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.

Keeping up with the Hominin

In less than a week, some of you will be shuffling back to school as Fall session begins. Every new semester, without a doubt, you'll be able to pick out the smart ass in the class. You know, the ones that sit in front of the class and always have their hands up when the professor asks a question (think Hermione Granger). But what if you are the smart ass? Have no fear, you're reading the right post.

"Hominin - the group consisting of modern humans, extinct human species and all our immediate ancestors (including members of the genera Homo, Australopithecus, Paranthropus and Ardipithecus)."

- Australian Museum.

A lot had happened this year with hominin research and some would redefine conventional understandings of this group. Below is a list of new studies that came out this year that I find quite interesting on hominin. Read up so you can show off in class with your knowledge of current hominin research. You know, just so you can make sure that your adjunct is really paying attention of what he/she is doing instead of begrudgingly teaching a class because he/she has to. Or maybe you have a geeky classmate you want to impress. Or if you're like me, you just wanna be the smartest in class because Asian Fail is not an option. So, enjoy ... and if they question you, tell them I said so.

Australopithecus africanus and Paranthropus robustus

• Male philopatry and female dispersal in both A. africanus and P. robustus. Is this a strategy to prevent inbreeding and mate choice by females? Ancient Hominid Males Stayed Home While Females Roamed, Study Finds

Paranthropus boisei

• Seems like we'll have to re-evaluate P. boisei's nickname, "Nutcracker Man". Recent study showed that P. boisei didn't eat nuts but instead used its big teeth to chew on grasses and sedges. No nuts for 'Nutcracker Man': Early human relative apparently chewed grass instead

From left to right: Comparison of upper jaw, P. boisei and H. sapiens. Photo from PhysOrg.

Homo erectus

• H. erectus were the first to controlled fire but it wasn't just used for warmth. New study shows that H. erectus were the first to cook their food (with fire) and process their food with tools. Homo Erectus Processed Food Like Humans, Harvard Scientists Say

• Stone artifacts, mostly flakes from stone tools, from the Dmanisi site in Georgia (the country, not the state) might suggests that H. erectus evolved outside of Africa. However, no conclusive evidence can be made due to the poor conditions of fossils found near these artifacts. Human ancestors in Eurasia earlier than thought

• H. erectus reached South Asia earlier than previously thought, between 1.5 to 1 million years ago according to Acheulean tools. Go east, ancient tool makers

• Findings from Solo River Terrace (SoRT) in Indonesia shows that H. erectus never coexisted with H. sapiens. Using three dating techniques: U-series, Electron Spin Resonance (ESR) and argon-argon, scientists found H. erectus went extinct between 143,000 to 550,000 years ago. H. sapiens are thought to reached Indonesia about 40,000 years ago. Human Ancestor Older Than Previously Thought; Finding Offers New Insights Into Evolution

An Acheulean hand ax found in India (South Asia) indicates that H. erectus moved to South Asia shortly after the invention of stone tools, around 1.6 million years ago. Photo from ScienceNews.

Homo neanderthalensis

• Neandertals probably died off because there were too many early humans to compete with. According to a statistical analysis, the Périgord region of southwestern France has the highest concentration of Neandertals and early humans. The ratio between Neandertal to early human was 1 to 10. There were just too many humans for Neanderthals to survive

• Mousterian culture might have lasted longer than previously thought and Neandertals might have spread as far as northern Russia in the mountains of Polar Urals, near the Arctic Circle. Last Neanderthals Near the Arctic Circle?

• Neandertals were predominantly right-handed, according to their teeth. Also, humans have been predominantly right-handed for at least 500,000 years. Neanderthal ancestors were mostly right-handed

Homo floresiensis (the Hobbits)

• The debate whether H. floresiensis is a separate species or just microcephalic H. sapiens continues on. New study shows that the measurement of the Hobbit skull is within the range of microcephalic H. sapiens. Taking the measure of a hobbit

From left to right: Homo floresiensis (LB1) and Homo sapiens.

Homo sapiens (early and modern humans)

• Early humans have been playing hanky panky with Neandertals and possibly the Denisovans. Proof? A toe bone and its DNA. Stone Age toe could redraw human family tree

• A particular segment of our X-chromosome were inherited from Neandertals. This supports the hypothesis that early humans interbred with Neandertal. However, only non-African humans have this segment. Confirmed: All non-African people are part Neanderthal

• Might not be a conscious decision, but apparently early humans that left Africa interbred with Neandertal to protect themselves against diseases. This is probably an unintended result more than an active thought process. First modern humans protected themselves against disease after leaving Africa by 'interbreeding with Neanderthals'

*Bouchra child, Homo sapiens*

• Dr. Harold Dribble and his team found the skull of "world's oldest human child" dated around 108,000 years old in Morocco and nicknamed it Bouchra. The boy died when he was 8 years old. This specimen has not been described in any scientific paper so watch out for it soon. World’s Oldest Child Found in Morocco

Unearthed finger bone points to the possible discovery of an unknown hominin

DNA analysis from a finger bone unearthed from Denisova Cave, Siberia might lead to the discovery of an unknown hominin. Dubbed "X-Woman", information from her mitochondrial DNA suggests that she shared a last common ancestor with modern human and Neanderthals about one million years ago.

Since Neanderthals and modern humans split at about 500,000 year ago, it suggests that she did not originate from that divergent. Instead, she represents an unknown hominin lineage, presumably an unknown migration out of Africa. "X-Woman" is too young to be a descendant of Homo erectus (which migrated out of Africa to Asia about two million years ago) yet too old to be a descendant of Homo heidelbergensis.
 

"Whoever carried this mitochondrial genome out of Africa about a million years ago is some new creature that has not been on our radar screens so far," said co-author Professor Svante Paabo, also from the Max Planck Institute for Evolutionary Anthropology.

Read more about this discovery on BBC News, DNA identifies new ancient human.

Said article can be found on Nature, The complete mitochondrial DNA genome of an unknown hominin from southern Siberia (Krause et al., 2010). Unfortunately I do not have access to said journal so if you have a copy I'd appreciate it A LOT if you can send it to me. Thanks Mark, for the pdf.

*Edit* Here's a pdf from Nature, Fossil finger points to new human species.

A New Homo Erectus Endocast From China (Zhoukoudian V)

A newly published paper, A new Homo erectus (Zhoukoudian V) brain endocast from China, by Wu et al. (2009) in Proceedings of The Royal Society B is available online for free. Here's the abstract:

A new Homo erectus endocast, Zhoukoudian (ZKD) V, is assessed by comparing it with ZKD II, ZKD III, ZKD X, ZKD XI, ZKD XII, Hexian, Trinil II, Sambungmacan (Sm) 3, Sangiran 2, Sangiran 17, KNM-ER 3733, KNM-WT 15 000, Kabwe, Liujiang and 31 modern Chinese. The endocast of ZKD V has an estimated endocranial volume of 1140 ml. As the geological age of ZKD V is younger than the other ZKD H. erectus, evolutionary changes in brain morphology are evaluated. The brain size of the ZKD specimens increases slightly over time. Compared with the other ZKD endocasts, ZKD V shows important differences, including broader frontal and occipital lobes, some indication of fuller parietal lobes, and relatively large brain size that reflect significant trends documented in later hominin brain evolution. Bivariate and principal component analyses indicate that geographical variation does not characterize the ZKD, African and other Asian specimens. The ZKD endocasts share some common morphological and morphometric features with other H. erectus endocasts that distinguish them from Homo sapiens.

Tim Jones from Anthropology.net has a great write up about the paper, A New Homo erectus (Zhoukoudian V) Brain Endocast From China – Free to Access.

"Whence Homo floresiensis? Clues From The Brain." By Dean Falk, Florida State University

During the 7th Human Evolution Symposium, Hobbits in the Haystack: Homo floresiensis and Human Evolution at Stony Brook, Dean Falk presented her lecture entitled "Whence Homo floresiensis? Clues from the Brain". She concluded that Homo floresiensis is a species of its own, LB1 did not suffer from microcephaly and Homo floresiensis is not a diminutive form of Homo erectus or Homo sapiens.


Falk commented that LB1 had a small-sized but "fancy" brain and that there was a "global reorganization" of the brain. Comparing LB1 with 9 modern human microcephalic skulls, Falk came to the conclusion that LB1's skull is nothing alike from a microcephalic and that LB1 was not a microcephalic.

A computer image depicts the brains (red) of a microcephalic modern human (left), and the fossil specimen of the Homo floresiensis (right). Microcephalics are also called "pinheads" due to the "pin-like" shape of their frontal lobe. Photo from National Geographic.

The shape of LB1's brain matches closely to those of Homo habilis. Falk thinks that LB1 might share ancestral history with Homo habilis and australopithecines. This is due to the characteristics that are found in LB1's brain.


Falk ended her lecture by talking about "insular dwarfism". Brain size and relative body size shrinks proportionately in the case of insular dwarfism. In the case of Homo floresiensis, its brain size did not shrink proportionately with its relative body size when compared to Homo erectus or Homo sapiens (based on the argument that Homo floresiensis is a diminutive version of Homo erectus or Homo sapiens)

Hobbits In The Haystack: Homo floresiensis And Human Evolution

The 7th Human Evolution Symposium, Hobbits in the Haystack: Homo floresiensis and Human Evolution was held yesterday at Stony Brook. Turnouts were great despite damp and rainy weather. Convened by Richard Leakey, the symposium was an all day event where researchers share their findings on Homo floresiensis. The highlight of the symposium is the first ever complete cast of LB1, or Flo and a host of Homo floresiensis researchers.

The symposium ended with questions and issues for discussion by Richard Leakey. Then, the floor was opened for general Q&A session with the panel. I will write about each presentations tomorrow, I'm currently swamped with school work!

"Accepting it (Homo floresiensis) will require us to rewrite the textbooks." - William Jungers, Stony Brook University.

Here is a list of topic presented by speakers during the symposium:

"Hobbits in context: life, times and death of Homo floresiensis" by Michael J. Morwood, University of Wollongong, Australia.

"Digging up Hobbits: The Excavations at Liang Bua" by Thomas Sutikna, National Research and Development Centre for Archaeology, Indonesia.

"Stone Tools and Hominins on Flores" by Mark Moore, University of New England, Australia.

"Whence Homo floresiensis? Clues from the brain." by Dean Falk, Florida State University.

"Her Teeth Were Sharp, Her Gums Were Raw, and Spit Was Dripping From Her Jaw: The Little Things That Make Us Human" by Peter Brown, University of New England, Australia.

"Why the Tiny Wrist Bones of a Hobbit Tell Us So Much About a Big Chapter in Human Evolutionary Theory" by Matthew Tocheri, Smithsonian Institution.

"The Hobbit Shrugged: The Shoulder of Homo floresiensis and its Implications For Human Evolution." by Susan Larson, Stony Brook University.

"Can Island Dwarfing Explain Hobbit Body Size and Shape?" by William Jungers, Stony Brook University.

"Virtual Hobbits and Health in Homo floresiensis" by Charles Hildebolt, Washington University in St. Louis.

A list of what Richard Leakey commented and asked during the symposium:

We should be careful when using Lucy as model for comparison because Lucy is not representative of the genus Australopithecine in general.

We don't have Homo erectus feet in our fossil record. The fossilized foot prints that were found in Ileret, Kenya has been suggested that it was left behind by Homo ergaster, an earlier version of Homo erectus.

There should be more discussion on the types of dating methods used on Homo floresiensis and the artifacts found in association with it.

There should be more discussion and research to link lithic materials to the Hobbits, or Homo floresiensis.

What were the geographic isolation of Flore? How did the Hobbits ended up in Flores?

Were there large carnivores in Flores or lack thereof? Hobbits have ape-like feet that were built for walking but not for running. Did they survive despite that because they have no need for speed to get away from predators?

Karen Baab and Kieran McNulty: Modern Procrustes

I found this while searching for news articles on "The Hobbits" or "Homo floresiensis". Sometimes taxonomy gives me headaches. I don't know why humans are so obsessive compulsive about putting things in categories. I guess that same reason is why I put labels on my blog posts.

Anthropologists Karen Baab from Stony Brook University Medical Center and Kieran McNulty from University of Minnesota published "Size, shape, and asymmetry in fossil hominins: The status of the LB1 cranium based on 3D morphometric analyses" in the Journal of Human Evolution last July. Click for .pdf version of the article.

Photo from the Science Museum

Using principal components analysis in shape space and in Procrustes form space, they shrank skulls of modern humans, fossil hominins and apes proportionate to their body so that they can use these new simulated models to compare LB1's skull. They found that LB1's skull closely resembles those of the genus Homo, too different to be those of modern human but close enough to be related to Homo erectus or something more primitive.

"You can't just make things bigger or smaller," McNulty explains. "When things change size, they need different mechanical properties." Or, there could be certain spatial requirements for the brain. A host of factors determine the proportions of the "shrunken" skull.

They concluded from their study that LB1 was more primitive than those of the Asian Homo erectus and perhaps LB1 (Homo florensiensis) was a descendent of a hominin population that predates Asian Homo erectus which underwent a process of size reduction.

Read the press releases from University of Minnesota and Stony Brook University.

I think a lot of people see LB1 as modern human because the skull looks like a shrunken modern human skull. They try to explain why LB1 is so small in stature, from microcephaly to dwarfism. But sometimes looks can be deceptive. LB1 might look like a modern human but it's not. I think that Homo floresiensis is a species of its own and it seems that more and more evidence is surfacing to prove so.

Questioning The "Out-Of-Africa" Model

The "Out-Of-Africa" Model is something that all Biological Anthropology students get drilled into their heads in Anthropology 102. Some Homo erectus migrated out of Africa to different regions. Archaic Homo sapiens then evolved from Homo erectus. Archaic Homo sapiens from Africa migrated out and displaced other archaic Homo sapiens from different regions. These archaic African Homo sapiens then evolved and became anatomically modern humans (Homo sapiens sapiens) Academically it is also call the recent single-origin hypothesis (RSOH), the Replacement Hypothesis or the Recent African Origin (RAO) model. These hypotheses came from the discovery of mitochondrial DNA, a kind of DNA that's only passed down by females to their offspring. Tracking this mitochondrial DNA, we can all draw our lineage back to a single female aptly named Mitochondrial Eve. Read about the "Out-Of-Africa" Model from a wiki entry.

The "Out-Of-Africa" Model. Illustration from Raritan Valley Community College

Well all that is fine and dandy. We were even told that the "Multiregional" Model is pretty much not accepted in academia nowadays. However, this dude begs to differ.

The "Multiregional" Model. Illustration from Wikipedia.

Akhil Bakshi, an Indian "explorer" led a multidisciplinary Gondwanaland Expedition across the 17 countries of South Asia, West Asia and Africa. He questions the "Out-Of-Africa" Model and in favor of the notion that anatomically modern humans were the byproduct of interbreeding between archaic Homo sapiens across different regions. He is actually in favor of the "Multiregional" Model.

Read his article here (text or .pdf). What do you think?

The Evolution Of Race: Homo Erectus?

The 2002 discovery of a Homo erectus fossil found in a marble quarry in Denizli, Turkey was a 20 to 40-year-old dark skinned male with signs of tuberculosis, according to Hurriyet news.

"The 500,000 years old skull fossil is expected to provide hints to the science world on the first humans’ migration and spreading on earth. The fossil agrees with the thesis of mankind originating from Africa", said Mehmet Cihat Alçiçek, assistant professor at the Geological Engineering Faculty in Pamukkale University.

It is documented that as modern humans moved north or south from the equator, their skin color becomes lighter. The further north or south from the equator, production of melanin (skin pigment) in the body decreases gradually so that enough vitamin D can be absorbed from sunlight. This Homo erectus fossil was a dark-skinned male, presumably had migrated out of Africa to Turkey. He had suffered from tuberculosis, a disease susceptible from vitamin D deficiency. Though nothing conclusive can be said about his diet, we can infer that his dark skin was not adaptive to his new environment. His body was simply not absorbing enough vitamin D from sunlight.

What I find particularly interesting from this news article is a snippet of natural selection 500,000 years ago. Depending on where you live geographically, there are selective pressures that select for lighter or darker skin color. Individuals with lighter skin color are better adapted to live further away from the equator while individuals that live close to the equator are better adapted with darker skin tone. This leads me to my question, did the evolution of skin color started in Homo erectus?

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]

Homo Floresiensis: Hobbits of Southeast Asia

What is Homo floresiensis? This question has plagued scientists since the 2003 discovery of these hominids in the remote island of Flores, Indonesia. A few specimens, found only inside the cave of Liang Bua in Flores, were given the names LB1, LB2 and so on. Their small stature, thought to be no taller than a three-year-old human child, led to them being nicknamed “Hobbits” by scientists after J.R.R. Tolkien's tiny “Lord of The Rings” characters. Homo floresiensis is thought to have co-existed with modern humans starting from about 18,000 years ago to about 13,000 years ago -- pretty recent in geological time. What Is The Hobbit?

Height comparison between Homo sapiens sapiens and Homo floresiensis. Illustration from www.amnh.org

Cranial comparison between LB1 (Homo floresiensis) and modern human. Photo from www.bbc.co.uk

A recent article suggests that Homo floresiensis existed alongside modern humans (Homo sapiens sapiens). If Homo floresiensis were indeed contemporaneous to modern humans, then they could have been the sourceof local myths such as the “Ebu Gogo” and “Orang Pendek”. Cryptozoology and mythology aside, scientists are still debating whether Homo floresiensis is a species of its own or just a small population of Homo sapiens sapiens that suffered from cretinism.

Putting a face to the hobbit (Facial reconstruction from LB1 cranial). Photo from www.blogs.discovermagazine.com

So who really were Homo floresiensis? A species of their own or just individuals that suffered from cretinism? We still do not know.

If Homo floresiensis were indeed a species of their own, did they evolve out of Austrolopithecine, Homo erectus or even archaic Homo sapiens?

If Homo floresiensis were actually archaic Homo sapiens suffering from cretinism, how did they survive well pass adulthood and use stone tools to hunt?

Currently there is no consensus whether Homo floresiensis were a separate species or just individuals who suffered from cretinism. What do you think?