Um"¦you really don't understand macroevolution, do you. There is no reason to think that these divergence events were dramatic when they happened. – Matzke

He didn't assert that they were dramatic. To the contrary, I think his point was that if dramatic events don't have the predicted effect on macroevolution, how can Harris assert that less transient environmental pressure can have similarly predictable effects on macroevolution.

In other words, the "rigorous" theory of evolution is about as rigorous as a wet noodle. If you can't even get the seemingly obvious predictions right, how can you expect to make the more "risky" Popperian predictions that would make the theory truly rigorous?

What I fail to see, however, is the basic point of your thread here. First of all, the Nature paper doesn't show that the entire set of conventional thinking about the rise of the mammals is 'severely' wrong.

Hi KC,

I'm certainly no expert on mammalian evolution. On the contrary, I bought into the conventional story of some limited, primitive shrew-like critters surviving in the cracks of the niche-continuum because the dinosaurs "ruled the Earth." Then, when the asteroid hit, it opened up all those niches and the primitive generalist was able to evolve in an explosion of adaptive radiation, thus explaining all the significant mammalian evolution. Thus, from my end, these developments (as nicely communicated in the NYT article) are fairly radical. The "basic point" is that the conventional story was the perfect expression of the conventional view (succinctly explained by Harris) and that this perspective may very well be incomplete.

Hi Raevmo,

I think you may have over-reacted. First, I don't dismiss the importance of environmental influences; I question whether they are always the primary consideration. Second, there is no "thinly veiled attempt to discredit evolutionary scientists as dogmatic"; there is an attempt to communicate that we don't quite as well understand how evolution works as many think. Third, what I considered to be "all wrong" was the conventional story that I embraced. Fourth, I don't claim to know the intrinsic factors that generated mammalian evolution. I happen to think that organisms are not necessarily passive players in their own evolution, simply being acted upon by environmental pressures.

Finally Raevmo, you argue that you are looking forward to the follow-up studies. But why not use current theory to come up with a falsifiable prediction? Why not say, "according to conventional views (as outlined by Harris), I predict the study's estimates to be over-turned and the original story to be re-established?"

Hi eddarell,

You are engaged in a knee-jerk reaction. There is no denial of common descent. And arguing that the conventional view is incomplete is not the same as arguing it is invalid.

Hi Nick,

I'm not sure anyone truly "understands" macroevolution and how it plays out. In fact, it is my view that we have a lot more to learn and understand about it.

There is no reason to think that these divergence events were dramatic when they happened. E.g., when the lineage that gave rise to the modern egg-laying mammals split from the lineage that gave rise to placentals, **this was very likely just another routine speciation event**.

How do know it was "very like just another routine speciation event"?

"What is the MG/K hypothesis exactly?"

Guts probably means "the Mike Gene/Krauze hypothesis", i.e. front-loading.

Where were the environmental pressures associated with:

Egg-laying mammals splitting about 166 million years ago, marsupials splitting from placentals 20 million years later, a 50 million years lull, then during the next 20 million years or so the evolution of the extant orders of mammals occurs and then the asteroid hits. Where are the environmental links corresponding to these events?

Um…you really don't understand macroevolution, do you. There is no reason to think that these divergence events were dramatic when they happened. E.g., when the lineage that gave rise to the modern egg-laying mammals split from the lineage that gave rise to placentals, **this was very likely just another routine speciation event**. Both of the daughter species in all liklihood were egg-laying species. All that happened is that, much **later** after the split, one of those lineages lost the egg-laying trait.

You are attributing features of the crown group (modern placental mammals and their common ancestor) with features of the stem group (the lineage that split off from monotremes). The mistake is akin to saying that the first species to split off from the chimp lineage had the features of modern humans. But there were tens of millions of years of evolution between the beginning of the stem "proto-placentals" and the beginning of the crown placentals.

Also: everyone is confusing processes here. Extinction is just as important as speciation in producing the extant crown groups. If multituberculates were alive today, they would be a crown group. But the reasons multituberculates went extinct have nothing to do with the K-T event, because they went extinct tens of millions of years later.

Those groups that relied on such a contigent event to diversify eventually died off, as expected. Those that were surviving on primary evolutionary factors (i.e. intrinsic factors) continued as normal.

I don't follow. "as expected", based on what argument? What are those intrinsic factors?

I do disagree with Mike's jumping to conclusions and I'm just not that confident as you appear to be in the accuracy of the study's estimates. Anyway, I'm looking forward to the follow-up studies.

Those groups that relied on such a contigent event to diversify eventually died off, as expected. Those that were surviving on primary evolutionary factors (i.e. intrinsic factors) continued as normal.

By the way, I don't see anyone in this thread asserting things matter of factly,no one is jumping to any conclusion with any certainty, we're all just talking about what the data suggests, including Mike I would guess.

Raevmo:

What is the MG/K hypothesis exactly?

I find it strange that you would jump to the conclusion so quickly that Mike is wrong based on ignorance, but are more hesitant to jump to conclusions despite the availability of empirical data.

Raevmo, the nature study shows mammalian diversication, but that when it came to the most important mammalian groups (extant ones) , the KT event was largely irrelevant. They can correct me if I'm wrong, but this is clearly predicted by the MG/K hypothesis. I'll compare you're summary at the end with what the paper did shortly, don't have it on this computer at the moment.

I don't disagree with you that the study suggests that the "more important" extant mammals were largely unaffected by KT. I do disagree with Mike's jumping to conclusions and I'm just not that confident as you appear to be in the accuracy of the study's estimates. Anyway, I'm looking forward to the follow-up studies.

What is the MG/K hypothesis exactly?

Yes, but there *was* dramatic radiation of mammals *that existed at the time* (mostly extinct now) after the KT event. Look at the graphs here (also shown in link I provided before):

Thats what I wrote here:

The subsidiary analysis (Fig 2c) in the study Mike links to shows that it was now extinct groups of mammals that seemed to benefit instead, things like multituberculates or plesiadapiforms. mammals did indeed show a rise in diversity immediately post-KT, but just not the mammals we have around us today.

You're just repeating what I said.

Raevmo:

So it would be a bit premature to conclude from the Nature study alone that the KT event did not cause mammalian adaptive radiation, or more generally that environmental changes are not important in driving such radiations.

Raevmo, the nature study does show mammalian diversication, but that when it came to the most important mammalian groups (extant ones) , the KT event was largely irrelevant. They can correct me if I'm wrong, but this is clearly predicted by the MG/K hypothesis. I'll compare you're summary at the end with what the paper did shortly, don't have it on this computer at the moment.

What the study indicates is that present-day mammals, and by this the study simply means the mammalian groups we see today like carnivores and rodents, were largely unaffected by the KT mass extinction event, one way or another. The net diversification rate of these groups was unchanged going across the boundary, indicating that they were neither hit hard by the event nor did they benefit from other things going extinct at the time.

Yes, but there *was* dramatic radiation of mammals *that existed at the time* (mostly extinct now) after the KT event. Look at the graphs here (also shown in link I provided before):

http://www.nceas.ucsb.edu/~alroy/Paleocene.html

So it would be a bit premature to conclude from the Nature study alone that the KT event did not cause mammalian adaptive radiation, or more generally that environmental changes are not important in driving such radiations.

My take is that Mike was simply making a thinly veiled attempt to discredit evolutionary scientists as dogmatic, in order to make the views he subscribes to look better:

This is a story that was both scripted by the conventional view and then was used to support the conventional view. In essence, scientists saw what they expected to see. This was a story that appeared to be strongly supported by "the evidence."

But it now appears it was all wrong.

The fossil evidence clearly shows it was not "all wrong".

On a more technical note: the molecular study relied heavily on the estimate of 166 My for the splitting off of egg-laying mammals. That's a *minimum* estimate based on the oldest known fossils. If the splitting-off occured 200My ago (as some paleontologists argue), the molecular clocks would have to be recalibrated and the massive radiation of extant mammals estimated to have occurred 10My after the KT event according to this study might well have occurred much closer to the KT event.

I'm still looking forward to reading Mike's view on the "intrinsic factors" of life that contributed to mammalian diversification.

As Raevmo's link to Alroy's paper shows, we have to explain a massive die-off of species (even the the mammals lost 2/3 of their species right around the K/T boundary) and an explosion of diversity right after that"“ the most important radiation in mammalian history"“ that coincides with the extinction of the dinosaurs as a group.

The subsidiary analysis (Fig 2c) in the study Mike links to shows that it was now extinct groups of mammals that seemed to benefit instead, things like multituberculates or plesiadapiforms. mammals did indeed show a rise in diversity immediately post-KT, but just not the mammals we have around us today.

What the study indicates is that present-day mammals were largely unaffected by the KT mass extinction event, one way or another. The net diversification rate of these groups was unchanged going across the boundary, indicating that they were neither hit hard by the event nor did they benefit from other things going extinct at the time.