Bechly's "Species Pairs" Challenge Continued

This topic has been mentioned before, here (then here) and here. I missed this the first time around, but I would like to provide my own answer to Günter Bechly’s ‘Species Pairs’ challenge

To Recap:

The ‘challenge’ concerns the numerous extant species pairs which still look very much alike (given several examples), despite the fact that many have diverged from a common ancestor in a similar or a much longer time frame of ~5 million years that whales took to evolve from land mammals (e.g. Indohyus) to a fully marine organisms (e.g. Basilosaurus). Apparently, Bechly thinks that after divergence, species should readily evolve drastic differences - new body plans as he puts it - but they do not, and this is a problem according to him.

Having made my case, I here formally and publicly pose the challenge again to prove me wrong. My dear Darwinist friends and colleagues, please find in the vast database of 97,000 species at just a single example of any pair of different species that have diverged about 5 million years ago (give or take a few million years) according to a consensus of multiple molecular clock studies, and that exhibit a morphological disparity in their body plans comparable to, say, Pakicetus and Basilosaurus.

My Answer:

Plant Biologist Arthur Hunt has already given a good example from plants, but I want to provide the following example from animals:

TOP: Tiger salamander (Ambystoma tigrinum) - BOTTOM Axolotl (Ambystoma mexicanum)

These two organisms diverged about 5.6 to 11.0 million years ago according to Similar to the time frame of human and chimp divergence. Unless Bechly wants to split hairs over his criterium of “5 million years ago (give or take a few million years)” I think this example counts regarding the time criteria. Regarding the morphological disparity, apart from the superficial color schemes, one is terrestrial and breathes air with lungs, while the other is fully aquatic and even has gills as adults. In some aspects, this is even more drastic than whale evolution (as whales continued to breathe air even today).

Potential Responses:

Although, I expect the main objection against this example to be a complaint that differences are not “drastic enough”. This is actually an issue of the challenge itself - the criteria are rather ambiguous. “Comparable to X” doesn’t really suffice. The ambiguity of the challenge allows one to add new criteria in the future in order to reject answers by simply saying “this doesn’t count since it doesn’t have X, Y, and Z” (even though X, Y and Z were not mentioned before when the challenge was first made). It’s also a bit weird to see DI use ‘body plan’ so liberally. He doesn’t define what he means by that, but he says that whale evolution is a change of body plan. But if you ask Bechly’s colleague Stephen Meyer, a body plan is the shared morphological unity of a phylum. So depending on the criteria, most of Bechly’s own examples don’t count as changes of body plans. Again, the ambiguity of the terms allows one to simply state “this is not a change in body plan”, and make up new criteria on the spot to reject every example that can be potentially given. I.e. the goal post is free to move constantly. I can also anticipate objections to the effect of saying that “this is a loss of information, you need to show new information”. In this case, 1) here the criteria for what would count as “new information” remains similarly ambiguous, and 2) that has nothing to do with the challenge as was originally stated (again, allowing for moving the goal post).

NOTE: After writing that above, I read Bechly’s response to the previous answers provided on this forum. He does exactly what I expected as he rejects Arthur Hunt’s Hawaiian Silversword example, by saying that the differences among the species of Hawaiian Silverswords are all related to different growth forms and allometric shifts of already existing structures. Even though the differences appear superficially striking, they do not involve any novel body plans (i.e., no new proteins, new tissues, or new organs). Notice that this is the first time he has mentioned ‘new proteins, tissues, organs’ as criteria for what counts as a ‘new body plan’. Hilariously, these new criteria may even invalidate his very own whale example (what new proteins, tissues and organs does he think Basilosaurus possessed, while Pakicetus did not?) Funny enough, at the end of the blog post, Bechly exhibits a level of self-awareness when he asserts that his rejections are “neither moving the goalposts nor committing the “no true Scotsman” fallacy”. However, goalpost shifting and no-true-Scotsman are characterized as means to invalidate answers by changing the rules and definitions in an ad-hoc fashion… which is precisely what Bechly did here.

But regardless of all that…

The challenge is erroneous:

Bechly comits some egregious mistakes in the premises he lays out for his challenge against evolution (some already pointed out before). Like when he describes how long it took for whales to evolve from fully terrestrial to fully aquatic.

The fossil record shows that the transition from quadrupedal whale ancestors similar to Raoellidae (such as Indohyus) and Pakicetidae to fully marine pelagicete whales like Basilosauridae happened in just 4.5 million years. This implies that the body plan transition from a pig-like animal to a dolphin-like animal happened within the lifespan of a single species.

He gets this date by taking the age of the first fully marine cetacean and subtracting it from the age of the most recent terrestrial. However, making this calculation to estimate the time it took for this transition to occur is specious, since (in all likelihood) none of these species are direct ancestors/descendants of each other. Weirdly, Bechly acknowledge that they not ancestor-descendent lineages, but he fails to see why this invalidates the reasoning behind his 4.5 million year figure. Cousins only constrain the minimum age for divergences, not the maximum, e.g. the last common ancestor between Pakicetidae and fully marine cetaceans could’ve been much older. This means that the transition from fully terrestrial to fully aquatic organisms could have started much earlier, and may have made a lot of “progress” (not in the Orthogenic sense) by the time when the family members of Pakicetidae or even Raoellidae were around. Thus, subtracting the ages of fossil cousins may underestimate the actual time it took for the transitions to have happened. (For more, see here).

Furthermore, Bechly started the original post by saying that he wants to introduce a fresh new argument into the discourse. However, in my opinion, this is not much different from the Living Fossil argument. The latter is asking “why hasn’t this species changed for millions of years, while others have” while the former asks “why hasn’t this species changed THAT MUCH for millions of years, while others have”. These two are based on the same faulty premise, that we should expect to see similar morphological evolutionary rates in different lineages.

Bechly proclaims that…

There is no conceivable reason why a disparity like that between Pakicetus and Basilosaurus should be limited to the fossil record, where it can be found in numerous examples among all groups of organisms, while being totally absent among the millions of recent species.

Even assuming that there is no such change observed in extant species, this is appealing to personal incredulity. Although, he has made the following probability argument for why we should observe such disparity today, based on two “indisputable” facts.

1.) There are many examples of fossil species pairs with very different body plans that diverged within a window of time of 5 (±5) million years. This is even more remarkable if we consider that there are only about 350,000 described fossil species, which represent only a tiny fraction of the estimated 5-50 billion species that have ever lived on Earth.

2.) There exist no living species pairs with even remotely similar differences in body plan that are dated to have diverged in a similar time frame. This is even more remarkable if we consider that there are an estimated 8.7 million living species, of which more than 2 million are described. Previous estimates of the total number of living species varied from 3-100 million species, but if microbes are included, it could even be up to a trillion living species.

Considering the fact that windows of time of only 5-10 million years account for most of the abrupt appearances of new body plans in the fossil record, the Bayesian likelihood of not finding a single example of similar morphological disparity having originated on a similar time frame among the millions of living species is basically close to zero. I consider this simple argument as a final nail in the coffin of Darwinian unguided evolution.

This argument basically says that, given the numerous “fast evolutionary transitions” (FATs) observed in the fossil record, then by basic probability we should expect to see a similar FAT rate to have happened among the millions of extant species. Even taking the premises for granted, Bechy’s reasoning here is horribly flawed. He is looking at the number of FATs that has occurred in the past ~4.000 million years and wonders why we don’t see a similar number of FATs occurring in the last ~10 million years. I don’t see why that would be surprising, even assuming (which I don’t) that FATs occur at the same rate across all time. He draws specific attention to the numbers of 350,000 described species from the fossil record, and how remarkable it is that we find many FATs among them but not among the millions/trillions of described/estimated extant species. Almost like he is calculating the probability by dividing the number of FATs in the fossil record with the number of 350.000 described fossil species, and then multiplying by the number of extant species to calculate number of FATs we expect to observe in extant organisms. Do I really have to point out why this is erroneous?? The 350.000 species is a SAMPLE of >>99.9% of all species that have ever lived, while extant extant represent the remainder <<0.1%. Again, I don’t see why that would be surprising, even assuming (which I don’t) that FATs occur at the same rate across all time.

To make the error as apparent as I can, I would like to re-state his “indisputable” facts as such:

1.) There are many examples of relatively fast evolution transitions with changes in body plans in the fossil record, i.e. >>99.9% of life’s history and diversity.

2.) Similar evolutionary changes are extremely rare to non-existent among extant organisms, i.e. <<0.1% of life’s history and diversity.

Even assuming such evolutionary changes have occurred at similar rates across all life at all times, this is not surprising.

Question for anyone reading this: Is this an example of the Gambler’s Fallacy? At first I thought so, but now I am not so sure. I still think it is fallacious reasoning regardless.



Just a heads up:
I accidentally published this post before I was finished writing.
Thus, you may have read a post that was not complete yet, but now it’s done.

1 Like

How does he know that these two whales have changes in “basic body plan” and have new proteins, new tissues, and new organs? Exactly what impartial committee have Bechly and you agreed upon to judge what constitutes a basic body plan and to assess the arguments about proteins and tissues? This is like one of those challenges where someone says they will give you $100,000 if you can change their mind.


Not really - the gambler’s fallacy is the expectation that future events will be different from past events, so as to restore the expected distribution (e.g. “we haven’t rolled six for a while, so it must happen soon”).

Bechly is expecting that current events will be the same as those in the past[1], not different, and he doesn’t have an independent probability distribution to compare to, or even any reason why current events should be the similar to past ones.[2]

So whatever fallacy he’s committing, it’s not the gambler’s fallacy.

  1. Though as you note, he’s comparing events across half a billion years to events in a few million. ↩︎

  2. The events he is describing involve radiation of species to fill empty ecological niches, but we are neither recovering from a mass extinction nor seeing new niches opening up. ↩︎


A man came up to me and said
"I’d like to change your mind
By hitting it with a rock, " he said,
“Though I am not unkind.”
We laughed at his little joke
And then I happily walked away
And hit my head on the wall of the jail
Where the two of us live today.

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