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What Do Biologists Really Know About Macroevolution?

American Museum of Natural History
American Museum of Natural History, by Ingfbruno / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0).

When evolutionist Colin Patterson asked at the American Museum of Natural History in 1981, “Can you tell me anything you know about evolution, any one thing, any one thing, that is true?” his colleagues were aghast. Why, the origin of species that leads to macroevolution is an accepted truth! One does not question accepted truths. Of course they knew about evolution! The evidence is everywhere. It’s … here, it’s … there, it’s — well, evolution is a fact, and if the evidence isn’t available today, it will be tomorrow.

A recent paper in Science allows us to hold the magnifying glass up to claims of observable evidence supporting macroevolution. Gustavo Burin et al., in “Macroevolutionary stability predicts interaction patterns of species in seed dispersal networks,” published in the journal Science, use the word macroevolution 32 times. Burin and two colleagues from Brazil studied 468 bird species in 29 seed dispersal networks. From the data, they claimed to see evidence for macroevolution — evidence so secure, it allows them to make predictions about evolution. This should be a good case study. Do they really know about evolution, or is their exercise a detailed construction of a house of cards?

“The Footprint of Evolution”

Two reviewers, Carolina Bello from Switzerland and Elisa Barreto from Brazil, gave their perspective about the paper, also in Science. As evolutionists, they were pleased to see the effort by Burin’s team showing “The footprint of evolution in seed dispersal interactions.” 

The footprint of evolution should be obvious. Fruit-eating (frugivorous) birds eat the fruits with the seeds, then fly away, leaving seeds widely dispersed for the good of the plant. Widespread distribution of favorite plants is also good for the birds. One bird species will often feed on multiple fruits, and plants will often host multiple species of birds. A complex network of bird and plant interactions should result. Over time, the symbiotic relationships should persist even as the players evolve or go extinct. Bello and Barreto use the word macroevolution 7 times in three paragraphs, and yet their piece betrays a persistent undertone of doubt about what Burin et al. showed — indeed, what all such macroevolutionary studies have been able to show. Here are some of the problems they mention:

  1. The effects of evolutionary processes over deep time “are not clear.”
  2. “Understanding how evolutionary dynamics influence species interactions is a challenge that has persisted for a long time,” they admit.
  3. They acknowledge a big difference in the time scales of “observed networks and the macroevolutionary processes.”
  4. Most previous studies have been indirect, focused on “reconstructing trait evolution of the interacting species as a proxy to detect coevolution,”
  5. Burin et al’s method is “still controversial.”
  6. Burin’s team take “a leap” to merge macroevolution with an interaction network.
  7. The rate estimates are uncertain.
  8. The phylogenetic hypothesis uncertain.

Their support for the Burin paper is, in the final analysis, only faint praise: 

Accurately estimating speciation, and particularly extinction rates, from phylogenies composed solely of extant species is still a challenge, making it hard to detect the footprint of evolutionary dynamics on species interactions. [Emphasis added]

After reading the Burin paper, therefore, Bello and Barreto are not entirely sure the authors know what they claim to know.

Into the Weeds

One thing Darwinism has going for it: it sure generates a lot of busy work. But so does constructing a house of cards; whether effort corresponds to knowledge is a separate question. With their 32 mentions of macroevolution, can Burin’s team demonstrate knowledge about it? Even in the case of watching birds eat fruit, is the evidence clear? The authors are offered a fair chance to convince a skeptic as we dive into the text and supplemental materials.

They face challenges at the outset. They cannot watch extinct birds eating fruit, obviously, so what’s up with that? 

Starting from a molecular phylogeny (Fig. 1A), we estimated rates of speciation, extinction, net diversification rate (speciation minus extinction), and extinction fraction (extinction divided by speciation rate) for all species in the networks. We then estimated species’ interaction patterns (how they were connected) within each of the 29 networks (Fig. 1B), using three different network descriptors to characterize interaction patterns of each species, which were then combined into a single descriptor index for each species by using principal component analysis (PCA). We then used a hierarchical Bayesian phylogenetic framework to test for relationships between macroevolutionary stability and interaction patterns of bird species (Fig. 1C).

Circular Reasoning

The circularity of their reasoning escapes them. They assume macroevolution (molecular phylogeny) to learn about macroevolution. They “estimate” speciation rates and extinction rates based on their belief in macroevolution. They place each bird into a network and connect all the assumed data points into a phylogenetic framework. Nowhere do they mention fossils, like finding a fossilized dove eating a fossilized apricot. Essentially, they use evolutionary assumptions to demonstrate facts about macroevolution! Do they know how many species originated, and how many went extinct? No! They only estimate how many must have evolved, based on their Darwinian mindset.

We found that central bird species in seed dispersal networks tend to belong to macroevolutionarily stable lineages. Standardized speciation and extinction rates show, respectively, positive and negative associations with species’ patterns of interaction (Fig. 2A).… Hence, central species are more likely both to persist in time (negative correlation with extinction rate) and to belong to clades that are more likely to provide a replacement species if one goes extinct (correlations with extinction fraction and diversification rate).

This Is Preposterous

Any skeptic of Darwinism would call foul here (no pun intended). One cannot simply assume that evolution will provide new species for ones that bow out by extinction, when they have no fossil evidence that that is what happened. Their powers of suggestion lead them into fantasyland:

This suggests that the macroevolutionary sorting mechanism acts at a regional scale, sorting the species within each region through their relative rank of stability, rather than on absolute values of speciation, extinction, extinction fraction, or net diversification rates. Our results indicate that representatives of important seed-dispersers groups across multiple localities indeed have high relative macroevolutionary stability, as the result of either fast species accumulation (e.g., thraupid genera, such as Tangara and Thraupis) or long-lived lineages (e.g., species of Turdidae). Ecological factors such as species abundance distributions and the presence of invasive species also influence network organization. Unfortunately, the lack of data prevents us from further testing if macroevolutionary consequences to network structure are modulated by those factors.

The paper is built on assumptions .

  • “One important assumption for the higher-level sorting mechanism, which finds support in previous knowledge, is that the replacement species has similar ecological attributes that allow them to perform similar ecological dispersal services.”
  • “We assume that the two rates of each set of models (each of them plus their interaction) affects the likelihood that a given lineage might be evolutionary stable/reliable at long temporal scales.”
  • “Here we assume that body size is a good proxy for ecology, but we note that all species used here consume fruits in their diet (they are the species found in the networks).”

They also used an arguably vacuous measure of “phylogenetic signal” called Pagel’s Lambda, a value between 0 and 1 that infers that species that resemble each other are more closely related. There are obvious exceptions among species with strong sexual dimophism and in cases of alleged convergence.

Phylogenetic correction was used because the network descriptors showed significant phylogenetic signal (mean value for Pagel’s lambda = 0.537 but note that for each tree the corresponding lambda value was used).

Time to Retire

At least one ecologist, Carl Boettiger at UC Berkeley, has argued that it’s time to retire Pagel’s Lambda, because it relies on biological nonsense and doesn’t measure what it claims to measure. Whatever one thinks of its usefulness, it’s a statistic that relies on Darwin’s tree concept, therefore circular.

So Bello and Barreto were right to express doubts. It’s “hard to detect the footprint of evolutionary dynamics on species interactions.” Estimating speciation and extinction rates from extant species “is still a challenge.” Burin et al. took a “leap” to merge macroevolution and interaction networks. Whether they found “a consistent and robust effect, even when accounting for the uncertainty of the rate estimates and the phylogenetic hypothesis,” is in the eye of the beholder, considering all the assumptions, questionable techniques and circular reasoning involved.

And so, in the end, Colin Patterson’s question echoes through the decades: “Can you tell me anything you know about evolution, any one thing, any one thing, that is true?”