I commented on the "throwback family" a few days ago, well, The Times (of London) has two articles which reduce the likelihood of this being a hoax in my mind. It seems clear that there is a family, highly inbred, which lives in Turkey where a number of the children walk on all fours and exhibit other forms of impairment.
Nevertheless, the exact details of what is going on here is problematic to me. As usual, the newspapers tend to garble and confuse many issues. Consider this sentence: "All five are brain-damaged because of a mutation in a gene 17p, located on chromosome 17, which occurred because mother and father are closely related: Hatice's maternal grandmother was the sister of Resit's father (which makes them one-sixteenth related)." This is likely poor grammar, but the mutation did not occur because of a close genetic relationship. That is, a high degree of inbreeding does not spontaneously increase the rate of mutation, rather, consanguineous marriages tend to increase the chances that deleterious mutations will be unmasked.
The principle is simple. Consider an assertion sometimes made that every human being has 3 lethal recessives. The point here is that if the allele, the genetic variant, were carried as two copies (humans are diploid, we have two copies of all genes) so that the individual was homozygous, than negative phenotypic consequences would ensue and reduce fitness. So, cystic fibrosis is a lethal recessive, if a long acting one (with medication today CF patients can survive deep into their 30s). 1 out of 20 Western Europeans carry the CF mutation. Of these individuals, almost all of them are heterozygous, that is, they carry one "good copy" and a "bad copy." These individuals do not manifest any negative phenotypic outcomes because the good copy of the gene is sufficient for normal functioning. The problem occurs when two individuals who carry a copy of the gene mate, there is a 25% chance that the child will receive both bad copies and so the negative phenotypic consequences will be unmasked. If 1 out of 20 individuals in the population is heterozygous, you have a random mating chance of 1/400 of carriers pairing up, and a 1/4 chance that any resultant offspring will exhibit CF.
So, consider a situation where you have one parent who is a CF carrier. This individual's children with a homozygous "wild type" individual (no bad copies) will have a 1/2 chance of being a barrier. Now, imagine that the children mate with each other. Each of the children has a 1/2 chance of being a CF carrier, so you have a 1/4 chance two carriers will mate, and a 1/4 chance that offspring with negative phenotypic consequences will result. Multiplying out the independent probabilities implies that if a carrier's children mate incestuously the expectation of a grandchild exhibiting CF is 1/8. Compare this to someone whose children do not mate incestuously, each of the children have a 1/2 chance of being carriers, and each of these have a 1/20 chance of mating another carrier, so you have a 1/40 chance of having a double carrier pairing. 1/4 of the children will exhibit the phenotype, so you have a 1/160 chance of a grandchild of this individual having CF. In other words, the probability difference between sibling matings and non-incestuous matings of resulting in a CF grandchild for a heterozygous individual is a factor of 20. This is an extreme situation, but multiple generations of mild incest can be problematic, in other words, I am skeptical that the coefficient of relatedness is simply 1/16.
Again, unfortunately, the atavism angle is emphasized. This is good copy, but we should be skeptical of this. It is possible, but that does not imply it is probable. It seems that the 17p mutation is a loss of function which has had wide pleiotropic effects. I am skeptical that the ancestral gene shifted from null function to a new function. As Carl Zimmer pointed out bipedalism is a complex and exceptional trait which resulted in the retrofitting of a host of other aspects of our morphology and physiology. Though it might not have emerged in a classic gradualistic fashion, it seems unlikely to have been the result of a single positive mutation around which modifier genes evolved over hundreds of generations. So, if the gene that is causing this non-bipedalism is of a different nature on the sequence level from the character of our ancient pre-hominin ancestors, what exactly can be infer about the evolution of bipedalism from this single family? I don't know.
Finally, there is the issue that one of the children in this family who carries the 17p mutation does not seem to exhibit the aberrant traits of his siblings. The lead scientist who is quoted in the article suggests that this is both nature and nurture, that a particular environmental context increased the probability of this phenotype expressing itself given the initial genotype. In the technical literature this would probably be termed incomplete penetrance. But, I want to zoom in on the conclusion and question how deeply Humphrey has thought this through, or, how much we should trust The Times if it has taken him out of context:
Professor Humphrey says that a combination of factors - the genetic defect, the huge family, limited parental attention, sibling imitation, skeletal anomalies, the lack of intervention from the outside world - led to this remarkable outcome.
"If there was just a one in a thousand chance of each of these things happening, this soon adds up to a one in a billion chance of it happening in the same family. It's not surprising we've never seen it before. We may never see it again."
In the first paragraph there are a host of variables listed, and in the second Humphrey seems to be implying that these variables are independent, that each offspring is an independent trial which can be viewed separately. I don't see how this works, it seems that many of the variables listed above should exhibit some correlational and interactional effects with each other. I have shown above how the probability of a the genetic defect manifesting itself increases greatly within the same family. This family should also likely foster a similar environmental input to its offspring, even if it varies. I am probably confused, because I don't see exactly what Humphrey is trying to get at in the second paragraph in regards to probabilities. Finally, the nature and nurture in conjunction might be correct, but, there is an alternative explanation for incomplete penetrance, and that is that traits are often polygenic in a way we do not comprehend because of an epistatic, gene-to-gene interaction, parameter within the equation. In other words, the "normal" son might carry a gene on another locus which masks the non-bipedal phenotype.
In short, I'm convinced this isn't a hoax, and it might be medically interesting. But I am also skeptical of the claim that this tells us something on a broad evolutionary genetic and palaeoanthropological scale.
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The mutation on 17p has been identified by a Turkish/German team in Berlin headed by Professor Stefan Mundlos. They suggest, some would say controversially, that this mutation could have knocked out a gene that plays a role in bipedal walking, atavastically exposing an earlier form of walking.
Professor Humphrey believes, however, that this mutation has merely caused the cerebellar hypoplasia confirmed by MRI scans, and which makes it so difficult for them to balance upright. He argues that it's likely to be a conjunction of other factors that has kept the siblings on all fours. These include what seems to be a familial predisposition to bear-crawling as children (all 19 children, including all the healthy ones, did it), and a mix of other cultural influences such as lack of a pro-active health service.
But whatever the mix of nature and nurture, the family still raises some interesting evolutionary questions. They mostly use a diagonal gait better suited to branch-walking than terrestial walking (suggesting it could still be hard-wired in us). They are also palmigrade rather than knuckle-walkers, and the paleoanthropologists have expressed interest in seeing what impact walking this way has had on their skeletons. It could help them tease out what anatomical features are and are not important in the fossil record.
It is also interesting that they balance extremely well on four, showing none of the ataxia they display on two. This has led another researcher, Dr John Skoyles (LSE), to suggest that the gene that has been knocked out might be one which has a role in humans' "superbalance" ability.
As you might imagine, we have been dismayed by some of the newspaper reporting. Not one major newspaper has reported the science accurately - a result, of course, of a widespread lack of understanding of even basic scientific principles. There has also been considerably confusion over which scientist is saying what (is is only, for instance, the Turkish scientist, Professor Uner Tan, who suggests they are a wholesale genetic throwback).
Our film will, I hope, redress the balance and be seen as a sensitive, thorough and thought-provoking record of the family/phenomenon. We made it not for voyeuristic reasons (although of course the quadrupedal siblings are visually arresting) but because we thought it raised all kinds of fascinating scientific, and many other, questions. I think the reason it's created such a fuss because bipedality is something that defines us as human beings - separate and distinct from beasts - and their existence is challenging philosophically. You only have to look at the Bible, for instance, to see how the word "upright" is loaded with meaning about purity, morality etc. That's ingrained very deeply in us.
Jemima Harrison
Passionate Productions
As far as I can see, the "atavism" conjecture is a lot simpler than you've painted it.
For whatever reason, this particular mutation abolishes the ability to walk upright. However, all bearers of the mutation have hit on the *same* replacement gait. We don't see some crawling, some shuffling on their bottoms, some knuckle-walking and some wrist-walking.
This suggests a possibility that the necessary neural circuitry for a reasonably efficient wrist-walking gait is still part of modern human physiology, simply hidden due to the fact that by and large we walk upright. That in turn suggests that wrist-walking may have been an habitual gait at some stage of our evolution. It's an intriguing suggestion, as the alternative quadrupedal gait (knuckle walking) is extremely destructive to the fingers are would have limited our ancestors' dexterity.
However, in the absence of fossil skeletal evidence, I don't see any way of lifting this above the realms of conjecture.
However, all bearers of the mutation have hit on the *same* replacement gait.
But they have not hit upon it independently -- they are all members of the same family. It's possible that the first family member found that method of 'walking' convenient, and his/her relatives mimicked it.
I am not a scientist, just an ordinary person.
I think the reason this family are walking this way is purely a balance thing, because of the nature of their brain abnormalities, similar to being drunk for us (how many of us have had a hangover and been so off balance, you crawl to the loo?). The reason they do not use their knees is probably that it would hurt,nothing more.
I used to work with a boy who had autism and other outward signs of brain damage. He walked very similar to a toddler taking their first steps and would sometimes get down on the floor as if he was tired of trying to balance.
It struck me how loving, innocent and pure the family were and I felt time would be better spent by the visitors educating the village about the family and encouraging them to accept and respect them.
They appeared quite happy with their lives and the way they walked and I think it is arrogant of us to think they need mending. What is so great about the modern world anyway? Does it bring the happiness they showed?
They showed the young man in a temper and said it was his frustration at not walking. How did they know this? Everyone gets in a strop at times don't they?
Questioning the mothers abilities seemed ridiculous too. Children mostly get up and walk themselves, and there have been large families through history who may have been thought to have had little parental input, but have walked.
They used to say that the mothers of children with autism were cold. I thought this attitude was from the dark ages.
The family had a special beauty and should be left to live as they are apart from the need to educate the village about them and giving them respect and support. That to me was their biggest burden.
Janet,
Do you really think the children enjoyed walking on all fours their entire lives? Did you miss the part about their whole neighborhood hating them and making fun of them? Did you not catch the statement by the father that he would give absolutely anything for them to be able to walk?
And yet no one ever bothered to give them so much as a CANE, much less a $30 walker...
I mean at any moment their father could have snapped a couple branches off a tree and make some walking sticks.
I think you can easily put all the blame on the loving but tragically uncreative parents and their ignorant culture for the condition of their children. Sure they seemed pretty happy, but I doubt their happiness had anything to do with walking on all fours. No doubt they would have been happier still with some physical therapy...or at least a cane.
Well, I am with Janet. I think this sounds like such a crock. There are obviously physiological factors at work for some of these people, and social/environmental factors for the others. A throwback to earlier times my foot!
The fact they have all ended up using the same gait would reflect the fact that for a human being to walk on all fours, that gait is the most effective. It's not rocket science to figure that out. The same applies to comment about how these people use their palms and not their knuckles. Sheesh!! Again, just think about it for a second or two. Of course they do. So would you. A human being can't walk on his knuckles or fingers for the simple reason it hurts too much. We aren't designed to do it. Just have a go yourself.
All that has happened is that a group of people have taken to walking in that fashion. The strategy is one they've adopted to overcome physiological limitations, and it's how people the world over adapt. We don't see suggestions that a person without arms who uses their feet to manipulate objects is somehow using a racial memory to do so, now do we?
I come from a position of some experience in this too. As a child I did a LOT of quadrupedal walking, running and jumping. I took to it early on because it was fun, and because I had a tendency to want to imitate animals. My gait was very much the same as these people's, and involved palm walking. I was also able to run very quickly in a kind of diagonal lope similar to a monkey. And I can still do it at 47 years of age. No big deal, and unless my heavy brow ridge, stunted legs and silvery back hair are factored in, hopefully not a suggestion that I am an evolutionary throwback for being able to do so...
What a load of twaddle. At least there is a good side to it all, the family have received help and will hopefully enjoy a much improved quality of life from here on.
I can't believe that this is even true. It's one of those things you have to see to believe. If so- I have to say that "walking on all fours" is just one of the many problems these children face (and to think I was upset for my son tonite when he struck out at his ball game...) all I can say is if it is due to incest, I hope it stops. This family will be in my prayers.