This is Improbable Too Page 13
The scientists conducted an experiment with armadillos in an enclosed underground dirt heap at the São Paulo zoo. They stacked coloured, flaked stones and bits of ceramic into layers, then let the animals have their way.
The armadillos proved to be impressive object-movers. Araujo and Marcelino proudly report: ‘Some of our findings have never been reported in the literature, such as the fact that armadillos can translocate artifacts downward to great depths as well as expel them towards the surface.’
To a naïve non-archaeologist, such concerns may seem like child’s play. But for good archaeologists, child’s play is sometimes a serious problem.
Norman Hammond and the then infant Gawain Hammond illustrated this by doing an experiment. The older Hammond is a professor, now based at Boston University. The Hammonds’ report, ‘Child’s Play: A Distorting Factor in Archaeological Distribution’, appeared in 1981.
The elder Hammond created an artificial trash pile one metre in diameter. He stocked it with wine jars, liquor bottles and twelve mostly-empty beer cans. The younger Hammond was then permitted to play briefly in the pile. The report concludes: ‘The interpolation of “child-play” may profoundly modify the initial archaeological pattern, and transmit it into an arbitrary pattern with an unrelated structure. The causes of this change must be allowed for in investigations of artifact.’
For measuring how the course of history, or at least the contents of an archaeological dig site, can be scrambled by the actions of a live armadillo, Araujo and Marcelino were awarded the 2008 Ig Nobel Prize in archaeology.
Araujo, Astolfo Gomes de Mello, and José Carlos Marcelino (2003). ‘The Role of Armadillos in the Movement of Archaeological Materials: An Experimental Approach’. Geoarchaeology 18 (4): 433–60.
Hammond, Gawain, and Norman Hammond (1981). ‘Child’s Play: A Distorting Factor in Archaeological Distribution’. American Antiquity 46 (3): 634–6.
In brief
‘The Problem of the Locomotive-God’
by W.S. Taylor and E. Culler (published in the Journal of Abnormal and Social Psychology, 1929)
Success at your finger tips
A 2011 Italian study points towards a handy way to identify who might become a top doctor. The method is simple: compare the lengths of a person’s second finger and fourth finger. The technique is disclosed in the monograph ‘The Second-To-Fourth Digit Ratio Correlates with the Rate of Academic Performance in Medical School Students’ and appears in the May-June issue of the journal Molecular Medicine Reports.
Researchers who spend time studying this finger ratio – the individuals who have found meaning by looking to both sides when someone shows them a middle finger – call it ‘2D:4D’. That’s shorthand for the phrase ‘second-to-fourth digit length ratio’. The big dog, the Einstein of the field, is Professor John Manning of the University of Liverpool, whose work has included how to spot footballing stars of the future by looking at finger length (for more on Manning and other high achievers in the field, see page 131).
The authors of the Italian study, mostly medical researchers from the University of Catania in Sicily, and Kore University in Enna, write: ‘2D:4D has been shown to predict the success of men who play sports and of financial traders.’ But, they claim, their paper is the first to reveal what 2D:4D says about high flyers in a highly competitive university system such as the state-run Italian medical schools.
After measuring the fingers of forty-eight male medical students using callipers accurate to 0.2 millimetres, they concluded that students with a slightly lower 2D:4D ratio of the right hand (although, confusingly, it is not quite clear whether this means the fingers are more similar or different in length) are more likely to be successful. The researchers noted in particular how those who passed their medical school admissions test had a significantly lower 2D:4D ratio of the right than those who failed. Interestingly, however, finger ratios could not predict how those students performed in their exams.
It’s possible that identifying future stars by examining their fingers is even better than choosing people at random (see page 293). But until and unless somebody does the research, no one can say for sure.
Coco, Marinella, Valentina Perciavalle, Tiziana Maci, Ferdinando Nicoletti, Donatella Di Corrado and Vincenzo Perciavalle (2011). ‘The Second-to-Fourth Ratio Correlates with the Rate of Academic Performance in Medical School Students’. Molecular Medicine Reports 4: 471–6.
Manning, John T., and Rogan P. Taylor (2001). ‘Second to Fourth Digit Ratio and Male Ability in Sport: Implications for Sexual Selection in Humans’. Evolution Human Behavior 22 (1): 61–69.
In brief
‘Pointing the Way: The Distribution and Evolution of Some Characters of the Finger Muscles of Frogs’
by Thomas C. Burton (published in American Museum Novitates, 1998)
The meaning of the finger
Most people who have done research on fingers have either measured them or tried to repair them.
Among them was V. Rae Phelps of the University of Texas and Tulane University in New Orleans. In 1952, Phelps compiled a capsule history of early finger findings, waxing nearly poetic about researchers’ many missteps and mistakes. In his influenced monograph ‘Relative Index Finger Length as a Sex-influenced Trait in Man’, published in the American Journal of Genetics, he reports: ‘Ecker (1875) noted that three manifestations of relative finger length may be discerned in the living model: index finger shorter than ring finger; index finger equal in length to ring finger; and index finger longer than ring finger. Many of the earlier workers failed to recognize this variability’.
He went on to name names. ‘Gerdy (1829) stated that the index finger is always shorter than the ring finger, while according to Carus (1853) and Humphry (1861), the index finger exceeds the ring finger in length’, he notes. ‘Langer (1865) declared that the index finger is shorter than or nearly equal to the ring finger. Alix (1867), Grining (1886), Baker (1888), Schultz (1926), and Wood-Jones (1920, 1941) point out that although the index finger is usually shorter than the ring finger, it may in certain circumstances exceed the length of the ring finger’.
Phelps concentrated mostly on the lengths of fingers and the failures of his predecessors, choosing not to speculate on what, if anything, fingers themselves might mean.
Thankfully, we are experiencing a golden age in finger investigations. Some pioneers began to wonder, ‘What do fingers mean?’ Modern finger researchers see profound implications in the relative-finger-length possibilities that Ecker (and Phelps) pointed out, most especially, 2D:4D ratios. Here is the big idea, in a nutshell:
The body’s many hormones are involved in many things during foetus-hood, childhood and adolescence. These many things happen at various times and in various ways.
Each hormone involved in these things has many different effects. Scientists have noticed some of these effects, and understand a few of them, at least a little bit.
Testosterone is one of the hormones that scientists have noticed.
Testosterone may somehow, at some time, affect how long fingers grow.
The relative lengths of a person’s fingers may say something about how much testosterone was in the body at some point earlier in their life.
The amount of testosterone in a person’s body at some point earlier in their life affects lots of other things.
This big idea is often credited to Professor John T. Manning. Thus his status as the large canine, the genius of the field. But fingers are hot in the research world, and Manning is not alone in eyeing them.
Emma Nelson, a researcher and visiting lecturer at the University of Chester who sometimes works with Professor Manning, has her own series of finger-related studies. One examines the 2D:4D ratio of hand outlines stencilled on cave walls. Nelson hopes that 2D:4D will show whether the hands belonged to ancient cave men or to cave women. Another study uses finger-length ratio to better understand the topic ‘testes size and dominance in a Group of Captive Chimpanzees�
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Martin Voracek of the University of Vienna (featured on page 299) takes a manifold interest in fingers. Sometimes, he collaborates with Professor Manning, but he also does research independently.
Drs Voracek and Manning recently reported that, by measuring a man’s 2D:4D, they could predict, to some degree, how many sexual partners the man would have. But, they say, this works for heterosexual men, not for homosexuals. So far, they express confidence only that it applies to Austrian men.
Voracek and Manning also published a report on the perhaps inevitable question of whether the finger length ratio is related to the length of the penis. Yes, they say, it is.
Teaming with other colleagues, Voracek also published a study about how 2D:4D relates to the performance of skilled fencers. (Manning turned his own attention to 2D:4D and surfers.)
S. Marc Breedlove, a professor of neuroscience at Michigan State University, has become a giant of finger research. In 2000, his study called ‘Finger-Length Ratios and Sexual Orientation’ appeared in the journal Nature. It features a handy graph. The reader can see that, on average, gay and straight women have distinctly different finger ratios – and that gay and straight men each have their own distinctly differing ratios. These distinctions, curiously, are true of the right hand or of the left, but not of both.
Breedlove made a more specific discovery two years later. He and several colleagues published a study called ‘Differences in Finger Length Ratios Between Self-identified “Butch” and “Femme” Lesbians’. Their findings are summed up in this sentence: ‘We surveyed individuals from a gay pride street fair and found that lesbians who identified themselves as “butch” had a significantly smaller 2D:4D than did those who identified themselves as “femme”.’
One proposed meaning of the finger
There are also finger financialists. Professor Siegfried Dewitte is an applied economist at Katholieke Universiteit Leuven. Bram van den Bergh trained under Dewitte. Their work, compared to some of their competitors, is less abstruse. For instance, in ‘Second to Fourth Digit Ratio and Cooperative Behavior’, published in Biological Psychology in 2006, they ‘predicted that a low 2D:4D would be associated with high levels of egoism and altruism and low levels of common cooperativeness (i.e. contributing exactly one’s fair share).’ However, they ‘found the exact opposite’.
There are hundreds of other finger celebrities. Dr Mark Brosnan, a psychology researcher at the University of Bath, may be the most notorious. Brosnan studied the fingers of one hundred of his colleagues at the university. He reports that the digit ratio is significantly different for science teachers than for those who teach humanities or social science. No one has tried to dispute this finding.
Phelps, V. Rae (1952). ‘Relative Index Finger Length as a Sex-influenced Trait in Man’. American Journal of Human Genetics 4 (2): 72–89.
Bennett, M., John T. Manning, Christian J. Cook and Liam P. Kilduff (2010). ‘Digit Ratio (2D:4D) and Performance in Elite Rugby Players’. Journal of Sports Sciences 28 (13): 1415–21.
Manning, John T. (2008). The Finger Book. London: Faber and Faber.
Nelson, Emma, John T. Manning and Anthony G.M. Sinclair (2006). ‘Using the 2nd and 4th Digit Ratio (2D:4D) to Sex Cave Art Hand Stencils: Factors to Consider’. Before Farming 1: n.p.
Nelson, Emma, Christy L. Hoffman, Melissa S. Gerald and Susanne Shultz (2010). ‘Finger Length Ratios (2D:4D) and Dominance Rank in Female Rhesus Macaques (Macaca mulatta)’. Behavioral Ecology and Sociobiology 64: 1001–9.
Nelson, Emma, Campbell Rolian, Lisa Cashmore and Susanne Shultz (2011). ‘Digit Ratios Predict Polygyny in Early Apes, Ardipithecus, Neanderthals and early Modern Humans But Not in Australopithecus’. Proceedings of the Royal Society B 278: 1556–63.
Voracek, Martin, John T. Manning and Ivo Ponocny (2005). ‘Digit Ratio (2D:4D) in Homosexual and Heterosexual Men from Austria’. Archives of Sexual Behavior 34 (3): 335–40.
Voracek, Martin, and John T. Manning (2003). ‘Length of Fingers and Penis Are Related through Fetal Hox Gene Experession’. Urology 62 (1): 201.
Voracek, Martin, Barbara Reimer, Clara Ertl and Stefan G. Dressler (2006). ‘Digit Ratio (2D:4D), Lateral Preferences, and Performance in Fencing’. Perception and Motor Skills 103 (2): 427–46.
Voracek, Martin, Barbara Reimer and Stefan G. Dressler (2010). ‘Digit Ratio (2D:4D) Predicts Sporting Success among Female Fencers Independent from Physical, Experience, and Personality Factors’. Scandinavian Journal of Medicine & Science in Sports 20 (6): 853–60.
Kilduff, Liam P., Christian J. Cook and John T. Manning (2011). ‘Digit Ratio (2D:4D) and Performance in Male Surfers’. Journal of Strength and Conditioning Research 25 (11): 3175–80.
Williams, Terrance J., Michelle E. Pepitone, Scott E. Christensen, Bradley M. Cooke, Andrew D. Huberman, Nicholas J. Breedlove, Tessa J. Breedlove, Cynthia L. Jordan and S. Marc Breedlove (2000). ‘Finger-length Ratios and Sexual Orientation’. Nature 404 (30 March): 455–6.
Brown, Windy M., Christopher J. Finn, Bradley M. Cooke, and S. Marc Breedlove (2002). ‘Differences in Finger Length Ratios Between Self-identified “Butch” and “Femme” Lesbians’. Archives of Sexual Behavior 31 (1): 123–7.
Brosnan, Mark J. (2006). ‘Digit Radio and Faculty Membership: Implications for the Relationship between Prenatal Testosterone and Academia’. British Journal of Psychology 97: 455–66.
— (2008). ‘Digit Ratio as an Indicator of Numeracy Relative to Literacy in 7-year-old British Schoolchildren’. British Journal of Psychology 99: 75–85.
—, V. Galllop, N. Iftikhar and E. Keogh (2011). ‘Digit Ratio (2D:4D), Academic Performance in Computer Science and Computer-related Anxiety’. Personality and Individual Differences 51 (4): 371–5.
Voracek, Martin, John T. Manning and Stefan G. Dressler (2007). ‘Repeatability and Interobserver Error of Digit Ratio (2D:4D) Measurements Made by Experts’. American Journal of Human Biology 19 (1): 142–6.
Millet, Kobe and Siegfried Dewitte (2006). ‘Second to Fourth Digit Ratio and Cooperative Behavior’. Biological Psychology 71 (1): 111–15.
What am I missing?
Fuelled with curiosity, some scientists exploit – lovingly, proudly – the investigative trick featured in Arthur Conan Doyle’s 1892 story ‘Silver Blaze’. There, a baffled police inspector seeks help from the great autodicact/detective Sherlock Holmes:
[INSPECTOR GREGORY:] ‘Is there any point to which you would wish to draw my attention?’
[HOLMES:] ‘To the curious incident of the dog in the night-time.’
[INSPECTOR GREGORY:] ‘The dog did nothing in the night-time.’
‘That was the curious incident’, remarked Sherlock Holmes.
Science journals feature many papers in which scientists rely on this technique, riding it to, or at least in the direction of, glory. You can see that happening in a report called ‘The Mystery of the Missing Toes: Extreme Levels of Natural Mutilation in Island Lizard Populations’, published in 2009 in the journal Functional Ecology.
The co-authors – Bart Vervust, Stefan Van Dongen and Raoul Van Damme at the University of Antwerp, Belgium, and Irena Grbac at the Natural History Museum of Croatia – ‘report on an exceptionally large difference in toe-loss incidence between two populations of Podarcis sicula lizards living on small, neighbouring islands in the Adriatic Sea. We caught 900 lizards and recorded the number and location of missing toes.’ Having gathered that data, the scientists then walked through the logic of ‘five non-mutually exclusive hypotheses concerning differences in bite-force capacity, bone strength …’ and so forth.
Unlike the fictional British detective, this very real Belgian/Croatian research team failed to discover a tidy, satisfying solution to their mystery. Nonetheless, they found reason for cheer, explaining that ‘such tests can reveal how likely each of these explanations is, even if the processes leading to the phenomenon are difficult to observe directly.’
Figure: ‘Device for measuring bite
force needed for breaking a toe’ from ‘The Mystery of the Missing Toes’
The method sometimes flops. That’s evident in a different study about lizards, published by the Chilean/US team of Fabian Jaksic and Stephen Busack in 1984 in the journal Amphibia-Reptilia. Jaksic and Busack sum things up in their title: ‘Apparent Inadequacy of Tail-loss Figures as Estimates of Predation upon Lizards’.
Some scientists spurn or ignore the method, or find that it does not apply to their particular investigation, however. In 1994, G.J. Adams and K.G. Johnson at Murdoch University in Australia published a study with what appears to be a blatantly, proudly Sherlock Holmesian title. Adams and Johnson called their report ‘Behavioural Responses to Barking and Other Auditory Stimuli during Night-time Sleeping and Waking in the Domestic Dog (Canis familiaris)’. Curiously, Adams and Johnson neither use nor allude to the Sherlock Holmes trick.
They explain that they filmed twelve dogs ‘at night in their usual urban habitats, whilst alert, in quiet sleep and in active sleep’. They subjected each dog to six different audio recordings: ‘a single bark; repeated barking; breaking glass; a motorcycle; a bus; and ‘rowdy young people discussing burglurizing [sic]’. They discovered, they say, that ‘dogs were found to be significantly more responsive to auditory stimuli when alert than when asleep.’
Vervust, Bart, Stefan Van Dongen, Irena Grbac, and Raoul Van Damme (2009). ‘The Mystery of the Missing Toes: Extreme Levels of Natural Mutilation in Island Lizard Populations’. Functional Ecology 23 (5): 996–1003.