Peter K. Dearden
I shout at the television a lot. Natural history programmes annoy me by presenting pat just-so stories about evolution, and Myth Busters drive me nuts with their inability to recognise a fair test. But it is not often that there is a programme about genetics, or one that makes me quite so disappointed.
The programme that currently annoys me is “Dead Famous DNA” here in NZ on the History Channel, but originally a U.K. Channel 4 series. The idea is that the presenter, Mark Evans, wanders the world searching for body parts of famous dead people, extracts DNA from them, sequences their genomes, and then uses that information to diagnose them, explain their characteristics, or understand their ancestry.
In the episode I saw, Dr. Mark, purchased (at pretty hefty prices) bits of bodies claimed to be from Charles Darwin, Marilyn Munroe, John F. Kennedy, Adolf Hitler and Eva Braun, and tried to sequence their genomes to find out ‘stuff’. He also got DNA from someone who claimed to be Elvis’s son, and compared his DNA to the alleged genome of Elvis, which he had sequenced from hair (I think) in a previous episode. Thrilling stuff.
Lets examine, for a moment, the biggest issue with this programme – the attribution of bodily bits. How do you know that the bits you purchased really come from the people you are told they are from, especially when you are paying considerable amounts of cash to get them? If Dr. Mark is listening, for a price, I can provide you with the fingernails of Faraday, the clavicles of Julius Caesar, and the hips of Homer, though you, Dear Reader, might think I am making sh*t up. Dr. Mark acquires bits of burnt bone, from nefarious sources, that may or may not be from Hitler, and then seems to think an anthropologist saying they are from a human, they have been burnt with flesh on and that they are big (therefore male) is some sort of confirmation that it is Hitler. Can I just say I don’t know anyone prepared to sex a skeleton on the basis of one bit of rib, also that not many people are burnt with their flesh off, and that even fraudsters can get bits of humans. It’s a bit of burnt human bone, which someone gave to you, with little attribution, for a pile of cash. Chances are it’s not Hitler!
The attribution problem gets beyond ludicrous when Dr. Mark shows that a man whose mother claimed was Elvis’s son has, by the magic of genetics, no chance to be Elvis son. Except the DNA claimed to be Elvis’s appears to have come from another poorly provenanced bit of hair – might be Elvis, might not. As an aside, hair doesn’t contain DNA unless it has the roots. If this is cut Elvis hair, it won’t have a lot of DNA in it. The ‘scientists’ suggest that the genome sequence from possibly Elvis’s was one of the best they ever had- suggesting to me that it is modern contamination. So we can’t be sure if it is Elvis’s hair, or even if the genome sequence from it is from the hair itself that might not be Elvis’s. So Dr. Mark has conclusively proved that two people (one of whom is probably not Elvis) are unrelated.
But this is not the bit that really rips my undies. The genetics they talk about is misrepresented and silly. Dr. Mark claims that he could use the genome of Marilyn Munroe to work out why she was so beautiful. As a practicing geneticist (I’ll get good one day!) I have no clue how you might do that. Genomes are huge, and most traits, like beauty, involve influences from lots of genes. It is really hard to identify these genes in humans because you need huge numbers of people in your experiment to have the statistical power to find those bits of the genome that have real influence on the trait you are interested in. With hundreds of thousands of people needed, it is unlikely that any studies (and I have looked) would be carried out to identify the hundreds of genes that control such a subjective thing as beauty. So how does the genome of (possibly) Marilyn Munroe tell you anything about beauty when you have nothing to compare it with?
The worst bit was when Dr. Mark diagnosed Charles Darwin with Crohn’s disease. Charles Darwin had an illness that affected the later parts of his life, which had symptoms a bit like Crohn’s, but has been suggested to be all kinds of things including Chagas disease, or even psychosomatic. Dr. Mark tells us that Charles’ DNA shows markers, especially one on chromosome 16, that indicate that he had Crohn’s. O.K. *sigh* Yes, there is a gene variant on chromosome 16, labeled as Inflammatory Bowel Disease 1 (near a gene called nod2), which increases your risk for Crohn’s disease. Different studies indicate different degrees of influence on the disease, and yes, I would say that there is a major gene on chromosome 16 that contributes to susceptibility for Crohn’s disease. But you CAN’T SAY that having that mutation GIVE’s you the disease. You CAN’T SAY that if you have that mutation YOU WILL HAVE Crohn’s disease. It is one of many genes that build a genetic background that is slightly more susceptible to this disease.
This is the key misunderstanding for most diseases or traits like beauty. There is not a one to one correspondence between gene and trait. There is NO GENE for Crohn’s disease, just as there is no gene for beauty, or intelligence. In a vanishingly small proportion of traits one gene does exist, but for most traits it is far more complex, and importantly, we are still trying to work out how to even study them. Dr. Mark’s programme, apart from being arrant nonsense, is the worst kind of pseudoscience; dressed up in a white coat of assurance, it misrepresents and confuses modern genetics. For shame Dr. Mark, you could still have made an interesting program without resorting to telling fibs.
When it comes down to it, I have another problem. People should be judged by their legacy. The legacy of Darwin is in his writing and ideas. The legacy of Shakespeare is in his sonnets and plays. You will not find the ideas of Darwin, the metaphors of Shakespeare or the notes of Mozart, in the sequences of their genomes. Next time Dr. Mark is on, pick up your copy of ‘On the Origin of Species’, skip the bits about pigeons, and read the last paragraphs. That’s Darwin.