures that made what was previously selected for a liability instead of an asset relative to a previous state. Furthermore, over any longish period of evolution, the chances that exactly the same regions of the "solution space" would be explored are slim, unless somehow there is an extremely narrow set of genetic configurations that gives rise to phenotypes that are able to survive in a given environment.

So yes, it's pretty unlikely over long separations and in organisms with more genetic material to "play with". But not impossible.

This is great!

I think that one of the laws of evolution is that evolution can not go back...

Not necessarily. There are evolutionary throwbacks after all.

Daniel, when the gene for an action, fuction or behavour becomes obsolescent to the living organism, it is switched off, not eliminated.

Visible expressions of this rule lies in our vestigate tailbone and the leg bones of whales.

Such genes can be turned on should our environment change and a need arose again.

The way we are made indicated that anything that may be useful will be shelved away for potential use.

While the design of our bodies are far from perfect, it is eminently thrifty in the way it hoards useful materials and in adapting diverse parts of our living cells to create new organs or mechanisms within our bodies.

This is what I know based on what I have read so far.

Evolution seems to be a process that takes the long view on things.

What we see as regresion or progress is based only on our limited understanding of the short term of things.

I recently emailed my favorite evolutionary biologist Dr. Zach from the Evolution 101 podcasts that I provided to you guys a while back.

I used the arguments you guys used to make my point in the email and here is Zach's reply:

Well, you have to remember that evolution doesn't really have a direction in mind in the first place. Evolution does not start with species A, having species Z in mind as the final product. Evolution is a process that continually optimizes a species for its changing environment. It's possible that if an environment changes significantly to return to the conditions which resulted in the traits of an ancestral species, it's likely that those same traits will be selected for in a descendant species. But it wouldn't be a full-reversal, i.e., the descendant species could not "become" the ancestral species again.

Whoops, lets try that link again.

Evolution 101 podcasts

way we were "made"? "design" of our body? "shelved away for future use"? kes, have you gone ID on us?

i'm only playin', but i do find it interesting how hard it is to avoid this kind of terminology in a discussion on evolution.

I think Homer and Moe just ran into each other on their way home. Moe happened to be walking in the direction where time flows backwards.

South Park version:

http://www.youtube.com/watch?v=7ba_qvDRAtk&eurl=http%3A%2F%2Fnecromanc%2Eblogspot%2Ecom%2F2007%2F03%2Ftheory%2Dof%2Devolution%2Dsouth%2Dpark%2Dversion%2Ehtml