Robert Broom's thesis is that evolution is finished. Even though his claims are more than 50 years old his observation seems to be well supported by evidence nowadays. It is no way easy to find his antidarwinian thoughts on internet, but something can be found in John Davison's Evolutionary Manifesto - especially the one about evolution of mammalian Orders from 1951:
In Eocene times -- say between 50,000,000 and 30,000,000 years ago --small primitive mammals rather suddenly gave rise to over a dozen very different Orders -- hoofed animals, odd-toed and even-toed, elephants, carnivores, whales, rodents, bats and monkeys. And after this there were no more Orders of mammals ever evolved. There were great varieties of evolution in the Orders that had appeared, but strangely enough Nature seemed incapable of forming any more new Orders.
But it's only a chart. One of the best preserved location when the phenomenon can be observed is John Day Fossil Beds National Monument. These fossil beds contain a rare continuum of 50 million years of plant and animal history, compared with 2 million or 3 million years at better-known fossil beds.
Even if we accept darwinistic claim that mammalian Orders are only naming convention we can neverthenless see that greatest diversification of mammalian Families and even Genera(!) occurs:
The periodof 39 to 20 million years ago (John Day Forma-tion) seems to harbor the greatest diversity inknown fossils of families and genera. Current diversity of families and genera of the basin assess-ment area does not match that of this period...
And last but not at least some ad hoc quotation from internet:
The great diversity of Holarctic primates during the Eocene indicates that at least 90% of modern diversity would already have been reached by the Middle Eocene."
A number of mammal orders show peaks of family diversity around the Eocene-Oligocene boundary, such as Soricomorpha, Rodentia, Primates, Artiodactyla and Proboscidea.
Perissodactyls were once much more diverse... Only seventeen species of perissodactyls remain on the Earth today, a shadow of the group's former glory.
So I see Broom's observation that "evolutionary clock has so completely run down" as the well supported claim nowadays too. Interpretation of the fact that no new mammalian Order aroused during huge time period from Eocene and that mammalian diversity generally seems to be fading instead suggests some "predetermined internal factors" behind evolution and no RM and NS as darwinists suppose.
Perhaps it is not Broom's evidence that is outdated but his view of evolution ?
I note that you do not present a real argument from the data to Broom's claims. I can't tell on what basis Broom reached his conclusions.
Some facts to consider.
1) Taxonomy is based very heavily on life as it exists now. If biologists were assembling a taxonomy 30,000,000 years ago it is likely that some of Brooms Orders would not be recognised as such. Because - based on the species extant at that time - it would not be justified. Broom's data may be at least partially explained as a consequence of this.
2) According to the diagram you link to the new Orders have their basis in the aftermath of the K/T mass extinction event. This is a period where we would expect rapid evolution and disversification. Since there as not been another mass extinction event since then we cannot validly compare the data without making allowance for that fact.
How does Broom address these two points ? Does he address them ? If not, then why not ?
quote:In Eocene times -- say between 50,000,000 and 30,000,000 years ago --small primitive mammals rather suddenly gave rise to over a dozen very different Orders -- hoofed animals, odd-toed and even-toed, elephants, carnivores, whales, rodents, bats and monkeys. And after this there were no more Orders of mammals ever evolved. There were great varieties of evolution in the Orders that had appeared, but strangely enough Nature seemed incapable of forming any more new Orders.
This is not quite true. The Eocene did not suddenly give rise to over a dozen new orders. The linked chart shows quite clearly that these orders began radiating at about the time of the KT-boundary, at the beginning of the Paleocene.
It seems pretty straightforward about what happened. A mass extinction emptied a lot of different ecological niches, which the surviving species filled during radiative adaption, perhaps allowing pretty innovated "designs". Once the niches began to be filled, natural selection then intensified, preserving the best adapted of the new designs in the newly opened niches, and by the beginning of the Eocene pretty standard designs (the different orders) had been established. After this point, large scale changes, drastic innovations would move the morphology off of the peak on the fitness graph, so natural selection would then be fairly conservative in preserving those forms that have proven to be highly adapted, and preventing poorly adapted innovations from taking hold in the now crowded ecosystems.
My guess is that after human race has run its course, the end result of the mass extinction which we have produced will be that the relatively few remaining species will again undergo radiative adaptation, and we would (if we were around to observe it) the rise of many more new orders.
This world can take my money and time/ But it sure can't take my soul. -- Joe Ely
the theory of evolution predicts Broom's observations
So I see Broom's observation that "evolutionary clock has so completely run down" as the well supported claim nowadays too.
Perhaps it has slowed, but to expand on PaulK's second point above, that is not a contradiction of the Theory of Evolution, but rather a prediction of the theory of evolution:
Evolution/speciation is predicted to occur more rapidly when there are many unoccupied niches, which was the exactly the situation after the KT mass extinction. In other words, up until the KT extinction, mammalian evolution was likely as slow as it is today (only two lineages as stated by the 2005 chart you posted). At the mass extinction event, these lineages explosively diversify and speciate (evolve) to fill all of the newly available niches. Once these niches are filled, the diversification again slows, as demonstrated by the posted chart. At that point, most species are generally under normalizing selection to maintain their niche-optimized characteristics (until the enviroment changes), and thus appear to have stopped diversifying/evolving.
These bursts of evolution are often referred to as adaptive radiations, and occur on a much smaller scale as well. The Galapagos finches are perhaps the most famous version of this type of event: A single pair of finches colonized the Galapagos islands, and their descendants evolved over time into fourteen species, each with its own specialized characteristics optimized to the niche it inhabits.
A very important point: Nothing about the Theory of Evolution predicts that diversification of species or lineages should proceed in a regularly timed manner. Instead, such diversification relies on environmental factors (selection), and thus will likely occur in spurts with environmental changes or availability.
Please let me know if you would like any clarification or further explanation. Again - the observation that no new lineages of mammals have arisen since the Eocene is a prediction, not a contradiction, of the Theory of Evolution.
Order is above Family, which is above Genus. (There are a confusing array of subclassifications but that's the basic situation).
There is always a subjective element in taxonomy - even species is not completely objective (it's not unusual for a population previously considered a subspecies to be promoted to full species status).
I think the crucial point which we are missing is the argument supposed to support Broom's conclusions. We simply don't know how the evidence is supposed to show that Broom was right.
I can't find anything either, but I note that the year in your quote is 1910. Although scientists pretty quickly accepted common descent due to Darwin's efforts, there was a lot of controversy over what role, if any, natural selection played in the process. Darwin's theory is about natural selection -- the common descent part is fairly trivial. It is quite possible that Brown accepted a non-Darwinian theory of evolution.This world can take my money and time/ But it sure can't take my soul. -- Joe Ely
As Robert Broom died in 1951, thus being unavailable for comment, I suggest the onus is on those who claim Broom was "anti-Darwinian" to find some reference in his writings that supports that assertion. Does not the fact that such evidence is not apparent, make it equally possible that Broom accepted mainstream Darwinian evolution?
quote:As Robert Broom died in 1951, thus being unavailable for comment, I suggest the onus is on those who claim Broom was "anti-Darwinian" to find some reference in his writings that supports that assertion.
Davison does that in the essay linked in the OP. The quotes seem to show that Broom may have had some tendencies toward structuralist theories of evolution, but it's hard to say what relative importance Broom felt natural selection had in the process of evolution. At any rate, having supplied evidence that does seem to support the claim, the onus is now on others to read Broom's works to find out if these quotes are taken out of context and to find out what role, if any, he felt natural selection has.
quote:Does not the fact that such evidence is not apparent, make it equally possible that Broom accepted mainstream Darwinian evolution?
Darwinian evolution was not the mainstream at that time; rather it was one of many possible theories that were discussed and studied. Common descent was almost universally accepted as a fact; there was still a lot of work to be done to determine the mechanisms of evolution.
It is very conceivable that Broom was not a Darwinian, there is no reason to assume that he was Darwinian, and if he wasn't then this would not count as a stain on his professional reputation.
Without actual evidence, it is hard to say what Broom believed. Davison supplied some evidence that Broom was not pure Darwinian, and now the onus is on those who would like to show that he was (if anyone really thinks this is an important issue). Maybe he was, maybe he wasn't, but I see no problem right now with the possibility that he wasn't.
This world can take my money and time/ But it sure can't take my soul. -- Joe Ely
Broom's evolutionary theory is based on the existence of some sort of 'intelligent spiritual agency' of two types: a) the lower agency, present in animals and plants, of limited vision and limited power, and b) that of a much higher type which has planned and directed evolution (via directing from time to time the former, inferior agencies). Broom pointed to the presence of an uncountable multitude of convergences which cannot be explained satisfactorily by lamarckism or by darwinism. Broom announced that evolution is practically finished, that the physical evolution has stopped but the process continues on a higher, spiritual plane.
The main argument you have presented is that mass extinction during K/T period emptied different niches which the surviving species filled during radiative adaption. Natural selection then intensified, preserving the best adapted. Yet the Eocene period gave rise not only to known land's mammals but also to bats and whales and sirenians. It would mean that there were empty niches not only on the ground but in the air and in the sea as well. Sirenians and whales belong to different mammalian orders, so mammals entered the sea twice independently. It would mean that in the sea there were more convinient niches as in the land for whales/sirenians predecessors. Oddly enough indigenous sea animals did not filled these emptied niches by radiative adaptation but mammals from land overtook them.
This should have happened during Eocene period where there was no strong selective pressure on the land as you claimed. Yet after then selective pressure intensified which led many mammalian orders, families and genera to extinction. Yet after Eocene there was no other succesfull attempt to enter the sea and air. Why? Supposing strong selective pressure on the ground we have to suppose the same - or stronger - selective pressure in the sea and in the air that hinder mammals to reenter it again. Due to strong selective pressure even Pinnipedia did not manage entered the water completely and freezed in their half-state.
On the other hand your theory mean that natural selection seems to be an antievolutionary force that tend to preserve pre-existing species already fully developed. It eliminates, destroy all novelties. So natural selection itself has not much to do with evolutionary progress. Where it is in effect it does not support and care for new solutions. It is not creative force. It just removes extremities - and this is literally in accordance with antidarwinian thinkers like Punnett, Grasse, Heikertinger, Davison.
Might be we should agree with a little bit changed Brooms sentence?
There were great varieties of evolution in the Orders that had appeared, but strangely enough Natural selection seemed incapable of forming any more new Orders.
Broom's evolutionary theory is based on the existence of some sort of 'intelligent spiritual agency' of two types: a) the lower agency, present in animals and plants, of limited vision and limited power, and b) that of a much higher type which has planned and directed evolution (via directing from time to time the former, inferior agencies).
Huh. So Broom was a Lamarckian. Interesting.
quote:It would mean that in the sea there were more convinient niches as in the land for whales/sirenians predecessors.
What this meant was that among one population of Pakicetus, for example, which were living near a riparian or estuarian environment, those that were slightly better able to make use of the water (for protection or as a source of food) were better able to reproduce and leave behind offspring than those that were better suited for an entirely terrestrial existence. Of this slightly more aquatic version of Pakicetus, those that were ever so slightly more efficient at the use of the aquatic environment were more likely to leave offspring than the less aquatically adapted. After a while, you have an aquatic or semi-aquatic version of Pakicetus. Some environmental change causes the completely terrestrial Pakicetus to become extinct, leaving only the aquatic descendent species.
I'm not sure what "more convenient niche" even means.
quote:Oddly enough indigenous sea animals did not filled these emptied niches by radiative adaptation but mammals from land overtook them.
There were probably many empty niches in the oceans -- I believe that the KT-extinction hit marine life harder than land life, but I'm not sure. At any rate, some niches were filled by land animals adapting to the seas, and other niches were filled by sea animals who likewise adapted to the newly opened environments from different niches. I bet that in examining the fossil record one would see an increase in new orders in all surviving classes at this time, including among fish, crabs, and whatever.
quote:Yet after Eocene there was no other succesfull attempt to enter the sea and air. Why?
Maybe the niches were already filled. There was no more room for new entrants.
quote:Due to strong selective pressure even Pinnipedia did not manage entered the water completely and freezed in their half-state.
Sure. If like Broom
Broom's evolutionary theory is based on the existence of some sort of 'intelligent spiritual agency' of two types: ... b) that of a much higher type which has planned and directed evolution....
one has an a priori commitment to some vague Lamarckian force that compels species to evolve in particular directions, then I can see how this is difficult to understand.
But in the absense of anything forcing evolution, particular in the absense of anything forcing evolution in a particular direction, why should they evolve into a more aquatic species? Presumably they do quite well the way they are. Those better adapted to a more purely aquatic life would not fare as well as the present pinnipeds, those better adapted to a more terrestrial environment would not do any better either.
quote:On the other hand your theory mean that natural selection seems to be an antievolutionary force that tend to preserve pre-existing species already fully developed. It eliminates, destroy all novelties.
Sure. It can be. In fact, pre-Darwin that is what naturalists believed that natural selection did. Before Darwin it was believed (at least by the functionalists) that each species was already perfectly adapted to its environment, and that therefore any variation off of the archetype would be less adapted and removed by natural selection. In fact, one of the biggest obstacles to Darwin's theory was that people had a difficult time imagining natural selection as positive, creative agent as opposed to the traditional view of it being a negative conservative one.
And it makes sense. Imagine the graph that measures "fitness" as a function of "morphology". If a species is already at a local maximum, then any change in morphology will make the individual "less fit", and natural selection will remove it -- hence natural selection will tend to prevent evolution.
But a change in the environment (like a mass extinction) will change what is considered "fit" -- it will take the species and plop it right on a new and different graph, not necessarily at a peak. Now there is a direction "up" and variations in morphology that are in this direction will be selected for; we will now see evolutionary change.
This world can take my money and time/ But it sure can't take my soul. -- Joe Ely