Gould's theories on evolution

[mr friendly guy]

Ok, Stephen Gould is a well known paleontologist (not to be confused with the sci fi writer of the same name who wrote "Jumper") who put forward some theories on evolution which contradict neo -Darwinists like Richard Dawkins for example. I don't have any books on his writings, however I do have second hand accounts ie written by others. These include The Evolutionists : The Struggle for Darwin's Soul by Richard Morris which describes the fights between the triumvirate of Dawkins, Daniel Dennett and John Maynard Smith and Gould and his supporters, such as Niles Eldredge of which both came up with the idea of punctuated equilibria of evolution; and also Richard Dawkin's "The Blind Watchmaker".

Gould's (and Eldredge's) ideas have has been seized upon by unscrupulous people seemingly to use it in their crusade against Darwinism through use of straw men. For example there was a debate between Christopher Hitchens and some rabbi (who claimed to have debated Dawkins at Oxford, given that the latter could not remember this debate it was most likely not a formal or even significant affair) hosted on Richarddawkins.net, in which he claimed
a) Gould schooled Dawkins on a debate in evolution
b) Gould doesn't believe in evolution, he believes in punctuated equilibrium (too bad Gould was dead at this point and couldn't correct him), although if Hitchens knew enough about punctuated equilibrium he could have metaphorically slaughtered his opponent.

To reiterate, Gould and Eldredge proposed that evolution occurs in fits and bursts with periods of stasis in between. This was based on studying preserved fossils of snails (Gould) and trilobites for Eldredge. This idea is known as punctuated equilibrium. Note, this is not to be confused with saltatism, which proposes that evolution occurs from macro mutations within the space of as little as one generation. Also not to be confused with pokemon evolution which occurs even faster (I put this in as some writers to my local paper seem to think evolution acts like pokemon minus the pokemon battles, ie in the same generation and through acquired characteristics, in other words Larmarkianism on steroids).

Now this doesn't really contradict neo darwinism in that large a way IMO. It may shed light on the rate of which evolution occurs, and really those seizing on it as anti-evolution propaganda are just betraying their desperation. However it does lead to a few implications such as...

a) why is there such long periods of stasis?

Gould proposed there were some factors which oppose natural selection, and evolution only wins out during certain circumstances, for example environmental change which leads to speciation. It also leads to the implication that species tend to evolve by splitting into 2 species, rather than one species gradually evolving into the other.

Some of these factors are genetic, and natural selection itself, following the rule of "if it ain't broke, don't fix it". This seems to be suspect to me, as Dawkins and Dennett point out that if this was the case, breeders would have initial resistance breeding for traits. Moreover if no environmental changes occur, there is not much evolutionary pressure for natural selection to change the species, thus it seems philosophical to me whether you say natural selection works to NOT change the species or whether its simply in "neutral" (I was going to say "off" but thats not accurate).

I am unclear as to what they mean by genetic factors, although the grand old man of evolution Ernst Mayr did propose that new mutations will diffuse slower in a large population, thus this may be a factor into why evolution works slow.

Note Richard Dawkins would argue that the stasis you are seeing is simply could simply be due to migration, ie the species evolve elsewhere and then migrates to where their eventual fossilised remains are found. This is actually not that unreasonable given we predict evolution should occur when their is change in environment which in this case is due to migrating to a different environement. However that is tangential to what I am interested in, namely understanding Gould's theory.

b) Other mechanisms besides natural selection.

So evolution works through random mutations (random in the sense that they don't occur with the point of view of improving the species for survival) and natural selection (which is non random, since it does have an end "goal" - survival). All participants in the debate agree that natural selection is the main process which drives evolution, however Gould proposed another mechanism, called "species sorting"

It was clear to me what exactly he meant by that, however wikipedia gives this as the definition

Species sorting is a theory which states that each species will eventually have its own ecological niche as two species cannot occupy the same niche for an unlimited amount of time without extinction. One will be more competitive than the other species. Therefore, if two species with the same niche were left in the same area, eventually one of the species would evolve and participate in resource partitioning.

Generally Gould uses this to explain why some animals, eg beetles have over 500 000 different species, while others have only few. He also mentions some species are more prone to give more lineages than others, although the mechanism is not clear. If the wiki definition is correct, it seems like species sorting just describes the end result, rather than a process per se.

There are a few aspects of what Gould says which isn't quite clear to me, and I was hoping that others on this board could help me. Namely

a) what are these genetic mechanims Gould proposes which explains so call stasis.
b) how does species sorting work, since as mention it seems to me to be describing an end result rather than a process per se... which leads to
c) how does species sorting led to some lineages having more species, since I would have thought ecological and geographical partitioning will be the events which force evolution to work

[Alyrium Denryle]

Now this doesn't really contradict neo darwinism in that large a way IMO.

It really does not. To be perfectly blunt, the two concepts are not mutually exclusive, and in fact are unified. More about this in a second.

It may shed light on the rate of which evolution occurs

Under certain conditions... Nail--->head.

Gould proposed there were some factors which oppose natural selection, and evolution only wins out during certain circumstances

Ok. Bit of confusion here. Evolution=/Natural selection. Evolution is the simple fact that organisms change through time. Natural Selection (and all it entails) is one of the mechanisms that drive this. Other mechanisms being mutation rate, and genetic drift.

for example environmental change which leads to speciation. It also leads to the implication that species tend to evolve by splitting into 2 species, rather than one species gradually evolving into the other.

Speciation occurs at the level of the population. IE. a population becomes genetically distinct from other populations of the same species that are either physically separate from it, or otherwise reproductively isolated. These conditions need to be met to avoid gene flow.

Some of these factors are genetic, and natural selection itself, following the rule of "if it ain't broke, don't fix it". This seems to be suspect to me, as Dawkins and Dennett point out that if this was the case, breeders would have initial resistance breeding for traits.

Not really. This is called an Evolutionary Stable Strategy(in behavior anyway... in general it is referred to as Purifying Selection), where the fixed trait (allele/epistatic/QTL... whatever) cannot be invaded by another alternative trait because it is the best possible one given the selective pressures at the time. If selective pressure shifted (such as the intervention of a selective breeder) then any mutation that came along may be favored by these new selective pressures. However it is worth noting that any new point mutation has a high chance (depending on litter/brood/clutch size) of drifting out of the population within 5 generation, and the effects of selection on this are almost irrelevant unless the selective pressures are VERY strong. So said selective breeder would need to wait a while before a mutation he might wish to select for would come about, and be able to be selected for.

Moreover if no environmental changes occur, there is not much evolutionary pressure for natural selection to change the species, thus it seems philosophical to me whether you say natural selection works to NOT change the species or whether its simply in "neutral" (I was going to say "off" but thats not accurate).

Natural Selection does not act "in order to do" anything. It is unplanned. If fitness is highest with trait X, it will select for trait X, if a new mutant comes along that is superior in a given environment (even if that environment does not change) then if that mutant does not drift out, it will become fixed.

It is worth noting that if a new mutant is neutral, because of drift it can still become fixed but the probability is very low.

Neutral variation however can form a substrate upon which a rapid environmental change can lead to rapid evolution. Imagine the following scenario. Mutations accrue in the population that permit some lizard's enzymes to work at a wider range of temperatures without becoming inactive or denaturing. More accrue that decrease the specificity of their anti-predator responses. In their usual environment these are all neutral. Say the environment changes, and so does local species composition, all of the sudden those neutral changes become rapidly fixed in the population. This application of neutral theory is called Genetic Charge, where neutral polymorphisms accrue in the population and when the selective pressures shift, provide a substrate for rapid evolution.

I am unclear as to what they mean by genetic factors, although the grand old man of evolution Ernst Mayr did propose that new mutations will diffuse slower in a large population, thus this may be a factor into why evolution works slow.

Mutation rate is low, and selective pressures not usually large enough to overcome drift. The larger the population, the weaker drift is, which means that selection acts more strongly.

Note Richard Dawkins would argue that the stasis you are seeing is simply could simply be due to migration, ie the species evolve elsewhere and then migrates to where their eventual fossilised remains are found. This is actually not that unreasonable given we predict evolution should occur when their is change in environment which in this case is due to migrating to a different environement. However that is tangential to what I am interested in, namely understanding Gould's theory.

Gould also could not sample everything. The simple fact is, fossilization is a rare event, and we basically only get snapshots from very good, isolated fossil beds.

b) Other mechanisms besides natural selection.

So evolution works through random mutations (random in the sense that they don't occur with the point of view of improving the species for survival) and natural selection (which is non random, since it does have an end "goal" - survival). All participants in the debate agree that natural selection is the main process which drives evolution, however Gould proposed another mechanism, called "species sorting"

It was clear to me what exactly he meant by that, however wikipedia gives this as the definition

Therefore, if two species with the same niche were left in the same area, eventually one of the species would evolve and participate in resource partitioning.

It has been well known for a long time, and it does not lead to rapid spurts of evolution.

a) what are these genetic mechanims Gould proposes which explains so call stasis.

Mutation rates are very very low, and most mutations, even beneficial ones, drift out. Most of the rest are either deletarious or neutral at the time. Neutral variation can accrue though, providing a substrate for rapid evolution. Gene duplications are rare events, which allow for evolutionary tinkering.

b) how does species sorting work, since as mention it seems to me to be describing an end result rather than a process per se... which leads to

What happens is that a population of two species (A and B) (because of a migration event, or continental movement) which occupy the same niche come into contact. Competition is bad for both. As a result either one population goes extinct, or they relieve competition by diving the niche. So that say species A specializes on living in one part of a tree, while species B specializes in the other part They become species C and D. Other populations of species A and B still exist, and are not in contact with eachother.

This process however is common on geologic timescales and does not count as a punctuation of equilibrium.

c) how does species sorting led to some lineages having more species, since I would have thought ecological and geographical partitioning will be the events which force evolution to work

they are pretty much one and the same... SOme lineages have more species because they are better dispersers (and thus come into contact with others more) or occupy labile enough niches to make the niche partitioning easy.

[Broomstick]

Ok, Stephen Gould is a well known paleontologist (not to be confused with the sci fi writer of the same name who wrote "Jumper") who put forward some theories on evolution which contradict neo -Darwinists like Richard Dawkins for example.

I wouldn't describe it as contradiction so much as a dispute about mechanisms. Of course, it did get pretty heated at times, scientific discourse can be like that, but both camps are solidly Darwinist.

I don't have any books on his writings, however I do have second hand accounts ie written by others.

As always, going to the original is best - but then, I own almost all of Gould's book form published works for the general public (I do not have the compete run of his magazine essays, and there are a few publications such as textbooks and scientific articles I haven't read). Gould's 40 years of publications is both a blessing (his viewpoint is in front of a lot of people) and a curse (because his ideas and theories changed over time, and opponents can cherry pick items to fit their own ideas regardless of whether or not Gould later changed his views based on new evidence. The most obvious example of this being Gould's essay "The Reversal of Hallucigenia" where, based on new evidence, he stated his earlier essay on the Cambrian fossil was in error and discussed how limited fossil evidence can lead to wrong conclusions, the bias of viewpoint, and the important of altering one's views to fit the facts).

Gould's (and Eldredge's) ideas have has been seized upon by unscrupulous people seemingly to use it in their crusade against Darwinism through use of straw men.

Which would be funny, given what an adamant evolutionist/Darwinist Gould is, if people didn't take these things so seriously.

b) Gould doesn't believe in evolution, he believes in punctuated equilibrium (too bad Gould was dead at this point and couldn't correct him), although if Hitchens knew enough about punctuated equilibrium he could have metaphorically slaughtered his opponent.

Which is ridiculous - punctuated equilibrium is an evolutionary mechanism, like natural selection or sexual selection. It is an attempt to explain how evolution happens, not a refutation that evolution occurs.

To reiterate, Gould and Eldredge proposed that evolution occurs in fits and bursts with periods of stasis in between.

That's the sound bite - they never denied the possibility of other ways evolution occurs, a theme that is consistent throughout Gould's writings. Punctuated equilibrium attempts to explain a feature of the fossil record, a feature that has been problematic since Darwin's day and which Darwin himself commented upon as a problem for his theory: the fossil record seldom shows graduated changes from one species to another, rather, it shows species being relatively static over time, then suddenly disappearing while new ones suddenly appear. You have to explain this somehow. Darwin speculated that it was due to an incompleteness of the fossil record. Gould and Eldredge believe (and their theory revolves around this) that this is not an artifact of how and where fossils are formed but is actually showing a significant fact. Gould does discuss that, due to how fossilization occurs, that record is and always will be spotty to one degree or another, some environments are more conducive to preserving fossils than others which skews what we see in the rocks.

Punctuated equilibrium tackles a problem that Dawkin's "selfish gene" theory doesn't touch at all - that is, the nature of the fossil record and what it tells us about evolution and the history of life. My reading is that the dispute between Gould and Dawkins was whether selection occurs at the level of genes or at the level of individuals (or some other level, for other Dawkins critics). Punctuated equilibrium can exist regardless of the level at which evolution occurs, it is possible that both Gould and Dawkins are right (and that both men's theories will subsequently be altered and refined in the future based on additional data and discovery).

a) why is there such long periods of stasis?

Gould proposed there were some factors which oppose natural selection, and evolution only wins out during certain circumstances, for example environmental change which leads to speciation. It also leads to the implication that species tend to evolve by splitting into 2 species, rather than one species gradually evolving into the other.

Incorrect. Gould is very clear that natural selection occurs all the time. Punctuated equilibrium can result in periods of time when species statis is favored, and other times when change is favored. If you're optimized (however you may define that term) for your current niche then you're better off NOT changing, and those that don't change will leave more descendants, resulting in a period of "stasis" (which is not static at all, as the mechanisms of evolution are still in full force). If the environment changes radically, though, you're no longer "optimized" and change may be an advantage, which is how you get rapid speciation.

Punctuated equilibrium, as proposed by Gould and Eldredge does not bar classical Darwinist slow change speciation. It is an explanation of why evolution can occur in "jumps" rather that just in slow change, and why stasis followed by abrupt change may be a frequent mechanism for speciation.

Some of these factors are genetic, and natural selection itself, following the rule of "if it ain't broke, don't fix it". This seems to be suspect to me, as Dawkins and Dennett point out that if this was the case, breeders would have initial resistance breeding for traits.

I disagree with this. Breeders deliberately change the environment of what they breed to favor particular traits, altering the circumstances under which a species exists. A change of environment makes change more likely to be favored, and in the case of deliberate breeding, it definitely favors different traits than a natural environment. In other words, quick change under human selection is entirely in agreement with punctuated equilibrium.

Moreover if no environmental changes occur, there is not much evolutionary pressure for natural selection to change the species, thus it seems philosophical to me whether you say natural selection works to NOT change the species or whether its simply in "neutral" (I was going to say "off" but thats not accurate).

Again, a misunderstanding - if the environment doesn't change then natural selection may well favor NOT changing, if the species is already so well adapted that virtually any change would be detrimental in regards to current conditions. It's in full force all the time. Clearly, natural selection is not in "neutral", it really is working against change in that particular case.

I am unclear as to what they mean by genetic factors

Within the context of your post I'm not sure either. However, some people have brought up things such as "cultural factors" as part of evolution (including Dawkins and his memes)

although the grand old man of evolution Ernst Mayr did propose that new mutations will diffuse slower in a large population, thus this may be a factor into why evolution works slow.

That is true - both that new mutations diffuse slower in large populations and that evolution is a multi-factorial process dependent on environment, mutation rate, and according to some (including Gould) biological constraints on what is even possible to do.

Note Richard Dawkins would argue that the stasis you are seeing is simply could simply be due to migration, ie the species evolve elsewhere and then migrates to where their eventual fossilised remains are found. This is actually not that unreasonable given we predict evolution should occur when their is change in environment which in this case is due to migrating to a different environement.

On the other hand, migrations could occur when the environment changes and the individuals of species seek a new environment closer to what they are already accustomed/adapted to.

b) Other mechanisms besides natural selection.

So evolution works through random mutations (random in the sense that they don't occur with the point of view of improving the species for survival) and natural selection (which is non random, since it does have an end "goal" - survival).

Incorrect. The end goal of natural selection is not survival, it is reproduction. Whoever leaves the most descendants "wins".

All participants in the debate agree that natural selection is the main process which drives evolution, however Gould proposed another mechanism, called "species sorting"

Which doesn't bar natural selection being one of the major forces or THE major force driving all this. "Species sorting" is, in part, a recognition that whoever gets to a location/resource first has an advantage. An already established species in a particular niche is difficult to displace. An invader not only has to be sufficiently adapted to occupy that niche, they also have to outbreed a competitor already in place. There are various ways they can do this, but being more unpleasant for predators to eat, being able to eat your competitor, breeding faster, being resistant to disease, or giving a disease to your competitor all fall under natural selection.

Generally Gould uses this to explain why some animals, eg beetles have over 500 000 different species, while others have only few. He also mentions some species are more prone to give more lineages than others, although the mechanism is not clear. If the wiki definition is correct, it seems like species sorting just describes the end result, rather than a process per se.

Having read Gould's general audience work, yes, "species sorting" is the end result, it's not the mechanism that causes it to occur.

a) what are these genetic mechanims Gould proposes which explains so call stasis.

Gould is basing his theory on observing the fossil record. He's saying "this is what we are actually seeing, mostly it's long periods of stasis interrupted by abrupt (on a geological time scale) change." That is the heart of punctuated equilibrium. He proposes mechanisms, but as I read what he wrote he does state that these are proposed explanations, not claims of absolute fact, and, as I mentioned, he was willing to and in fact did modify his views over time. Punctuated equilibrium can be a valid theory even if it operates by different mechanisms than what Gould and Eldredge originally proposed.

b) how does species sorting work, since as mention it seems to me to be describing an end result rather than a process per se... which leads to

Again - you already have it: species sorting is an end result of natural selection. It's another way of saying "species remain static for long periods of time".

c) how does species sorting led to some lineages having more species, since I would have thought ecological and geographical partitioning will be the events which force evolution to work

Some species are more able to adapt to change than others.

This, of course, has nothing to do with choice on the part of a species. It is due chance, in large part. Certain factors favor certain species if there is an abrupt change in environment, upsetting the status quo. Among those factors are a large and widely distributed population, wide dietary options (if you only eat one thing and that one thing goes extinct you're fucked... but if you eat several things then one of them going extinct won't doom your species), the ability to survive periods of low resources (hibernation, fat stores, etc.), and probably a bunch more. He does discuss in various essays how it seem that widely distributed generalists are more likely to leave descendant species than localized specialists, and also that species able to go dormant seem to do so as well. Of course, there are other species that are specialized and last a long time with little change, but that may be because they favor environments that seldom change, or niches that are common even during times of change.

Gould also maintains that mass extinctions are different than the time periods in between them. He allows for actual random chance to have an effect - you can't plan in advance for a planet-killer asteroid impact. You may be a fantastic species but if the rock falls on top of you, you're fucked, whereas some dab of goo that isn't so great on the opposite side of the planet survives just because it wasn't in the blast zone. This concept pisses some people off, they just don't' want to accept that random chance really exists despite evidence to the contrary. He proposes that what enables a species to survive a mass extinction event may be very different than what enables a species to survive in more typical times. He does not, however, hinge his punctuated equilibrium theory on this - on the contrary, these speculations are the result of punctuated equilibrium and exploring possible consequences of it.

Keep in mind, too, that species can be separated in time even when occupying the same territory. Time of mating, for example, can be genetically controlled. Any population will have some variations in that timing among individuals. In many cases, breeding early or late will doom your offspring, but if it does not, then part of a population may breed early and part late and, over generations, that timing could become obligatory, resulting in two closely related species that could interbreed but don't due to timing of the mating season. Over more time, these two species should diverge more and more, until eventually they truly are entirely separate and unable to hybridize any longer. There is even some evidence for this occuring. Punctuated equilibrium does not bar that type of gradual speciation, it states that based on the fossil record that is not how speciation usually occurs.

In other words, a lot of people have a very poor grasp of what punctuated equilibrium is and isn't. It is NOT a refutation of Darwin any more then general relatively is a refutation of Newtonian physics. It is NOT proposing one, sole mechanism for evolution and evolutionary changes. It does NOT dictate the mechanisms of evolution.

Does that help any?

[Rye]

Dawkins deals with PE in the "Puncturing the Punctuationists" chapter of The Blind Watchmaker. Long story short, neo-Darwinism allows for variation in the speed of evolution already in the form of natural selection. You get suddenly different selection pressures, (e.g. in an ice age) you get a "sudden" change in response.

[dworkin]

An analogy I heard from when I was at Uni was "How fast does your car go?". On the open road it can go 100 km/hr (if you don't want a ticket) but more often it's going much slower as in congested traffic and most of the time it's stationary (you've parked somewhere). Evolution is no different, it proceeds at the rate conditions allow.