Lessons From Mammals
by MikeGeneIn his debate with Rick Warren, Sam Harris provides us with the conventional perspective on evolution:
HARRIS: I'm doing my Ph.D. in neuroscience; I'm very close to the literature on evolutionary biology. And the basic point is that evolution by natural selection is random genetic mutation over millions of years in the context of environmental pressure that selects for fitness.
WARREN: Who's doing the selecting?
HARRIS: The environment. You don't have to invoke an intelligent designer to explain the complexity we see.
Harris is correct in noting that we don't have to invoke ID to explain "complexity." I, for example, merely tentatively infer ID because of certain data patterns. But that's another topic. Instead, I'd like to focus on the conventional definition "“ "evolution by natural selection is random genetic mutation over millions of years in the context of environmental pressure that selects for fitness." While I agree this is a valid perspective of evolution, I would suggest the problem is that it is incomplete. That is, it is a superficial perspective on evolution. Perhaps this is why it appears to have misled the scientific community and public.
We have just seen how the conventional view of evolution appears to have gotten it severely wrong on something as fundamental as the origin of mammals.
According to conventional views, dinosaurs had ruled the Earth by soaking up all the good niches. As Krauze explains:
Once upon a time, the world was ruled by the dinosaurs, with mammals being confined to cracks and crevices. But the fortuitous impact of an asteroid caused the dinosaurs to go extinct, paving the way for the advance of mammals and, ultimately, us. That, plus some philosophical bon mots about the randomness of evolution, has been the traditional story of mammalian evolution.
It is important to remember two things for historical record. First, this conventional view quickly became deeply embedded in evolutionary science. In other words, this was not some question of scientific minutia, this was an explanation for the origin of mammals and it became an instant hit, finding its way into countless textbooks and museums.
Second, this view of mammalian origin is a direct product of the conventional view as outlined by Sam Harris. It was a story that highlighted the central roles of contingency and the environment. It was the environment that kept mammals from evolving into anything of significance during the Age of the Dinosaurs and it was again the environment that was behind their massive radiation once dinosaurs went extinct. And what unleashed all this massive environmental pressure? The raw contingency of an asteroid impact. 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.
According to the Bininda-Emonds et al. study (discussed by Krauze), the cornerstones of the conventional theory have been removed, as their study undermines the conventional view from both sides. First, it shows that mammals underwent some rather extensive evolution while the dinosaurs "ruled the Earth"; all of the extant orders of mammals appeared before the dinosaurs went extinct. And as if this isn't bad enough, once the asteroid hit and the dinosaurs went extinct, opening up all sorts of new niches, no massive radiation of new mammalian evolution was triggered; it wasn't until 10 million years later that the mammals began to radiate at the family level. In short, there seems to be a distinct disconnect between mammalian evolution and the environment, clearly indicating that Harris's notion of the environment doing the "selecting" is a superficial perspective on evolution.
We are now left with the following pattern. Egg-laying mammals split off the rest about 166 million years ago. Then, about twenty million years later, marsupials split from placentals. Nothing much happened for about 50 million years, then over the next 20 million years or so, all of the extant orders of mammals had evolved. Ten million years later, the asteroid hits and the dinosaurs go extinct. Ten million years later, the mammals again begin to significantly diversify over a period of 40 million years.
The challenge for the conventional view is to come up with environmental pressures at these key points, while explaining why the environmental changes associated with a global catastrophe and global-wide die-off seemed to have no effect. The alternative is to hypothesize that environmental pressures are secondary evolution forces that are more important in small-scale acts of fine-tuning. That is, the truly interesting evolution may emerge from factors that are intrinsic to life.
April 7th, 2007 at 10:10 am
What indicators would point to factors that are intrinsic to life and are you able to correlate them to critical events in time i.e. divergences, major environmental events etc.?
Comment by Bradford — April 7, 2007 @ 10:10 am
April 7th, 2007 at 10:39 am
Excellent question (hinting of yet another positive way to express an ID view). But I'm a one-step-at-a-time kind of guy. It's important to take the moment and appreciate the shift. The conventional view has long dominated and influenced perception of evolution, but here is yet another example where it has misled people. It is often said that there is a robust Theory of Evolution. If there is such a Theory, how do you get such a huge mistake as this? Perhaps it's best right now for everyone to admit that no one really knows how mammals evolved. Random mutations and natural selection were part of the story, but that's about all we can say. And the trend is moving toward leveling off the playing field between intrinsic factors and environmental influences.
Comment by MikeGene — April 7, 2007 @ 10:39 am
April 7th, 2007 at 11:39 am
I wouldn't dismiss the importance of environmental influences quite so easily. Remember, the Bininda-Emonds et al. study is a *molecular* study of *extant* mammals. It is very hard to calibrate molecular clocks, and this new phylogeny is not the last word. But more important, if you look at the fossil record, there *is* a big spike in speciation just after the K-T boundary. Many of the species that evolved then have gone extinct since.
Here's a good read on that:
http://gregladen.com/wordpress/?p=594
But I agree that the Bininda-Emonds et al. study does raise all kinds of interesting new questions regarding the (environmental or otherwise) causes of mammalian evolution.
What sort of intrinsic factors are you thinking of specifically?
Comment by Raevmo — April 7, 2007 @ 11:39 am
April 7th, 2007 at 12:04 pm
Who provided the environment?
Comment by AnaxagorasRules — April 7, 2007 @ 12:04 pm
April 7th, 2007 at 12:14 pm
I agree with Raevmo. The fossils seem to be telling a different story than the molecular study based on extant groups. My guess is a lot of work will be be necessary–both with fossil finds, paleoecological studies and further molecular work– to bring all the lines of evidence together so that we can get a better picture. But I don't expect anything overturning the basic principle of adaptive radiations requiring ecological opportunity.
Comment by KC — April 7, 2007 @ 12:14 pm
April 7th, 2007 at 1:23 pm
KC:
There is a secondary consideration within the ecological opportunity perspective namely, are observed outcomes completely aligned within opportunity realizations? If there are difficulties here then there is room for the additional theoretical constructs that MG might have in mind.
Comment by Bradford — April 7, 2007 @ 1:23 pm
April 7th, 2007 at 4:16 pm
KC wrote:
How do the fossils tell a different story?
Comment by Guts — April 7, 2007 @ 4:16 pm
April 7th, 2007 at 5:39 pm
Guts writes:
The fossils suggest the adaptive radiation of the modern mammalian familes began in the Paleocene (right after the K/T boundary), as opposed to the Eocene or later, as suggested by the Nature paper.
Comment by KC — April 7, 2007 @ 5:39 pm
April 7th, 2007 at 6:11 pm
Mike Gene wrote:
[Emphases added]
What is contingency?
In previous comments I've alluded to the ambiguity of this concept.
To say of an event that it is contingent in no way favors the notion that it happened by 'chance' over the notion that it happened by the free choice of a rational agent.
Comment by stunney — April 7, 2007 @ 6:11 pm
April 7th, 2007 at 7:33 pm
KC wrote:
Do you have a reference?
Comment by Guts — April 7, 2007 @ 7:33 pm
April 7th, 2007 at 8:48 pm
Guts:
Follow the link I gave above.
Comment by Raevmo — April 7, 2007 @ 8:48 pm
April 7th, 2007 at 10:37 pm
You know, you'd have a lot more credibility as non-creationists if you'd drop their nasty habit of claiming that every new bit of information makes all scientific thought prior to that point, in error.
If the Chixculub object did not by itself cause the demise of dinosaurs, and the evidence has been very hard for at least a decade that it was not the sole cause, that doesn't affect the validity of evolution theory (by natural and sexual selection) in the least. If mammals radiated prior to the event, that doesn't mean evolution is in error. It only means that the object's strike was not the sole cause.
Creationists like to seize upon any snippet of data that might be misconstrued as a problem for evolution theory, and prematurely pronounce evolution dead. Just like you did here, MG.
If you have the data against evolution, publish it. If you don't, go to the lab or to the field and report on what you find.
But please, don't walk like a creationist, quack like a creationists, lay creationist eggs, and then claim to be apart from creationists.
Comment by edarrell — April 7, 2007 @ 10:37 pm
April 7th, 2007 at 11:11 pm
Mammals *do* radiate dramatically right after the K-T boundary 65 million years ago; what the new study showed with a supertree analysis is merely that those mammals were not primarily within the major mammalian crown groups, which, and this is extremely important to keep clear, are *arbitrarily* defined and delimited by whatever species just happen to be living right now, in the present, at 0 million years ago. So most of MG's post is wrong.
Comment by nickmatzke — April 7, 2007 @ 11:11 pm
April 7th, 2007 at 11:26 pm
edarrell:
MG has not maintained that "evolution is in error" if by that you mean MG infers that descent did not occur. His post addresses mammalian evolution and questions orthodox views about it. Neither is he "claiming that every new bit of information makes all scientific thought prior to that point, in error." Your comments are an absurd overreaction.
Comment by Bradford — April 7, 2007 @ 11:26 pm
April 7th, 2007 at 11:41 pm
Nick, kindly elaborate on what you wrote with regard to that quote.
Comment by Bradford — April 7, 2007 @ 11:41 pm
April 8th, 2007 at 12:37 am
Here's a nice summary of the basic findings.
Comment by MikeGene — April 8, 2007 @ 12:37 am
April 8th, 2007 at 1:15 am
Nick is correct. The Nature paper was talking about evolution in the crown lineages, not mammals in general. When we look at mammals in general, however, Raevmo's link has anothjer link to John Alroy's Smithsonian monograph, which states quite clearly:
Alroy also states:
This contradicts what Mike wrote:
Comment by KC — April 8, 2007 @ 1:15 am
April 8th, 2007 at 1:19 am
BTW… when I said Nick was correct, that also meant I was wrong too– the
paper was only talking about evolution in extant lineages, so the fossil record does not contradict the paper at all.
Comment by KC — April 8, 2007 @ 1:19 am
April 8th, 2007 at 9:45 am
Hi KC,
Yes, my sentence was poorly written and, as stated, was wrong. But its mostly a nitpick. I provided a nice summary article that states this particular point more clearly:
Laden also offers a good point:
Comment by MikeGene — April 8, 2007 @ 9:45 am
April 8th, 2007 at 11:55 am
Hi Mike,
I agree with Laden, especially where he says coming up with hypotheses (even if later proven wrong) is how science works. What I fail to see, however, is the basic point of your thread here. First of all, the
paper doesn't show that the entire set of conventional thinking about the rise of the mammals is 'severely' wrong. As Reaevmo'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. We can get increasingly nuanced models, sure, as more data comes in. But more nunace doesnlt mean complete revamping, and I don't think there need to be any major revisions yet. I fail to see anything in the
paper contradicting the hypothesis that the elimination of the dinosaurs provided an ecological opportunity which mammals who survived the mass extinction at the K/T boundary were able to exploit.
Comment by KC — April 8, 2007 @ 11:55 am
April 8th, 2007 at 11:59 am
Sigh… I really should use the preview button more…(I dont see any 'edit this' feature when I post). Here's how my previous post should have looked:
Hi Mike,
I agree with Laden, especially where he says coming up with hypotheses (even if later proven wrong) is how science works. 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. 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. We can get increasingly nuanced models, sure, as more data comes in. But more nunace doesnlt mean complete revamping, and I don't think there need to be any major revisions yet. I fail to see anything in the Nature paper contradicting the hypothesis that the elimination of the dinosaurs provided an ecological opportunity which mammals who survived the mass extinction at the K/T boundary were able to exploit.
Comment by KC — April 8, 2007 @ 11:59 am
April 8th, 2007 at 12:23 pm
KC:
You and others may be reading the same words and be hearing different meanings. For example, Krauze:
What are you thinking when he writes that mammals were thought to be "confined to cracks and crevices" Or what significance do you attach to this:
or this:
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?
Comment by Bradford — April 8, 2007 @ 12:23 pm
April 8th, 2007 at 5:54 pm
KC wrote:
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.
Comment by Guts — April 8, 2007 @ 5:54 pm
April 8th, 2007 at 6:55 pm
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:
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.
Comment by Raevmo — April 8, 2007 @ 6:55 pm
April 8th, 2007 at 7:00 pm
Raevmo wrote:
Thats what I wrote here:
You're just repeating what I said.
Raevmo:
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.
Comment by Guts — April 8, 2007 @ 7:00 pm
April 8th, 2007 at 7:26 pm
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?
Comment by Raevmo — April 8, 2007 @ 7:26 pm
April 8th, 2007 at 7:36 pm
Raevmo:
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:
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.
Comment by Guts — April 8, 2007 @ 7:36 pm
April 8th, 2007 at 7:53 pm
I don't follow. "as expected", based on what argument? What are those intrinsic factors?
Comment by Raevmo — April 8, 2007 @ 7:53 pm
April 9th, 2007 at 12:29 am
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.
Comment by nickmatzke — April 9, 2007 @ 12:29 am
April 9th, 2007 at 1:59 am
Hi Raevmo,
"What is the MG/K hypothesis exactly?"
Guts probably means "the Mike Gene/Krauze hypothesis", i.e. front-loading.
Comment by Krauze — April 9, 2007 @ 1:59 am
April 9th, 2007 at 9:31 am
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.
How do know it was "very like just another routine speciation event"?
Comment by MikeGene — April 9, 2007 @ 9:31 am
April 9th, 2007 at 12:31 pm
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?
Comment by chunkdz — April 9, 2007 @ 12:31 pm