Contagious Yawning from Human to Domestic Dogs: Is It Possible? What Are The Implications?

Yawning is a phenomenon that occurs not only in human but also in other animals such as mammals, fishes, amphibians, reptiles and birds (Heusner, 1946; Baenninger, 1987; Gallup et al., 2009). There are many proposed reasons and functions as to what elicit yawning behavior in an individual but little is known about the role of contagious yawning and how animals can catch yawns from other species. Even though yawning is widespread in the animal kingdom, contagious yawning has only been reported in humans, chimpanzees (Pan troglodytes), stumptail macaques (Macaca arctoides) and recently in domestic dogs (Canis familiaris) (Provine, 1986; Platek et al., 2003; Anderson et al., 2004; Paukner & Anderson 2006; Joly-Mascheroni et al., 2008; Harr et al., 2008). In addition, studies have shown that there is a positive correlation in the susceptibility of contagious yawning with empathy and theory of mind (Platek et al., 2003; Preston & de Waal, 2002), and that emotional closeness and relatedness between an individual is key to eliciting contagious yawning in human (Norscia & Palagi, 2011).

Contagious yawning has been reported in humans, chimpanzees, stumptail macaques and  domestic dogs.

There have been many suggestions on the roles of contagious yawning, especially in primates. Some literatures hypothesized that contagious yawning in primates plays potential roles in communication, social interaction, empathy and self-awareness (Deputte, 1994; Daquin et al., 2001; Platek et al., 2003; Gallese et al., 2004; Platek et al. 2005) while others thinks that it is a stereotyped action behavior and an innate releasing mechanism (Provine, 1986). In addition, Platek et al. (2003) showed a positive correlation in the susceptibility to contagious yawning with self-face recognition and theory of mind stories while children with autism spectrum disorder showed an absence in contagious yawning (Senju et al., 2007) suggests that contagious yawning may be related to empathy (Preston & de Waal, 2002). A recent study on yawn contagion in human shows that related individuals (r ≥ 0.25) were the ones that are more susceptible to contagious yawning, and concludes that emotional closeness between an individual is key to contagious yawning in human as opposed to other variable such as sex or country of origin (Norscia & Palagi, 2011).

Although yawning is widespread in the animal kingdom, contagious yawning has only been reported in humans (Provine, 1986; Platek et al., 2003), chimpanzees (Anderson et al., 2004), stumptail macaques (Paukner & Anderson 2006) and domestic dogs (Joly-Mascheroni et al., 2008; Harr et al., 2008). Contagious yawning from human to domestic dogs  is interesting because it could further elucidate if empathy was inadvertently selected for in domestic dogs as they evolve side by side with modern humans. If yawns can indeed be passed from human to domestic dogs, we can posit that domestic dogs are capable of empathy. Further experiment on contagious yawning from the owner (human) to domestic dogs could also elucidate whether yawns are more susceptible based on emotional closeness as per Norscia & Palagi's (2011) research, albeit their subjects are all humans.

Neonatal macaque imitation the expression of a researcher.

Gallese et al. (2004) contended to the fact that mirror neurons play an integral part on the theory of mind and empathy. Later experiment by Iacoboni et al. (2005) posits that mirror neurons are involved in understanding the intention of others. By using an FMRI, human subjects were exposed to 3 types of stimuli on 24 second video clips. These stimuli show grasping hand action without a context (Action), context-only (Context), and grasping hand with and without context (Intention). In the Action stimuli, a hand was shown grasping a cup in the absence of context and an objectless background. Two types of grasping actions were used: either precision grasping (hand grasping the cup handle) or whole-hand grasping (hand grasping the cup body). The Context stimuli showed three dimensional objects such as a teapot, a mug or a cookie just before or just after having tea to elicit a drinking or cleaning context. For the Intention stimuli, the subjects were presented with both grasping actions in both drinking and cleaning context. When presented with the Intention stimuli, there is a significant signal increase in the premotor cortex; the posterior part of the inferior frontal gyrus and the adjacent sector of the ventral premotor cortex where hand actions are represented. The authors argue that the premotor mirror neuron areas are involved in understanding the intention of others, evident from a spike of signal in the FMRI when humans were exposed to Intention stimuli in the experiment.

Other experiments have shown that in pigtailed macaques, Macaca nemestrina, mirror neurons are also found in the inferior frontal gyrus (the F5 region). This region responded when the macaques make an active movements and also when they observe an experimenter making meaningful movements. (di Pellegrino et al., 1992; Gallese et al., 1996; Rizzolatti & Craighero, 2004; Hickok, 2009).

In a study by Platek et al. (2005), the authors found that the posterior cingulate and precuneus were activated during contagious yawning. These two regions are associated with the theory of mind and empathy. In another study from the same year, Schürmann et al. (2005) found that the superior temporal sulcus was the area that gets activated during contagious yawning. The superior temporal sulcus region is involved in the perception of eye gaze of others and are crucial in determining where others’ emotion are being directed through eye gaze (Campbell et al., 1990). Thus, neuroimaging results from Platek et al. (2005) and Schürmann et al. (2005) contradict each other in isolating the region of the brain that is activated during contagious yawning.

Two studies on contagious yawning from human to domestic dogs were published by Joly-Mascheroni et al. (2008) and Harr et al. (2008) in the same year. Joly-Mascheroni et al. (2008) were the first to demonstrate that human yawns are contagious to domestic dogs and that human yawns would elicit a yawning response from a non-primate species (domestic dog). In this ingenious experiment, Joly-Mascheroni et al. (2008) had 29 domestic dogs observed human yawning and making control mouth movements (not yawns). Out of the 29 domestic dogs, 21 of them yawned after observing a human yawning but none when exposed to control mouth movements (the control in the study). The experiment yielded impressive result, where 72% of the domestic dogs yawned when exposed to a human yawning. This is a higher rate than contagious yawning between humans (45% – 60%) (Provine, 1986; Platek et al., 2003) and from human to chimpanzee (33%) (Anderson et al., 2004). Joly-Mascheroni et al. (2008) posit from this experiment that domestic dogs possess a rudimentary empathic capability and that it helps in moderating human-dog interaction and communication.

A later study by Harr et al. (2008) in the same year also investigated whether human yawns are contagious to domestic dogs but used a different method than that of Joly-Mascheroni et al. (2008). Harr et al. (2008) used 15 domestic dogs in their experiment; the domestic dogs were shown video clips of humans and domestic dogs displaying yawns and open mouth expressions (not yawns) to determine whether these two social stimuli would elicit yawning in these domestic dogs. Their results show that the domestic dogs yawned on both stimuli (yawn and open mouth expressions) with no significant difference as determined by paired t test. Citing methodological difference than that of Joly-Mascheroni et al. (2008), Harr et al. (2008) posit that their results were due to using video clips instead of using live human models. They also conclude that it is possible that domestic dogs, like humans, attended differently to video stimuli than that of a live model.

Järveläinen et al. (2001) showed that in humans, there is a stronger reactivity time in the mirror neuron system when viewing live motor act than that of an artificially presented act. It is possible that domestic dogs also pay less attention to an artificially presented act than that of a live motor act. Understanding the umwelt of domestic dogs is important when using them as experimental subjects and to answer species-specific questions. Domestic dogs are excellent at reading human communicative and visual cues (Joly-Mascheroni et al., 2008) but maybe only so on live model and not video clips as evident from Harr et al. (2008) experiment. Thus, experiment on contagious yawning from human to domestic dogs should considering using only live models and not video clips.

P/S - Sorry if I made you yawn ;)

References

Anderson, J. R., Myowa-Yamakoshi, M., & Matsuzawa, T. (2004). Contagious yawning in chimpanzees. Proc. R. Soc. B, 271(Suppl. 6), S468–S470.

Baenninger, R. (1987). Some comparative aspects of yawning in Betta splendens, Homo sapiens, Panthera leo, and Papio sphinx. J. Comp. Psychol. 101, 349–354.

Campbell, R., Heywood, C.A., Cowey, A., Regard, M., & Landis, T. (1990). Sensitivity to eye gaze in prosopagnosic patients and monkeys with superior temporal sulcus ablation. Neuropsychologia, 28(11), 1123-1142.

Daquin, G., Micallef, J. & Blin, O. (2001). Yawning. Sleep Med. Rev. 5, 299–312.

Deputte, B. L. (1994) Ethological study of yawning in primates. 1. Quantitative analysis and study of causation in 2 species of Old World monkeys (Cercocebus albigena and Macaca fascicularis). Ethology, 98, 221–245.

di Pellegrino, G., Fadiga, L., Fogassi, L., Gallese, V., & Rizzolatti, G. (1992). Understanding motor events: A neurophysiological study. Experimental Brain Research, 91, 176–180.

Gallese, V., Fadiga, L., Fogassi, L., & Rizzolatti, G. (1996). Action recognition in the premotor cortex. Brain, 119, 593–609.

Gallese, V., Keysers, C., & Rizzolati, G. (2004). A unifying view of the basis of social cognition. Cognitive Sciences, 8(9), 396-403.

Gallup, A. C., Miller, M. L. & Clark, A. B. (2009). Yawning and thermoregulation in budgerigars, Melopsittacus undulates. Animal Behaviour, 77, 109e113.

Harr, A.L., Gilbert, V.R. & Phillips, K.A. (2008). Do dogs (Canis familiaris) show contagious yawning? Animal Cognition, 12, 833-837.

Hickok, G. (2008). Eight Problems for the Mirror Neuron Theory of Action Understanding in Monkeys and Humans. Journal of Cognitive Neuroscience, 27(7), 1229-1243.

Iacoboni, M., Molnar-Szakacs, I., Gallese, V., Buccino, G., Mazziotta, J.C., & Rizzolatti, G. (2005). Grasping the Intentions of Others with One's Own Mirror Neuron System. PLoS Biology, 3(3), e79. doi:10.1371/journal.pbio.0030079.

Järveläinen, J., Schürmann, M., Avikainen, S., & Hari, R. (2001). Stronger reactivity of the human primary motor cortex during observation of live rather than video motor acts. Neuroreport, 12, 3493-3495.

Joly-Mascheroni R.M., Senju, A., & Shepherd, A.J. et al. (2008). Dogs Catch Human Yawns. Biology Letters, 4, 446-448.

Norscia, I. & Palagi, E. (2011). Yawn Contagion and Empathy in Homo sapiens. PLOS One, 6(12): e28472. doi:10.1371/journal.pone.0028472.

Paukner, A. & Anderson, J. R. (2006). Video-induced yawning in stumptail macaques (Macaca arctoides). Biology Letters 2, 36–38.

Platek, M.S., Critton, S.R., Myers, T.E. & Gallup, G.G. (2003). Contagious yawning: the role of self-awareness and mental state Attribution. Cognitive Brain Research 17, 223–227.

Platek, S.M., Mohamed, F.B., & Gallup, G.G. (2005). Contagious yawning and the brain. Brain Res Cogn Brain Res, 23, 448–452.

Preston, S. D. & de Waal, F. B. (2002). Empathy: Its ultimate and proximate bases. Behav. Brain Sci. 25, 1–20.

Provine, R.R. (1986). Yawning as a Stereotyped Action Pattern and Releasing Stimulus. Ethology, 72(2), 109-122.

Rizzolatti, G., & Craighero, L. (2004). The Mirror-Neuron System. Annu. Rev. Neurosci, 27, 169 92.

Schürmann, M., Hesse, M.D., Stephan, K.E., Saarela, M., Zilles, K., Hari, R., & Fink, G.R. (2005). Yearning to yawn: the neural basis of contagious yawning. Neuroimage, 24, 1260 1264.

Senju, A., Maeda, M., Kikuchi, Y., Hasegawa, T., Tojo, Y. & Osanai, H. (2007). Absence of contagious yawning in children with autism spectrum disorder. Biology Letters 3, 706 708.

Handedness in Humans and Geladas

I thought I’d share a paper I wrote from last semester’s Comparative Psychology class on handedness in humans and geladas. Debating if I should actually follow through with this preliminary report and do some data collection. There is a YouTube video that accompanies this paper, which will appear on the bottom of the page.

Handedness can be defined as the unequal distribution of fine motor skills between the left and right hands. Simply put, handedness is the preference to use left, right or both hands when performing tasks. Humans are mostly right-handed across cultures. Here, I compare handedness in humans (Homo sapiens) to handedness in geladas (Theropithecus gelada).

Right-handedness is predominant across cultures in humans. About 85% to 90% of humans report themselves as right-handers (10). In studies of great apes, comparative analysis indicates that chimpanzees and bonobos exhibit population-level preference in right-handedness while gorillas and orangutans do not exhibit population-level preference in handedness (10). However, right-handedness seems to be uniquely human as no other primate species has such a clear bias (1, 13 & 14). The objective of this preliminary study is to elucidate whether geladas exhibit preference in handedness.

A male gelada at The Bronx Zoo.

Geladas are Old World Monkeys and can be found in the high plateau of North Central Ethiopia and Eritrea (9 & 2). Geladas are sometimes referred to as “bleeding heart monkeys” due to the presence of a naked, pink patch of skin on the chest of males and females that looks like an hourglass (2). They exhibit sexual dimorphism; males have manes and are slightly larger than females. The maximum lifespan of a gelada is about 19 years in the wild (5) and well over 30 years in captivity (9). Geladas are gramnivores; they are unique among primates because grass is their main food source but is occasionally supplemented by seeds, roots, and bulbs (3).

There are many definitions of handedness. Here, I define handedness as the preference of left, right or either hand when performing tasks. In humans, those who have a preference for using their right hand are right-handed while those that prefer using their left hand are left-handed. Those that prefer to use either hand when performing tasks are ambidextrous.

Approximate location of Broca's area and Wernicke's area. Photo from Wikipedia.

Handedness is due to the lateralization (asymmetry) of the brain hemispheres. Those that are right-handed have a more dominant left hemisphere, while those that are left-handed have a more dominant right hemisphere. In most humans, the left hemisphere of the brain is more dominant. The left brain hemisphere is also involved in language and is where Broca’s area and Wernicke’s area are located. Broca’s area is involved in speech production while Wernicke’s area is involved in language comprehension.

Right-handed preference is deep-seated in hominid evolution. Analysis of stone tools from Lower Pleistocene sites in Koobi Fora, Kenya and Middle Pleistocene sites in Ambrona, Spain showed that there is a consistent pattern of tools being produced by right-handed Homo habilis and Homo erectus (15). Preference for right-handedness may have existed as early as 1.4 to 1.9 million years ago, and might hint that the hominid brain had lateralized and was well on its way to becoming more specialized for different functions (15). Analysis of scratch patterns in incisors and canines from archaic humans (Sima de los Huesos in Atapuerca, Spain) and European Neandertals (Sima de los Huesos in Atapuerca, Spain and Vindija, Croatia) also showed that there was a persistent pattern of right handedness (6 & 7).

The prevalence of right-handedness in humans has a linear correlation with left hemisphere dominance (12). Since the left brain hemisphere plays an important role in language, brain lateralization leads to right-handedness. Thus, the prevalence of right-handedness in humans is a byproduct of human language.

The left-handed Ned Flanders from The Simpsons. Photo from SF Weekly.

The subjects for this study are from a captive population of geladas at The Bronx Zoo (Wildlife Conservation Society). There were 7 individuals present during the observations and all were male. Observations were done on two separate days between 12 P.M. and 3 P.M. The geladas were recorded using a video camera, and the recordings were later analyzed.

Geladas spend a significant amount of their time foraging (8). Site studies show that geladas spend 35.7% to 81.6% of their time foraging (8). There is a positive correlation between altitude and time spent foraging; more energy is burnt at higher altitudes, therefore more time is spent foraging (11).

A male gelada foraging with both hands.

My observations showed that geladas use either hand while foraging. They use either their left or right hands to pick up bunches of grass to eat. As my observation progressed, I became concerned that their repetitive motion of picking up grass and putting it in their mouths was not a sufficiently varied behavior to indicate handedness. Therefore, I also observed the geladas grooming.

A female gelada grooming herself.

There are two types of grooming in geladas: autogrooming (self grooming) and allogrooming (social grooming). Grooming is not only important for hygienic reasons but also important for strengthening social bonds (4). A study by Dunbar suggests that the major reason for grooming is the satisfaction of physical contact between the groomer and the individual being groomed (4).

From my observations, allogrooming starts with the individual being groomed initiating eye contact with the groomer. Then, the individual lies down and presents the area that needs to be groomed. Sometimes, a groomer simply approaches the individual they want to groom and starts grooming them. My observations showed that there is also no preference for which hand is used by geladas during grooming. The geladas used either hand for both autogrooming and allogrooming. The decision to use their left or right hand seemed to be determined by the area of the body that needed grooming.

From my observations, it seems that the geladas use either hand for foraging and grooming. The geladas at The Bronx Zoo seem to exhibit ambidexterity because they have no preference for their left or right hand, unlike humans who are predominantly right-handed.

Handedness is correlated with brain hemisphere dominance. For most humans, the left brain hemisphere is dominant and is also involved in language. Thus, the prevalence of right-handedness is a byproduct of human language. None of the geladas I observed at The Bronx Zoo exhibited preference for handedness. This is probably due to the fact that geladas do not have language; therefore, their left brain hemisphere is not dominant and does not lead to right-handedness. Besides foraging and grooming, more behavioral repertoire should be used in future analysis to further elucidate the preference in gelada handedness.









 References

 1. Cashmore, L., Uomini, N., & Chapelain, A. (2008). The evolution of handedness in humans and great apes. Journal of Anthropological Sciences, 86, 7-35.

 2. Dunbar, R.I.M., &; Dunbar, P. (1975). Contributions to Primatology: Social Dynamics of Gelada Baboons (Vol. 6). Basel, Switzerland: S. Karger AG.

 3. Dunbar, R.I.M. (1984). Reproductive Decisions. Princeton, New Jersey: Princeton University Press.

 4. Dunbar, R.I.M. (2008). The social role of touch in humans and primates: Behavioural function and neurobiological mechanisms. Neuroscience and Biobehavioral Reviews, 34(2), 260-268.

 5. Falk, D. (2000). Primate Diversity. New York and London: W.W. Norton & Company.

 6. Frayer, W.D., Fiore, I., Lalueza-Fox, C., Radovčić J., & Bondioli, L. (2010). Right handed Neandertals: Vindija and beyond. Journal of Anthropological Sciences, 88, 113-127.

 7. Frayer, W.D., Lozano, M., de Castro, J.M.B., Carbonell, E., Arsuaga, J.L., Radovčić J., Fiore, I., & Bondioli, L. (2011). Laterality: Asymmetries of Body, Brain and Cognition, doi:10.1080/1357650X.2010.529451

 8. Gron, KJ. (2008, September 3). Primate Factsheets: Gelada baboon (Theropithecus gelada) Taxonomy, Morphology, & Ecology. Retrieved May 11, 2011, from www.pin.primate.wisc.edu/factsheets/entry/gelada_baboon

 9. Hiller, C. (2000). "Theropithecus gelada" (On-line), Animal Diversity Web. Retrieved May 11, 2011, from www.animaldiversity.ummz.umich.edu/site/accounts/information/Theropithecus_ gelada.html

10. Hopkins, W.D. (2006). Comparative and Familial Analysis of Handedness in Great Apes. Psychology Bulletin, 132(4), 538–559.

 11. Iwamoto, T., & Dunbar, R.I.M. (1983). Thermoregulation, Habitat Quality and The Behavioural Ecology of Gelada Baboons. Journal of Animal Ecology, 52, 257-366.

12. Knecht, S., Dräger, B., Deppe, M., Bobe, L., Lohmann, H., Flöel, A., Ringelstein, E.-B., & Henningsen, H. (2000). Handedness and hemispheric language dominance in healthy humans. Brain, 123 (12), 2512-2518

13. McGrew, W.C., & Marchant, L.F. (1997). On the other hand: Current issues in and meta-analysis of the behavioral laterality of hand function in nonhuman primates. American Journal of Physical Anthropology, 104(25), 201-232.

 14. Steele, J. & Uomini, N. (2009). Can the Archaeology of Manual Specialization Tell Us Anything About Language Evolution? A Survey of the State of Play. Cambridge Archaeological Journal, 19, 97-110.

15. Toth, N. (1985). Archaeological Evidence for Preferential Right-Handedness in The Lower And Middle Pleistocene, and Its Possible Implications. Journal of Human Evolution, 14(6,) 607-614.

The Menstruation Story

In keeping with yesterday's post on sexual maturation, here's an interesting find from YouTube. The Menstruation Story was produced by Disney circa 1946. Quite an interesting video, I might say. With interesting take on the video by Shameless and NYmag.

Having Brothers Delays Menstruation and Sexual Activity in Sisters

Hey girls, your brother will not only pull out your Barbie's head but he will also delay your sexual maturation as well ... allegedly. A interesting study by two behavioral ecologists (Milne & Judge, 2010) on contemporary western society of Australian adults found that:

Girls with older brothers experience a delay in menstruation.
Girls with older brothers (but with no older sisters) started their menstruation at a mean age of 13.6 years while girls with older brothers and older sisters started their menstruation at a mean age of 13.3 years. Girls with no older brothers (with or without older sisters) started their menstruation at a mean age of 12.7 years. The more older brothers the girls had, the older they were when they started their periods. However, the age of the brothers does not effect the results.

Girls with younger brothers experienced a delay in first sexual activity.
Girls with one or more younger brothers experienced their first sexual activity up to two years later than girls without any younger brothers.

Neither younger nor older brothers influenced the fitness of their sisters. 
Brothers do not affects number of pregnancies, number of children, age at first pregnancy or the firstborn of their sisters.

It is thought that having boys in subsistence and preindustrial societies require more resources than girls, therefore imposing a constraint on lifetime reproductive success. Results from Milne & Judge (2010) were unusual for a society that has plenty of resources because it shows evidence that having brothers negatively affect their sister's sexual maturation. However, having brothers do not influence the reproductive fitness of their sisters. The authors posit that brothers in contemporary Australian are not associated with reproductive fitness due to their sisters having a long period of independence before child bearing. Dr. Judge said that she prefer not to speculate too much of the study as the study was very basic and straightforward. She emphasized that the delay in sexual maturation should not be interpreted as something negative.

Possible reason why younger sisters are experiencing a delay in first sexual activity.

Important to note that the study interviewed only 273 (n) adults between the age of 18 - 75. Out of the total 197 are females and 76 are men. It would be interesting to see results of the study from a bigger sample size because the study essentially represents the western society of Australia (N) as a whole, so the sample size (n) should be bigger. I don't know off hand the population size of western society of Australia, but the Australian population is currently 22,434,156 (current as of August 24, 2010 from Australian Bureau of Statistics). So I would be interested to see if the trend holds up to a bigger sample size, where (n) is at least over 1000. Also, would sisters of twins (with younger twin brother or older twin brother) exhibit the same delay in sexual maturation as well?

References:
Milne, F.H. Judge, D.S. 2010. Brothers delay menarche and the onset of sexual activity in their sisters. Proceedings of The Royal Society B DOI: 10.1098/rspb.2010.1377

Edwards, L. 2010. Having brothers delays sexual maturation in women. Physorg.com Retrieved August 23, 2010 http://www.physorg.com/news201419637.html

Sexual And Natural Selection: Why Humans Are Still Evolving

Comparative photo between a masculine-looking (left) and feminine-looking (right) male. Photo from Dienekes' Anthropology Blog.

On Dienekes' Anthropology Blog, he shares with us a study on the correlation between female mate choice (sexual selection) and national health index (DeBruine et al., 2010). Female tend to prefer more masculine-looking males in countries where the national health index is low. Consequently, females tend to prefer more feminine-looking males in countries where the national health index is high. Head over to Dienekes's blog to read about his blog post, "Preference for masculine/feminine-looking men and national health".

With natural selection at work, females are predicted to be much shorter and stouter in the future. Photograph by Hans Neleman/ Getty on Macleans.ca

Also read about "Evolution favours shorter and heavier women—like it or not", an article that foresees the evolution of females to be that of much shorter and stouter. Stephen Stearn, professor of evolutionary biology at Yale University thinks that humans continue to evolve even when we're in a post-industrial society. While there are no large-scale genetic changes, Stearn believes that natural selection is still at work.

“One [could express] the result as: women are going to get shorter and fatter,” he explains. But he prefers a different bent: “There is natural selection against women being slender.” Stearns’s work shows that plumper, shorter women tend to bear more children—who carry on those same traits. His analysis drew on data from the Framingham Heart Study: a survey, begun in 1948, that collected medical information from 5,209 subjects, and monitored them and their offspring for 60 years. 

The weight part of the equation, says Stearns, is straightforward: “A woman has to have about 20 per cent body fat to ovulate and conceive.” But he admits that he “can’t give a good explanation of why they are getting shorter.” A separate study by Open University’s Daniel Nettle found that shorter women are more likely to be in long-term, offspring-producing relationships—perhaps, he hypo thesized, because men evolved to disfavour tall women, who tend to reach puberty later. 

Modern Humans Are Still Evolving But Will Modern Men Get Wimpier?

Two interesting articles that went into my inbox today: Modern man a wimp says anthropologist and Darwin Lives! Modern Humans Are Still Evolving.

A cover illustration from Australian anthropologist Peter McAllister's new book entitled "Manthropology" and sub-titled "The Science of the Inadequate Modern Male." Photo from REUTERS/Hachette Publishing/Handout.

Modern man a wimp says anthropologist  from Reuters, summarizes Peter McAllister's book Manthropology: The Science of the Inadequate Modern Male. Using various data from Neanderthals and ancient aboriginal populations, McAllister concludes that modern men are inferior than their predecessor in running, jumping, and even sheer brute. "Any Neanderthal woman could have beaten former bodybuilder and current California governor Arnold Schwarzenegger in an arm wrestle", McAllister said. John Hawks from John Hawks Weblog has a lot to say about this in his post Is modern man a "wimp"? I think Hawks is spot on with his post.

The Time article, Darwin Lives! Modern Humans Are Still Evolving, is about a study in a contemporary Massachusetts population led by Stephen Stearns and his team of scientists from Yale University. Using correlations between women's physical characteristics such as height, weight, blood pressure, and cholesterol levels with the numbers of offspring produced, they found that "stout, slightly plump, but not obese" women tend to have more offspring as oppose to women with very low body fat count, as well as women with lower blood pressure and lower cholesterol levels.

Stearns explains that women with very low body fat count, low blood pressure and low cholesterol levels do not ovulate. Ovulation is, of course, when the matured ovarian follicle ruptures and discharge an ovum (or the egg). While human females ovulate about once a month, female chickens ovulate once a day. Of course, we refer to chicken ovum as chicken eggs.

Stearns and his team thinks that the characteristics for producing maximum offspring (stout, slightly plump, higher blood pressure and cholesterol levels) were passed down from mothers to daughters. Separating social and cultural factors using statistical analysis, Stearns and his team were able to conclude that these characteristics were passed down genetically. "Variations in reproductive success still exist among humans, and therefore some traits related to fertility continue to be shaped by natural selection" Stearns says. So women who have more children are more likely to pass down these traits to their offspring.

It explains the notion that modern humans are still evolving because variation in reproductive success means that there are selective pressure that favor certain traits. Interesting to note that while fertility is being shaped by natural selection (as per Stearn and his team's study), artificial selection is also shaping the width of female pelvis and the average brain size of infants being born. Mothers with a narrow birth canal (smaller pelvis size) puts both her and her infant in jeopardy during childbirth. The infant will be stuck in the birth canal due to restricted space. An infant with a larger than average brain size will also get stuck in the birth canal. Both scenarios will likely kill the infant and mother. However the advent of Caesarean section negates the restriction of a narrow birth canal and allows infant with larger brain size to be born.

So, we can see that modern humans are evolving through variation in reproductive success, female pelvis size and average infant brain size is also evolving through artificial selection though it is too early to say which direction the selection is favoring.

When It Comes To Being The "Missing Link", Ida -- You Are NOT The Candidate

Main slab of Darwinius masillae (specimen PMO 214.214), new genus and species, from Messel in Germany. Photo from Wikipedia.

Ida or "Aunt Ida" as many might recall from this summer of craziness sent shock waves around the nation as it was herald the missing link between prosimians and anthropoids (primates and human). Deserving of its own genus, Ida was given the name Darwinius masillae by Franzen et al. (2009) as they describe this specimen in their paper. Darwinius to celebrate the bicentennial celebration of Darwin's claim to fame "Origin of Species" and masillae for the location where Ida was discovered (Messel Pit, Germany).


Complete Primate Skeleton from the Middle Eocene of Messel in Germany: Morphology and Paleobiology was published this summer. Soon thereafter, the general public expressed sheer amazement and curiosity, especially the press who were all too excited to report such breaking news. Hence, "Aunt Ida" became synonymous with "Ida" due to the general public's warm family reception. Others, such as the religious nuts were quick to point out that Ida was just another god(s) creation and the notion of a "missing link" is preposterous. Even Google participated in this frenzy, much to the chagrin of religious right-wing, featuring Ida in Google's logo on May 20th, 2009.

Ida as Google icon. Illustration from Google.

American Museum of Natural History soon announced that you can see Darwinius masillae in their Extreme Mammal exhibit (which I later find out that it is just a cast). The Discovery Center at Times Square also got into the game by exhibiting Darwinius masillae. All these publicity and attention makes one wonder. Is this just a publicity stunt on a premature discovery and discussion? Not to mention all the money they made from this discovery "that changes everything".

I, for one, was on the fence. While I was amazed and interested with the discovery, all these publicity stunt just does not bode well with me. I chose not to write about Ida's discovery in this blog, not because I was too lazy to add my one cent but rather I'd prefer to sit back and listen to all the discussions. One, I'm not a paleontologist nor am I an expert on skeletal morphology. I'd love to know if  Darwinius masillae actually groomed each other though.

So what made me wrote this blog entry? My inbox is filled with new articles about Darwinius masillae but this time disproving its role as the missing link. A new paper, published by Seiffert et al. (2009), concludes that Darwinius masillae is closely related to the genus Afradapis (an adapiform or adapoid). They also conclude that Darwinius masillae sits on the dead end of the evolutionary branch, without leaving any descendants let alone being the missing link for humans. Thus the title "missing link" is not befitting of this 47 million year old Eocene primate.

Phylogenetic position of the adapiforms Afradapis and Darwinius within primates. Photo from Wired.

So now that you have both sides of the story, what's your opinion on  Darwinius masillae? I'm betting my bananas that Darwinius masillae is just another product of a highly publicized discovery. Not to undermine the important discovery of this new genus but quoting my undergraduate professor, Dr. Sara Stinson, "There is no such thing as a missing link. We know where everything goes". She's right ... in fact the idea of a "missing link" is just an agent used by those who do not believe in evolution. You know, like the idea of Crocoduck (Hint: Kirk Cameron).

Further readings:
Bone Crunching Debunks ‘First Monkey’ Ida Fossil Hype from Wired.
So Ida's not the "missing link": questions and answers with Erik Seiffert from Times Online.
'Eighth wonder' Ida is not related to humans, claim scientists from Guardian.co.uk.
Darwinius on Wikipedia.

References:
Franzen, JL. Gingerich PD. Habersetzer, J. Hurum, JH. von Koenigswald, W. Smith, BH. 2009. Complete Primate Skeleton from the Middle Eocene of Messel in Germany: Morphology and Paleobiology. PLos ONE 4(5): doi:10.1371/journal.pone.0005723.

Seiffert, ER. Perry, JMG. Simons, EL. Boyer, DM. 2009. Convergent evolution of anthropoid-like adaptations in Eocene adapiform primates. Nature 461, 1118-1121 doi:10.1038/nature08429.

The Uncanny Valley: Humans and Macaques

The uncanny valley hypothesis posits that when robots and other human facsimiles look and act almost like humans, it causes a response of revulsion among human observers. The "uncanny valley" refers to the dip in the graph of the positivity of human reaction as a function of a robot and other human facsimiles's life-likeness (see below).

Hypothesized emotional response of human subjects is plotted against anthropomorphism of a robot, following Mori's statements. The uncanny valley is the region of negative emotional response towards robots that seem "almost human". Movement amplifies the emotional response. Photo from Wikipedia.

It is the reason why we prefer cartoon characters than CGI characters that look realistic. For example, you are more likely to like the Homer Simpson on the left than the one on the right.

Read about the uncanny valley hypothesis here.

Now this is the interesting part. Using long-tailed macaques (Macaca fascicularis) as test subjects, Steckenfinger and Ghazanfar (2009) found that these monkeys' visual behavior actually fell into the uncanny valley, which mirrors the behavior of humans. These macaques looked longer at real faces and unrealistic synthetic faces than realistic synthetic faces.

The unrealistic synthetic faces, realistic synthetic faces and real faces. Actual images used in Steckenfinger and Ghazanfar's experiment.

The authors did not conclude why the visual cues of these macaques fall into the uncanny valley, though they did suggest that it has an evolutionary basis.

Remember the picture above? If not, read my blog entry on Contagious Yawning in Chimpanzees. I see you yawn. I wonder if those chimpanzees will yawn if given more realistic synthetic faces.

Reference:
Steckenfinger, SA. Ghazanfar, AA. 2009. Monkey Visual Behaviors Falls Into The Uncanny Valley. Proceedings of the National Academy of Sciences Retrieved October 15, 2009, from http://www.pnas.org/content/early/2009/10/07/0910063106.full.pdf+html [10.1073/pnas.091006310]

Can I See Your Fingers Please?

That is what University of Liverpool's Emma Nelson probably would have said if she were to meet our hominan ancestors in person. Known to hold true in anthropoids (humans, apes and monkeys), the index (second digit) to ring (fourth digit) fingers ratio or 2D:4D is an indication of how much an individual were exposed to androgen (such as testosterone) in the womb. The more androgen you are exposed to, the longer the ring fingers are (and the shorter the index fingers are compared to the index fingers).

Photo of a human's left hand. From left to right: thumb, index, middle, ring and little finger. Photo modified from Wikipedia.

Nelson et al. believe that a high ratio (longer index finger, shorter ring finger) suggests monogamy (or pair-bonded) while a low ratio (shorter index finger, longer ring finger) suggests polygamy (or non pair-bonded). Simply put, individuals with high androgen level is likely to be non pair-bonded and the telltale sign is in the index and ring fingers. Also, some controversial studies had suggested that both men and women who receive high levels of androgen in the womb are more likely to be stronger, faster, and more sexually competitive.

Nelson and her researchers recently looked at the fossils of two Neandertals and one Australopithecus afarensis with complete index and ring fingers to determine their 2D:4D. They found that Neandertals had long ring fingers, suggesting that they were polygamous just like modern day primates that live in groups. A. afarensis on the other hand, had long index fingers. Nelson is puzzled by this discovery. "These were small creatures that probably lived in groups and were being eaten by predators. How do you keep from mating with different members of the group?", she said.

Indeed it does not make sense for A. afarensis to be monogamous if they live in groups. Notice that Nelson et al. only used one A. afarensis fossil to get the 2D:4D. Perhaps it is not their fault that only one A. afarensis specimen had complete index and ring fingers but such are the dilemma of using fossil specimens to generalize a whole species.The result might just be a statistical outlier. However, I can't speculate the result or the implications but anyone that are familiar with statistical data knows that a small sample size leads to a higher sampling error. Also what would a 2D:4D = 1 (same index and ring finger length) be?

Interesting enough, John Hawks at John Hawk's Weblog mentioned the correlation of 2D:4D with male homosexuality (Robinson and Manning, 2000). I would know about this. In fact, my 2D:4D is indeed low.  Robinson and Manning predicted right! Maybe ...

I do find both Nelson et al. and Robinson and Manning (2000) research interesting but I would like to stress that the results are mere predictors and correlations. Take it with a grain of salt. Don't go measuring 2D:4D of your future spouse, boyfriend or girlfriend and accuse them of not being monogamous or a homosexual.

Emma Nelson and her team presented their research at this year's Society for Vertebrate Paleontology meeting held in Bristol, United Kingdom. Read more about Emma Nelson's research.

References:

Reilly M. 2009. Human Ancestors Conflicted on Monogamy. Discovery News. Retrieved September 25, 2009, from http://dsc.discovery.com/news/2009/09/24/human-monogamy.html

Robinson SJ. Manning JT. 2000. The ratio of 2nd to 4th digit length and male homosexuality. Evolution and Human Behavior 21(5): 333-345. [doi:10.1016/S1090-5138(00)00052-0]

Frans de Waal: A Helping Hand Or A Stab In The Back - Which Is More Human?

Dr. Frans de Waal will be having a lecture and book signing tomorrow (Thurs, Sept 24) , 7pm at The Kaye Playhouse at Hunter College. For all you Facebook users, Dr. De Waal has a Facebook fan page as well! You really should go become his "fan" on his page. Really.

Below is the description from Hunter College's website:

Thursday, September 24, 2009
7:00 PM
A Helping Hand Or A Stab In The Back - Which Is More Human?

World-renowned primatologist Dr. Frans de Waal will discuss his ground-breaking book The Age of Empathy: Nature's Lessons for a Kinder Society.

An exploration of the origins of human morality that challenges many of our most basic assumptions, The Age of Empathy has been written by one of the world's leading primatologists, Dr. Frans de Waal, called one of the world's 100 most influential people by Time magazine and the winner of the Los Angeles Times Book Award. De Waal's newest book looks at the question of whether competitive, selfish behavior is really "instinctive" and "natural," an outgrowth of evolution and the survival of the fittest. However, using research from anthropology, psychology, neuroscience, and animal behavior, de Waal argues that humans are equally hard-wired for empathy. We are, he says, group animals - cooperative, sensitive to injustice, and mostly peace-loving - just like other primates, elephants, and dolphins. De Waal's findings have profound implications for politics, office behavior - and perhaps our very survival.

The Kaye Playhouse at Hunter College
(68th Street between Lexington and Park Avenues)

Program is free and open to the public.
To RSVP, click here or call (212) 772-4007.

Contagious Yawning in Chimpanzees

Animation of chimpanzee yawning from Emory University. Illustration from BBC News.

I'm sure we are all familiar with this scenario: Someone yawns and we would "catch" it or vice versa. This is the phenomenon of contagious yawning.

A new paper from The Proceedings of The Royal Society "Computer animations stimulate contagious yawning in chimpanzees" suggests that the phenomenon of contagious yawning and empathic response to animation occurs in chimpanzees. Computer animations of yawning chimpanzees (see illustration above) can be use to stimulate contagious yawning in chimpanzees. Previous researches have documented contagious yawning in chimpanzees through video-recorded footage.

Dr. Matthew Campbell, lead author of the paper from Emory University's Yerkes National Primate Research Center said that they would also like to learn more about behaviors that are related to empathy such as consolation (when an individual does something nice to the victim of aggression). They want to know if individuals that are good contagious yawners are also good consolers. Understanding how chimpanzees empathize and imitate animations can help us understand how we, as human beings, empathize and imitate animations as well, said Dr. Campbell.

Homo floresiensis Walked Out of Africa

Skull of LB1 (Homo floresiensis, or the hobbit). Photo from Science Museum

New analysis by a team led by Australian National University doctoral student Debbie Argue showed that Homo floresiensis, nicknamed hobbits, were early hominin and walked out of Africa to Flores. Their findings supports the argument that Homo floresiensis had a unique wrist anatomy that originated from a lineage that lived long before the common ancestor of Homo sapiens and Neanderthals.

With Mike Moorwood from University of Wollongong and Thomas Sutikna from Indonesian Center for Archaeology, Debbie Argue compared 60 skulls and skeletal features from two individual hobbits to those of hominins, chimpanzees and gorillas using cladistic analysis. The result shows that Homo floresiensis "probably took one of two evolutionary paths from Africa to Flores. One began 1.66 million years ago, the other 1.9 million years ago".

Read more here: Hobbits Walked Out of Africa

Humans Evolved From Tree Climbers

A research from Duke University by Daniel Schmitt, associate professor of evolutionary anthropology, and Tracy Kivell, a post-doctoral research associate, shows that human evolved from tree climbing ancestors, not from knuckle-walkers. Schmitt and Kivell examined and compared the wrist bones of humans and African apes. Their research, "Independent evolution of knuckle-walking in African apes shows that humans did not evolve from a knuckle-walking ancestor", was published in the Proceedings of the National Academy of Sciences on August 10th, 2009.

They also found that knuckle walking evolved at least two different times; gorillas fundamentally knuckle walk differently than chimpanzees and bonobos.

Kivell and Schmitt think this suggests independent evolution of knuckle-walking behavior in the two African ape lineages.

Some scientists point to features in the human anatomy as our own vestiges of a knuckle-walking ancestry. One notable example is the fusion a two wrist bones that could provide us extra stability, a feature we share with gorillas, chimps and bonobos.

But some lemurs have that feature too, and they do a variety of different movements in the trees but do not knuckle-walk, Kivell said.

Altogether, the evidence leans against the idea that our own bipedalism evolved from a knuckle-walking ancestor, the pair wrote. "Instead, our data support the opposite notion, that features of the hand and wrist found in the human fossil record that have traditionally been treated as indicators of knuckle-walking behavior in general are in fact evidence of arboreality."

In other words, a long-ago ancestor species that spent its time in the trees moved to the ground and began walking upright.

There are no fossils from the time of this transition, which likely occurred about seven million years ago, Kivell and Schmitt said. But none of the later fossils considered to be on the direct human line were knuckle-walkers.

Read more on Science Daily: Bipedal Humans Came Down From The Trees, Not Up From The Ground

New Study Suggests That Humans are More Closely Related to Orangutans, Not Chimps

Sorry, been traveling here and there lately so don't really have time to post blog updates. Found this interesting article on EurekAlert!

A new study suggests that humans share a common ancestor with orangutans, not chimpanzees according to shared physical characteristics.

Comparing physical characteristics instead of DNA, researchers Jeffrey H. Schwartz and John Grehan found that humans shared 28 unique physical characteristics with orangutans, share only two features with chimpanzees and seven with gorillas. Humans share seven characteristics with all three apes (chimpanzees, gorillas, and orangutans). Gorillas and chimpanzees shared 11 unique characteristics.

Schwartz and Grehan proposed to have a new "grouping" or classification for humans, orangutans and last common ancestor call "dental hominoids" because they all share similar thick-enameled dental.

Read more about this study at EurekAlert! Humans related to orangutans, not chimps, says new Pitt, Buffalo Museum of Science study.

The Face Of The First European

The face of the first European, reconstructed by forensic artist Richard Neave. Photo from Telegraph.

Using the incomplete skull and jaw bone in a cave in the southwest of the Carpathian Mountains in Romania, scientists had revealed for the first time the face of the first European.

Scientists doesn't know if this modern human is a male or a female but using radiocarbon analysis they found that this individual lived around 34,000 to 36,000 years ago. Around this time, Europe is home to both Neanderthals and modern humans. Modern humans first arrive to Europe from Africa.

The skull of this individual is human-like, though there are also some archaic traits such as large molars. Some scientists speculated that this skull belongs to a Neanderthal and modern human hybrid though it was disproved by many experts.

Richard Neave, a forensic artist used clay to reconstruct this individual for a BBC program about the origins of the human race and evolution.

Walk Like A Modern Human: 1.5 Million-Year-Old Footprints Found In Ileret, Kenya

Fossilized footprints were found between two sedimentary layers in Ileret (Rutgers' Koobi Fora Field School), Kenya that dates back about 1.5 million-years-ago. These footprints show that its owner was walking upright, bipedally and the foot already had the anatomy like those of modern humans: relatively adducted hallux (big toe), medial longitudinal arch and medial weight transfer before push-off. The size of the footprints corresponds to the stature and body mass of Homo ergaster, an earlier version of Homo erectus (Bennett et al., 2009).

Cover of Science, 27 February 2009. Optical laser scan of early hominin footprints at Ileret, Kenya, color-rendered to illustrate depth; reds indicate areas of high elevation, blues lower elevation. The footprints are 1.5 million years old and were probably made by Homo ergaster/erectus. Two right footprints and a partial left are visible along with a range of animal prints. Image processing in Rapidform^TM: Matthew Bennett/ Bournemouth University.

These footprints are distinct from the "famous" Laetoli footprints, discovered by Mary Leakey in 1976 at Laetoli, Tanzania which dates to about 3.5 million-years-ago. The Laetoli footprints belong to Australopithecus afarensis and at least two individuals were present, walking side by side.

Laetoli footprints. Photo from www.pbs.com

The Ileret footprints are different and similar to the Laetoli footprints in many ways. Laetoli footprints are more ape-like, Ileret footprints are more human-like. Both, however, do not have an opposable toe like those of chimpanzees. Both footprints indicate that its owner was walking bipedally or has a bipedal gait.

Comparison between a chimpanzee footprint and Australopithecus afarensis (Laetoli) footprint. Photo of chimpanzee footprint from www.elucy.org and photo of Laetoli footprint from www.columbia.edu




Comparison between Homo ergaster (Ileret footprint) and modern human. Photo of Ileret footprint by Matthew Bennett from www.nationalgeographic.com

Read more on "Prints Are Evidence of Modern Foot in Prehumans" by John Noble Wilford.
Rutgers' Press Release: 1.5 Million-Year-Old Fossil Humans Walked on Modern Feet.

Citation:
Bennett MR. Harris JWK. Richmond BG. Braun DR. Mbua E. Kiura P. Olago D. Kibunjia M. Omuombo C. Behrensmeyer AK. Huddart D. Gonzalez S. 2009. Early Hominin Foot Morphology Based on 1.5-Million-Year-Old Footprints from Ileret, Kenya. Science 323 (5918): 1197 - 1201. [DOI: 10.1126/science.1168132]