Khan Academy Video Misleads on Common Ancestry – Discovery Institute

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With its generally high-quality online content, Khan Academy exercises a remarkable influence on what students and teachers alike learn about science and other subjects. Thats why I have devoted four posts to analyzing the outdated junk science in their video on Evidence for Evolution. After going through supposed lines of evidence fromembryos,homology, andfossil horses, the video ends by looking at biochemical similarities between organisms, presented as a suite of arguments for common ancestry.

Khan claims that How the DNA gets replicated and translated and transcribed is very similar from one life-form to another. Yet a2020 papernoted that the Origin of DNA replication is an enigma because the replicative DNA polymerases (DNAPs) are not homologous among the three domains of life, Bacteria, Archaea, and Eukarya. These differences are so great that one paper asked Did DNA replication evolve twice independently? The paper proposes that the modern-type system for double-stranded DNA replication likely evolved independently in the bacterial and archaeal / eukaryotic lineages. And while were discussing fundamental biomolecular similarities, anotherpapercompared the genomes of 1,000 different prokaryotic organisms and found that of the 1,000 genomes available, not a single protein is conserved across all genomes.

It is of course true that all life uses DNA and proteins. The video argues that this universal similarity across life hints at a common ancestry. True, universal common ancestry is one possible explanation for such biochemical similarities but are there others that go unmentioned by Khan? As we saw withhomology in vertebrate limbs, its key to appreciate functional requirements. Last year Emily Reevesexplainedthat many properties of the amino acids used in life appear optimal for our biochemical needs. So, there are good functional reasons why all life should use these same molecules.

Moreover, because all life-forms use DNA (which contains nucleotides) and proteins (made of amino acids), we are able to gain nutrients we need amino acids and nucleotide bases from the plants, animals, and other organisms that we eat. The fact that all life uses the same basic building blocks is precisely what makes the food web possible! These universally shared similarities might indicate the design of the ecosystem, not common ancestry.

Once we appreciate that there are good functional reasons for life re-using the same basic molecules (e.g., DNA, proteins), common design becomes an alternative explanation. Intelligent agents frequently re-use the same types of parts in different designs to meet functional requirements. Think of how both cars and airplanes use wheels, or how different versions of Microsoft Windows re-use key computer codes. As Paul Nelson and Jonathan Wells observe in the bookDarwinism, Design, and Public Education:

An intelligent cause may reuse or redeploy the same module in different systems, without there necessarily being any material or physical connection between those systems. Even more simply, intelligent causes can generate identical patterns independently. If we suppose that an intelligent designer constructed organisms using a common set of polyfunctional genetic modules just as human designers, for instance, may employ the same transistor or capacitor in a car radio or a computer, devices that are not homologous as artifacts then we can explain why we find the same genes expressed in the development of what are very different organisms.

The Khan Academy video never considers this possibility, but again, common design the intentional re-use of a common blueprint or components is a viable explanation for the widespread functional similarities among the biomolecules found in different types of organisms.

The video then compares humans and chimps, saying that the latters behaviors and facial expressions are eerily human. I could say the same thing about the behavior of my family cat, Bonsai who is very intelligent and often seems able to read my mind and anticipate my behaviors. This doesnt necessarily mean were genetically related it means we were built with minds and mental outlooks that have important overlap. And the fact that our minds and behaviors have important overlap means that we can relate to one another quite well. In fact there are numerous examples of animals within species or across species being able to relate to one another. Just Google animal friend videos and make sure youve got an hour to kill! Heres my point: if the designer is a being that is into relationships, then designing species with mental and emotional similarities that foster inter- or intra-species deep emotional connections and friendships should not come as a surprise. No common ancestry needed.

But that overlap has significant limits. Just like chimpanzees, my cat doesnt use complex language, build complex tools, use fire, wear clothing, engage in abstract reasoning, do math, compose music, write poetry, ponder the mysteries of the universe, practice religion, or engage in any number of advanced cognitive or spiritual activities. (I would say that he doesnt engage in moral reasoning. However, I am pretty sure that he knows there are things I dont want him to do and he deliberately does those things, apparently for that very reason, like when he recently woke me up from a badly-needed nap by crying at my bedroom door. In any case, my cat definitely lacks an appreciation for morality as found in humans.) So, while some basic behaviors link all mammals, there are numerous higher behaviors found only in humans. Somehow these points get left out of the Khan Academy video.

The video then claims that humans and chimps are 98 percent genetically similar, saying their genes show just how close to human beings they actually are. That statistic is false: it overstates human-chimp genetic similarity, as I explained here last year; see, Human-Chimp Similarity: What Is It and What Does It Mean? At that post, I further explained that any given percent genetic similarity between two species does not necessarily imply an ancestral relationship since that similarity could be present for functional reasonsreflecting their common design.

The video closes by saying that the fact that we can measure how far things are away allows us to create a very accurate tree of life. This sounds like the claim I responded to from Richard Dawkins last year that genetics data allow us to create a perfect hierarchy a perfect family tree. Except when you dig into the technical literature you find out this isnt true at all. I also reviewed this evidence last year in response to Dawkins at Phylogenetic Conflict Is Common and the Hierarchy Is Far from Perfect. A very nice treatment of problems with the tree of life is given in Jonathan Wellss sequel to his bookIcons of Evolution,titledZombie Science: More Icons of Evolution. He summarizes there the many problems facing the tree-of-life hypothesis, including:

Perhaps Wellss most relevant point in rebuttal to Khan Academy comes when the video claims that we can easily determine percent genetic similarity between organisms. And then out pops a tree. Heres what Wells writes inZombie Science:

Since the rise of molecular biology in the mid-twentieth century, biologists have increasingly used comparisons of sequences in DNA, RNA and protein to construct phylogenetic trees. For example, a particular DNA sequence might be present in different species, though with minor variations. Comparing the sequence differences in species A, B, and C could lead to an inference that species A is more closely related (that is, more similar) to species B than it is to species C. The similarity between two sequences (often called homology) can be expressed as a percentage, representing how many subunits at corresponding positions are identical between them.

Similarity may be assumed to imply genealogy, but this is only an assumption. Any inference to genealogy based on sequence similarity is hypothetical. And since molecular sequences (with rare exceptions) are available only from living organisms, any inference about the evolutionary past of those organisms-including their ancestors-is even more hypothetical.

This is exactly right. As I haveexplained in the past, the basic logic behind building molecular trees is relatively simple. First, investigators choose a gene, or a suite of genes, found across multiple organisms. Next, those genes are analyzed to determine their nucleotide or amino acid sequences, so the gene sequences of various organisms can then be compared. Finally, an evolutionary tree is constructed based upon the principle that the more similar the nucleotide sequence, the more closely related the species.But the whole process is based upon theassumptionthat genetic similarities between different species necessarily result from common ancestry.But theres no need for that assumption. If the similarities being compared are functional similarities which is always the case when you are comparing gene sequences between organisms then those functional similarities could reflect common design rather than common descent.

The Khan Academy video opens by quoting Theodosius Dobzhansky who famously stated, Nothing in biology makes sense except in the light of evolution. Khan further says that the modern theory of evolution is about as strong as theories get. But when, to make the case for the theory, you have to resort to all these old, long-refuted icons of evolution, how strong is the evidence really? Its worth recalling Jonathan Wellss remarks at the end ofIcons of Evolution:

[T]he claim that nothing in biology makes sense except in the light of evolution is demonstrably false. The icons of evolution are a logical consequence of the dogma that nothing in biology makes sense except in the light of evolution. All the misleading claims we have examined in this book follow from the sort of thinking represented by Dobzhanskys profoundly anti-scientific starting-point. [S]cience at its best pursues the truth. Dobzhansky was dead wrong, and so are those who continue to chant his antiscientific mantra. To a true scientist, nothing in biology makes sense except in the light of evidence.

Wells is correct that when you start with Dobzhanskys dogmatic statement, you get bad science. You also get bad science education. Its very unfortunate that Khan Academy which is so good on so many other subjects is misinforming students about the evidence, or lack of it, for evolution.

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Khan Academy Video Misleads on Common Ancestry - Discovery Institute