First molecular biologist: What’s the difference between a Creationist and a Crustacean?
Second molecular biologist: I don’t know – what is the difference between a Creationist and a Crustacean?
First molecular biologist: Well, it seems you’re in the wrong job, then.
This joke derives pretty closely from a sentence in a thought-provoking 2009 paper, What is the viewpoint of haemoglobin and does it matter by Jonathan Marks, a geneticist and biological anthropologist. His actual words are:
In other words, if you cannot tell a human from a gorilla, you really should not be in biology.
He was commenting on some 1963 research which had suggested that, since there are less than a handful of base differences between human and gorilla haemoglobin, humans must be essentially a sub-variety of gorilla, or vice versa. In reply the celebrated George Gaylord Simpson wrote:
From any point of view other than that properly specified, that is of course nonsense. What the comparison really seems to indicate is that … haemoglobin is a bad choice and has nothing to tell us about affinities, or indeed tells us a lie.
Jonathan Marks adds to this comment:
Does it not stand to reason that if you essentially cannot tell human haemoglobin from gorilla haemoglobin, the sensible thing to do is look at something else? In other words, if you cannot tell a human from a gorilla, you really should not be in biology.
His larger aim in the paper is to point to the more recent equally, and comparably, fallacious conclusion that because human DNA is 98.5% the same as chimp DNA, it means that humans are “really” almost the same as chimps… from which follows, amongst other things, the move to accord human rights to chimps (when, as Marks acidly observes, they haven’t yet been applied to many humans). He states what ought to be obvious:
It is not that difficult to tell a human from an ape, after all. The human is the one walking, talking, sweating, praying, building, reading, trading, crying, dancing, writing, cooking, joking, working, decorating, shaving, driving a car, or playing football. Quite literally, from the top of our head (where the hair is continually growing, unlike gorillas) to the tips of our toes (the stoutest of which is non-opposable), one can tell the human part from the ape part quite readily if one knows what to look for. Our eye-whites, small canine teeth, evaporative heat loss, short arms and long legs, breasts, knees, and of course, our cognitive communication abilities and the productive anatomies of our tongue and throat are all dead giveaways. However, they are not readily apparent in a genetic comparison.
In other words, predicating chimp and human similarity on the apparent similarity of their genomes is like finding rather similar-looking Japanese manuals with your new car and your new camera and assuming that a car must be much the same thing as a camera. It’s a sign that you are losing hold on reality.
As well as describing how it’s easy to be obsessed with genes to the point of missing the “bleedin’ obvious”, Marks writes seriously about how today’s commonest taxonomic tool – cladistics – similarly diverts our attention in its very basis by dealing entirely with similarities, when the main interest of evolutionary theory ought to be differences, and how to account for them. It seems to me that poses questions that are deeper than they first appear.
The general idea that classification systems, which are necessarily based on similarities, tend to hide the need to explain difference, is not restricted to the assumption that if chimp genes and human genes are similar, the species are similar, or that if two taxa are close on a cladogram, we can ignore their divergences. One thing (almost the only thing) I found helpful in the postmodernist Michel Foucault’s book The Order of Things) was his discussion of the Linnean classification system and its various precursors and alternatives. This too highlighted the fact that how we classify things depends entirely on what similarities we choose to make significant in our worldviews.
In a different way of seeing the world, for example, the similarities caused by convergence could be considered more noteworthy than those of descent. A dolphin would be closer to an ichthyosaur than to an artiodactyl. After all, when you’re hiring staff you compare their qualifications, not their parents’ professions or genomes.
But once we turn the coin over and ask, “How do I account for the differences between chimps and man, as opposed to their similarities?” the first step, surely, must be to decide just how different they are: what it is that needs to be explained. In order to ask, “How did chimps become humans?” (or “How did they diverge from a common ancestor?”), you have to ask first “What is a chimp, and what is a human, so that we know what differences need explaining?” The answer has to be, “Everything that isn’t included in the cladogram as a shared character.” The classification is therefore of minimal help for the task.
We need to measure difference, then, not similarity, in some way that is more direct and complete than comparing their haemoglobin or even their genome as proxies. It’s a vital scientific task because, after all, demonstrating common ancestry has little real purpose beyond refuting Special Creationism, whereas evolutionary theory is supposed to explain the origin of the different species.
As I think about this, I begin to sense that “difference” may be rather an intractable scientific problem. At the instinctive level, it’s easy, as Marks’s list of obvious human characters shows. But his list is not in the least exhaustive – and perhaps some of the differences he lists are are not essential. Should the list of differences also include playing music? If so, how is music defined, as opposed to a chimp, perhaps, taking pleasure in the noise of smashing stones together? Is preferring Country and Western to Bach a significant difference, or not?
There is simply no way one can do the job of objectively and scientifically quantifying all the differences even between two closely-related taxa. There is no way of presenting the results in a robust mathematical way that would, for example, tell you that there is 30% more similarity between man and chimp than between chimp and gorilla. There is no way to decide, apart from some entirely subjective and arbitrary list of attributes with scales of magnitude, that since the two species separated, 5X10^4 Tb, rather than 4 tonnes, of differences have resulted, and that is what needs to be accounted for – there isn’t even an SI unit for “difference”.
And yet there can be absolutely no doubt that the differences are objective, unchanging and actually very easy to detect and describe individually. How can it possibly be that one of the most fundamental categories in science – difference – cannot be reduced accurately to scientific expression? What’s wrong with the world?
Now, in the disputes about intelligent design, one of the major critiques is that whilst those like Bill Dembski have developed statistical models to distinguish design from pure chance, these are scientifically useless because necessary categories like “functional information” fight shy of scientifically robust definitions. Instinctively it may seem obvious that organisms as a whole, or the constituent systems thereof, are purposefully designed, but since that design cannot be objectively quantified, design cannot be said to be a scientific category.
But do you see that this is exactly the same situation that exists with the fundamental concept of “difference” between species? There are profound differences between species, as any fule gno. But if those differences cannot be quantified, apart from flawed and incomplete models like genetic comparisons, how can it be considered to be a real constituent of science?
If design must be excluded from science because it cannot be quantified or even exhaustively defined, then so must biological difference, for the same reason. Do we really want to go there? If that logic is valid, then maybe we have to live with giving chimps the vote, and accept madness as the price of scientific progress.
Jon,
You might become a “denier” of evolutionary “science” yet!
You wrote:
“Marks writes seriously about how today’s commonest taxonomic tool – cladistics – similarly diverts our attention in its very basis by dealing entirely with similarities, when the main interest of evolutionary theory ought to be differences, and how to account for them. It seems to me that poses questions that are deeper than they first appear.”
Related to this I think, is that it seems to me that evolutionists try to prove common ancestry using BOTH similarities AND differences. Or maybe ‘similarity of differences’. In any case, it seems like a ‘Heads I win, tails you lose’ thing.
An example from BioLogos:
“1. Genetic Diversity. … So as we go back on the family tree, there are more and more genetic differences between us and our ancestors… That enables us to make a prediction from the amount of genetic diversity between two species about the time since their common ancestor population lived… The calculation from genetic differences gives a figure remarkably close to the estimated value…
2. Genetic “scars”. Just as scars stay on our bodies as reminders of past events, the DNA code contains “scars” and these are passed on from generation to generation. DNA scars result from the deletion or insertion of a block of bases… If we have the same scar as chimpanzees and orangutans, then the deletion or insertion must have occurred before these species diverged into separate populations. If we and chimpanzees have a certain scar but orangutans do not, we can conclude the deletion or insertion must have occurred after the common ancestor of chimps and humans separated from our common ancestor with orangutans. In this way we can create a detailed family tree of common ancestors.
3. Genetic synonyms. … That is exactly what we find among the DNA of humans and chimpanzees: there are many more synonymous differences between the two species than non-synonymous ones. This is exactly what we would expect if the two species had a common ancestor, and so it provides further evidence that humans and chimpanzees were created through common descent from a single ancestral species.”
https://biologos.org/common-questions/human-origins/what-scientific-evidence-do-we-have-about-the-first-humans/
My own opinion is that those markers indeed provide credible evidence for common descent, over against common design without descent, but that says little about the mechanisms involved. Common descent and common design are, after all, not mutually exclusive.
And in any case, all three of those BioLogos points are still primarily concerned with similarity – (1), notably, is really saying, “the closer you get on the family tree, the more similarity.” You could compare that to recognising family resemblances in a photo of your long-lost father, but less in your great-great grandfather, and deciding which is which on that basis.
However, family trees also have to explain descendants, not just ancestors: what happened to your great-great grandfather that made you look different? Why are your third cousins all alcoholic morons when you’re a professor of moral theology? And that, I suggest in the post, is what the main interest of biology ought to be.
“My own opinion is that those markers indeed provide credible evidence for common descent, over against common design without descent…”
I’m wondering what evidence exists which evolutionists would consider NOT credible evidence for common descent. I think they see evidence for their theory in ALL directions. (That was what I was trying to get at in my first post.)
“… Common descent and common design are, after all, not mutually exclusive.”
Would this refer to what might be called Intelligently-Designed Evolution?
Well, I certainly agree that evolutionary theory (talking Neo-Darwinism here specifically) has made itself unfalsifiable (partly because it has so few tightly constrained concepts, which is the link to the post). ANY data can be made to fit ANY theory if you add enough epicycles, but since Darwinism is so law-free and unpredictable anyway, and ideologically loaded to boot, it’s an extreme case.
Yes – “intelligently designed evolution” is broadly what I had in mind – but that covers a wide range of possible bases, from (a) miraculously performed transformations of existing species, through (b) occasional interventions at key points, or (c) Aquinas’s concept of universal providence, and at the other extreme, (d) evolutionary front loading.
I’m open to all those possibilities, though prefer some to others – for example, (d) is irreducibly Deist, and as far as I can see makes creation a shotgun affair, rather than a precision tool.
But the key theological issue is whether God creates all things according to his will. Deny that, and I start baring my teeth. Acknowledge it, and I think the issues are largely scientific, or perhaps philosophical, matters of dispute and therefore realtively minor issues – if indeed answers can be given at all. (This assumes what’s already been discussed at length and isn’t worth raising again – that I don’t believe Genesis gives a literal material account of how).
Cath-
There are many things that would be evidence against common descent. The fact is they have not been observed.
If the animals on islands close to the continents all looked the same, instead of looking more like the animals on the closest continent, that would be evidence against common descent.
If humans cells reproduced using DNA and RNA, and cells of all other organisms used some other system of reproduction, that would be evidence against common descent.
If a surveillance camera showed a herd of something like an antelope popping into existence, that would be evidence against common descent.
If birds’ wings were the same as bats’ wings, to the extent that it appeared that bat wings had been added in one fell swoop to a different animal to make the first birds, that would be evidence against common descent.
Welcome back Walter.
Whilst I don’t disagree with the likelihood of common descent, as I said to Cath above, there ain’t a theory alive that doesn’t have some evidence against it. Maturity as a thinker is in weighing the pros and cons (and accepting that it’s always possible to be wrong).
I don’t place much value on what evidence one can concoct that ought to be there to convince oneself – it smacks of Jerry Coyne’s prescription of a 900 foot high Jesus, Precambrian rabbits and other froth – the evolutionary counterpart to Creationists’ crocoducks. And just as intellectually vacuous. There would be no obligation for the Creator to conform to what we think ought to happen.
If I had to give (off the top of my head) examples of real observations that don’t fit quite so well with common descent, I’d consider (let’s try and match your fictitious examples):
(a) The fact that the presence of some taxa in anomalous localities is only explicable by unlikely transcontinental raft journeys.
(b) The fact that DNA replication, which is both fundamental and complex, appears to have evolved at least twice.
(c) The fact that the vast majority of new forms “pop into existence” in the fossil record and have to be explained theoretically, in the absence of actual transitions.
(d) The fact that there are many cases of convergent evolution of complex molecular and physiological systems that are apparently independent.
One recent (this month!) example of (d) is that the ostrich, whose wings have been widely used as a classic example of vestigial organs, have been found to mimic closely newly discovered feather patterns on the ornithischian Ornithomimus – before feathers were used for flight, so scarcely vestigial! Does that disprove common descent? Of course not, but it does expose rubbish theological arguments disguised as science.
Transcontinental raft journeys even I would not believe. Transoceanic are rare enough!
The fellahs that impress me are the larger pterosaurs, whose distribution suggests they were, essentially, global aerial travellers. 50 foot winsgspan and good land mobility gives one plenty of options.